Category Archives: Articles

Oxy-acetylene

The equipment was taken out of the company vehicle and set up near to the chiller. Care was taken to ensure that the oxy-acetylene was not in the escape route for our engineer in the event of an accident. The condition of the equipment was inspected and a leak test carried out.

Strip Down during Process Chiller Repair Service

The covers were removed from the location of the expansion valve, the lagging stripped back and the electrical connection removed. The old expansion valve was now ready for removal…

Remove and Replace

Our engineer heated the inlet to the valve until the solder melted and then removed the liquid pipe. He then repeated this on the expansion pipe. Now that the old valve had been removed, he used a specialist tool to clean off the remaining solder and impurities on the refrigerant pipework. Having done this, he fitted the new valve into position. A special heat sink was used to protect the new expansion valve during the brazing operation. Then, the inlet and the outlet pipes were silver soldered into position.

Pressure Testing during Process Chiller Repair Service

The integrity of the entire system was proven by carrying out a nitrogen pressure test according to standard industry guidelines. The customer witnessed the start and the finish of the test and this was recorded on the Pressure Test Certificate.

Dehydration Process during Process Chiller Repair Service

Our engineers carry a powerful 10 cfm vacuum pump as part of the equipment in his car. This pump speeds up the removal of moisture and also non condensables from the system such as air and nitrogen. Our engineer left the process running overnight and returned in the morning to find deep vacuum had been achieved.

Refrigerant Recharge

The correct amount of refrigerant was recharged into the system and the cylinders were returned to the storage area.

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How do Chillers Work? Expansion Valves

System Testing

The controller of this machine automatically gives you the fridge system readings. However, our engineer wanted to fit his own test equipment to the chiller anyway. This was to test that both readings were the same for calibration purposes. Having done this, he ran the system and waited for it to load up to 100%. Then, he took the superheat and the subcooling readings which were found to be within standard industry guidelines.

Clear Site

All of our engineers leave the work location of the chiller in a better condition than before they attended site. Good house husbandry goes a long way to promote the professionalism of a chiller company. The little things are what you, the customer, often notice first as some of the more technical things are not always so obvious.

Paperwork Sign Off

The permit to work was signed off having completed a satisfactory fire watch. Our paperwork was then completed and scanned into Head Office. We like to do this on the day of the job, so your accounts department gets the report promptly and can start processing the Invoice.

Monitoring

Our engineer then gave the chiller a mini service for the rest of the day. All readings were taken on both of the refrigerant systems and compared to the Tick Sheet of the previous maintenance visit. This was to see if there was a deterioration of any of the readings over a period of time. Small problems would show up before they turned into big problems. This is just another way of how we at Maximus Chillers saves you money.

Courtesy Visit

Just to make sure that the machine had settled down satisfactorily and that there were no further issues- our office arranged a courtesy visit a few days later. The chiller system was still operating as it should and there were no other faults to report.

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Chilled Water System EEV Service

Tags : air cooled chiller condensers centrifugal chiller compressors chiller compressor systems chiller condenser fans chiller condenser high pressure control chiller condenser high pressure faults chiller condenser systems chiller fan deck replacement chiller refrigerant leaks chiller refrigerant system vibration eliminators leaking chiller condensers maximus advantage reciprocating chiller compressors screw chiller compressors scroll chiller compressors

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Read more about electronic expansion valves on the Carel website.

27/03/2022
Maximus Chillers
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Chiller Repair Service

Category : Articles

An effective chiller repair service is what you need to get you up and running- fast! Here at Maximus Chillers, no job is too small, or too big. We have the capability to do anything from replacing contactors to centrifugal compressor remanufacturing- we are a one stop shop for all of your needs.

News Article No.26

Customer Orientated Chiller Repair Service

We also know the reason why we are an expanding company: you- the customer! Listening to your requirements goes a long way to help us achieve your objectives. We assign the same engineer to each site, so that you have the chance to build up a relationship and he gets to know your plant. Read on for an insight into some of the repairs that we carry out…

All new fan decks in place on large air cooled chiller during chiller repair service

Fast supply chain for retrofitting fans

Fan Deck Retrofitting Chiller Repair Service

The photos show the fans being lifted up, then when they are in position on a 200kw ammonia chiller. The fans had been failing one at a time until the chiller started experiencing high pressure trip outs. Action was not immediately taken because there were insufficient funds in the customer’s budget. When the customer was allocated a new budget, they gave us the Order to carry out the work. We decided to change all 8 fans.

Odd Size

The old fans were 790mm blade diameter instead of the standard 800mm. Manufacturers ask suppliers for odd sizes and specifications along with an OEM data plate in an attempt to monopolise the customer. A bonafide chiller company, however, is adept at making square pegs fit round holes. Not really a round hole though with this one- we just plonked our fan decks on top where the old ones had been fitted.

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Refrigerant Leak Chiller Repair Service

HFC refrigerants are becoming more expensive due to the HFC phase down. Therefore, as well as the environmental cost of a leaking chiller, there is the cost on your pocket too. At Maximus Chillers we find the root cause of the leak instead of just brazing it up. Some of these causes are:

Condenser Vibration

Some head pressure control systems bring the fans on, forwards and backwards in different stages. This causes the chiller frame to judder and vibration related leaks to occur on the condenser. The solution is easy- fit stand alone fan speed controllers.

Compressor Vibration

Some chillers are designed to fit into a small footprint of space. A good example of this is a particular model of laser chiller that had been designed to fit down the side of a laser cutter. That’s alright until, years after production, reoccurring leaks start happening around the compressor. There is no room to fit vibration eliminators, besides, they only work if they are fitted horizontally and vertically with the far end being clamped. Brazing the leak up just causes the already work hardened copper pipe to further anneal and become even more brittle- another leak will happen shortly there after. The solution is to remove the whole piece of pipework, go up a pipe size and replace it with new.

Component Failure

We find some components are flawed and are prone to leaking. An example of this are refrigerant hoses which are prone to rubbing through against the chiller. The solution is to fit anacondas or static copper pipework.

Reduced Service Costs

All of these measures and more are how we reduce the frequency of refrigerant leaks on your plant.

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How do Chillers Work? Compressors

Compressor Remanufacturing Chiller Repair Service

Weather you have scroll, reciprocating, screw or centrifugal compressors, we have the capability to get it out, rebuild it and get it back in again. With same day delivery of internal compressor components- we won’t keep you waiting around. Our expert team are adept at ensuring that your compressors are rebuilt with minimal run out and have clearances that are within tolerance. All bolts are touqued up to the correct setting too. The last part of the job is the compressor paint re spray to the same colour as before, or to our standard battleship grey.

Controls Retrofitting Chiller Repair Service

When a controller fails it is often found to be obsolete. Don’t worry because we can fit a new controller to any machine. For HFC chillers we fit Carel controllers, we fit Beijer Electronics to ammonia chillers and MCS controllers to centrifugal chillers.

Strip Out

The easiest way to do a controls retrofit is to start all over again from scratch. We remove the defunct controls from the panel and pull all the control wiring out too. We leave the three phase wiring in place, the contactors and the common neutral.

Rewire

One wire at a time, we rewire the chiller. All of the analogue inputs are wired in along with the digital inputs. Then, the outputs are wired to the contactors and relays. The transformers in the panel are often reused to get the various voltages that are required for the new controller, contactor coils and relay coils.

Commissioning

The new controllers come pre set with default parameters so only minor adjustments are needed to get the chiller to settle down. We then spend the rest of the day monitoring the chiller so as to watch it running in the various stages of loading and under different running conditions.

Chiller Repair Service that is Second to None

The above examples are just an insight into our extensive range of capabilities in the repairs of your plant. Basically- if you have a problem- then we have a solution. This is just part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. With customers around the world in places like Saudi Arabia, Spain and the United States of Amarica we continue to exceed the expectations of our customers. We have a network of engineers around the UK too, so we are never farer than a couple of hours away. For the best service, the choice is clear- Maximus Chillers!

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13/02/2022
Maximus Chillers
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Chiller Maintenance Service

Tags : chiller compressor oil change chiller condenser fans chiller condenser high pressure faults chiller condenser systems chiller control systems chiller evaporators reciprocating chiller compressors shell and tube chiller evaporators tighten chiller wiring

Category : Articles

Maximus Chillers have just carried out our quarterly chiller maintenance service at a factory in the North West. We look after 6MW of cooling across 12 industrial process chillers. This was a minor visit, so no need for oil changes and checking the head gear on the reciprocating compressors. Instead, we took oil samples which we analysed in our laboratory. Read on for an insight into our engineer’s findings on each of the chillers…

News Article No.25

Chiller 1 Maintenance Service

System 1 has a compressor that had blown all three of the 200 amp centred tag fuses. On inspection with a multimeter, our engineer found a dead short to earth on the internal electric motor. We have submitted a Quote for the lift and shift, remanufacturing at our facility, then the lift back in. Several oil changes will then be carried out at planned intervals.

Chiller 2

More or less textbook readings were taken and no problems to report.

Chiller 3 Maintenance Service

Slightly poor readings were taken on the low side of all 4 of the systems. This issue has now been flagged in our system for monitoring. If it deteriorates, we will submit a Quote to take the evaporator end plates off and carry out a chiller tube cleaning operation.

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Chiller 4 Maintenance Service

Compressor 3 has had an issue that has been developing over a period of time. Occasionally, it throws the breaker, then when the electrical readings are taken- they all check out okay. The contactor condition had been inspected, the wiring and motor connectors had all been tightened up too. Shortly before the visit, our customer rang to say “Chiller 4 has gone for a Burton!” When we attended the call out, we found the contactor had blown against the inside of the panel. We have submitted a Quotation for the replacement.

Chiller 5

System 2 had a flashing sight glass in some conditions, but the other fridge readings were okay.

Chiller 6

This system had low side readings similar to Chiller 3. Again, they were not deemed to be an issue yet, but if we decide to do a chiller tube cleaning operation, we will prepare one Quote for both chillers.

Chiller 7

No problems to report.

Chiller 8

Only a short run was available due to the process load conditions, but no problems were found by our engineer.

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Planned Preventative Chiller Maintenance

Chiller 9 Maintenance Service

All the way through to chiller 9 and the fault finding was easy, now this: external interlock alarm. When our engineer logged the issue with our Technical Support Desk using our real time app on his phone, he stated that to his knowledge, there were no external interlocks.

Fan Motors

Therefore, he decided to check the fan motor overload switches. All 5 fans on each system are linked together in series, so he looked for the volt feedback in the panel for System 1 and System 2- this checked out okay.

External Switch

Therefore, he decided to look for an external switch as the fault suggests. He walked along the gantry and down into the plant room below the chillers...

Pump Set Panel

There is a panel that controls the chilled water pump sets. No wire from the chiller was found to go into this panel.

Remote Monitoring Panel

This is a display that conveys the running condition of the chiller down to the plant room below. It saves a process engineer from having to go up the stairs and onto the chiller gantry. This panel is indeed connected to the chiller with electrical wiring. However, no switch was found that could have caused this fault.

Buffer Vessel

A 10,000 ltr buffer vessel is also located in the plant room. As it is open to atmosphere, our engineer looked for a low level switch which may have tripped- no switch was found.

Program Settings

Now that anything external to the chiller had been eliminated, our engineer decided that the fault must indeed be coming from inside the machine. Because the fan overloads had checked out okay, he decided to have a look at the program settings...

Extensive Library

We have an extensive library of manuals and passwords for all chillers. We also have a network of engineers around the country- one of them will know someone who will has a manual or password. When our engineer contacted our Technical Support Desk real time through his app- the manual and passwords were sent to his phone. He found the menu level and parameter for external interlocks which was found to be wrong. To our knowledge, our customer does not have the password for this chiller. The process had been off for some time due to system upgrades with contractors on site doing other work. They could have changed the setting for some reason. We don’t know- but at least the setting was corrected and the chiller came out of fault.

Chiller 10

This chiller uses belts to drive the fans. On inspection, several of them were found to be in poor condition or broken off. We have just replenished the stock of spare fan belts on site, so our engineer replaced them, then tested each fan motor in turn.

Chiller 11

This is the same make and model as Chiller 10. The same issue was found and then rectified.

Chiller 12 Maintenance Service

This chiller is in a part of the factory where the environment is very dusty. Therefore, a blocked condenser and high pressure cut outs are common place. The process engineers are aware of this issue, so they keep on top of the maintenance of the condenser. If the condenser does deteriorate- they know how to reset the fault. No problems were found with this machine.

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Tags : chiller condenser high pressure faults chiller condenser systems chiller evaporators flooded chiller evaporators shell and tube chiller condensers shell and tube chiller evaporators

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Read more about buffer vessels at Fabricated Products.

23/01/2022
Maximus Chillers
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Far end plate removed to show the tubes in the shell of a condenser

Chiller Tube Cleaning Service

Category : Articles

Our chiller tube cleaning service will improve the efficiency of your plant by up to 30% This is because the dirt on your copper tubes causes thermal insulation which prevents heat transfer. The chiller will therefore load up and stay on longer to achieve the same amount of cooling. Eventually, you will start seeing error messages such as discharge limiting and then a high pressure cut out. Loss of production, or staff walking out of a hot building can easily be prevented through our services…

News Article No.24

Chiller Condenser Tube Cleaning Service

We attended site to carry out the full overhaul of 4 chiller condensers for a customer of ours in Manchester. Our engineer signed in and completed the Permit to Work which was issued by the onsite maintenance engineer.

Risk Assessment Method Statement

The necessary Risk Assessment Method Statement was emailed in PDF format in advance. Our engineer carried out a short site survey of the work location to check if there were any additional risks that were not included in the RAMS. All was okay, but we have an amendments section if there were any additional risks.

Chiller Isolation

Chiller 2 was found to be in standby, so our engineer decided to start with that chiller. The grey toggle switch was turned from the 1 position to the 0 position. He then down powered the control panel. Having done this, he reconfigured the water system butterfly valves to prevent potential failure of the other condensers. Then, he valved off the Water In and Water Out butterfly valves and drained down the condenser.

Unbolt the End Plate

The bolts were removed and the end plate was moved to the side.

Inspection

The photo shows the condenser tubes being inspected. The bottom half of the tubes flow into the end plate and the top half of the tubes return to the other end. You can see red foreign objects blocking the tubes and lowering efficiency.

Equipment for Chiller Tube Cleaning Service

The loose objects were easily removed, but the real difficulty was removing the dirt from the inside of the tubes. We have state of the art tube cleaning equipment which is suitable for normal and internally enhanced tubes. We worked on each tube in turn until the dirt was removed, then we rinsed them all out.

Reassembly

The end plate seal was replaced with our specialist seal kit which we keep on the shelf in our stores. This replacement was required to ensure there would be no leaks when full system pressure was reintroduced into the condenser. Then, the end plate bolts were tightened up to the correct torque setting.

Testing

The final step was to reconfigure the water system butterfly valves ready for the next system. This done, the Water In and Water Out valves were opened and the condenser was purged of air. The chiller was started up and dramatically improved system readings were recorded. It was calculated that this chiller alone was now consuming 23% less electricity than before the job.

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Shell & Tube Chiller Condenser Cleaning Service

Midde East

We have a store in Jeddah, Saudi Arabia for our shell and tube chiller condenser cleaning equipment which we use for our customers in the Middle East. We arrange the shipping from Jeddah to our customers who are mainly in Riyadh, The United Arab Emirates and Oman. We also have some customers in Bahrain and Qatar.

Saudi Arabia

The visit to Saudi requires our overseas engineer to have had 3 Covid jabs which are recorded on his NHS Pass. The QR code expires, so it needs to be updated shortly before the trip. Then, the NHS pass has to be uploaded onto the Muqeem Portal. This is a Saudi verification portal to check if an engineer is vaccinated. Having done this, the Tawakkalna app is enabled in his phone which allows entry to public buildings and the factory he will be attending. To obtain the VISA, our site contact has to invite our engineer to the Kingdom as a guest. The VISA process is quite complicated, so we use a company in London to guide us through the process from start to finish.

Site Assistance

This kind of work is a lot easier with a second man to assist. When working in the Middle East, the factory or facility provides us with one of their onsite engineers to help with the manual handling. It is a lot quicker with another engineer to help set up and then stow away the equipment.

United Kingdom

In the UK, we keep our tube cleaning equipment at Head Office. Prior to a site visit, we palletise, then ship the equipment to the customer’s location. We charge the same price to all of our customers anywhere in the UK. This is because we have a network of engineers around the country who are no more than 2 hours travel time to your location. We have a lot of customers in the North West of England, the West Midlands and London. We also have customers in out of the way places, such as, Aberystwyth.

0161 370 7193

service@maximuschillers.com

Improve Chiller Efficiency

Chiller Evaporator Tube Cleaning Service

The evaporator of a chiller is less often fouled as the chilled water system is not exposed to a water tower. Therefore, we carry out evaporator cleaning less frequently. We carry out an extensive set of tests during the maintenance to assess the efficiency of chiller evaporators. When the readings are poor, we recommend our tube cleaning service. The process is exactly the same as described above. Often, our customers ask us to clean both heat exchangers on a chiller as this reduces the cost of cleaning them separately at different times.

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Read more about Chiller Condensers on The Engineering Mindset.

07/12/2021
Maximus Chillers
-

Chiller Failure

Tags : chiller compressor failure chiller compressor lift and shift chiller compressor oil level chiller compressor unloading chiller expansion valves chiller nitrogen pressure tests chiller pipework oxy-acetylene brazing chiller refrigerant economizers chiller refrigerant leaks chiller refrigerant subcooling chiller refrigerant superheat chiller refrigerant system vacuum pumps f-gas chiller leak testing procedure low refrigerant pressure faults refrigerant system dehydration process shell and tube chiller evaporators

Category : Articles

Chiller failure can be expensive and even result in buying a new, or refurbished chiller. Read below to have a look at two different scenarios…

News Article No.23

F-gas Chiller Failure

We carry out regular f-gas leak tests at periodic intervals to prevent unnecessary refrigerant leaks to atmosphere. This leak, however, occurred in between tests and was alerted to us by the factory personnel. They had noticed icing up, near to a solenoid coil due to liquid refrigerant leaking and then boiling off.

Leaking Solenoid Valve

The plant had failed due to the stem of a solenoid valve splitting at the base and causing a refrigerant leak. The valve provides a bypass of liquid refrigerant to the economizer. This is used to further subcool the rest of the liquid refrigerant before it enters the expansion valve. This subcooling improves the COP (coefficient of performance) and so reduces electricity costs.

Decant during Chiller Failure

When our engineer attended site, he decanted the remaining refrigerant into recovery cylinders which were weighed, adding the TARE weight into the calculation.

Remove and Replace

The same size solenoid valve was sourced from the suppliers. The area was cleaned up using an emery cloth and a wire brush, then the valve was brazed into position using oxy-acetylene.

Nitrogen Pressure Test

The system was then put on pressure test according to industry guidelines with the customer witnessing the start and the finish. The result was satisfactory, so this was recorded on the pressure test certificate. The certificate was filed with other chiller paperwork which is available for inspection by external auditors.

Dehydration during Chiller Failure

The picture was taken during the refrigerant leak repair in this article. You can see the gauge pulled down to 2 Torr of a vacuum. This was after an overnight dehydration process.

Recharge and Switch On

The refrigerant was recharged into the system until the superheat and subcooling values came to within standard industry guidelines. The plant had sufficient load to run at 100% for an extended period which was a good opportunity to monitor the compressor temperature and the oil return. Eventually, the compressor unloaded to match the demand coming from the process.

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Chiller Failure due to Evaporator Freeze Up

A new customer of ours had not had a maintenance contract for some time. This section emphasises just how important PPM (planned preventative maintenance) is. During these visits we carry out checks and tests to the various components that protect the evaporator.

Flow Switch causing Chiller Failure

This component was found to have failed which allowed the compressor to carry on running when the pump had gone off.

Water Out Sensor

Another safety device on this machine is the Water Out sensor. Because of the way that this chiller had failed, however, this sensor was reading high while the inside of the evaporator was freezing up.

Buckle and Burst

Ice has a larger size than water due to how the atoms form into a crystalline structure when freezing. This caused a catastrophic failure in the evaporator. The copper tubes in the evaporator shell started to bend then buckle. Eventually, a proportion of the pipes bust which caused the refrigerant to leak into the water system.

Low Pressure Switch

The compressor low pressure switch did not activate. This was because the refrigerant had leaked down to the same pressure as in the water system, then the water was sucked into the chiller.

Compressor Smash Up

As a compressor cannot compress a liquid, the water damaged the bearings and then a smash up occurred.

Condenser

While this was happening, the water in the refrigerant system continued to the condenser and so the whole system was ruined.

What a Mess!

As you can see from the above, there couldn’t be a worse thing that could happen to a chiller. Regular maintenance was all that was needed to prevent this. Give our Technical Support Desk a bell to discuss our range of maintenance packages that will keep your chillers running in the best condition.

0161 370 7193

service@maximuschillers.com

Pick up the Pieces after Chiller Failure

After the above failure occurred, it was a big job to pick up the pieces…

Compressor

The compressor needed to be lift and shifted to our remanufacturing facility at Head Office for a full strip down, inspection and clean out. Then, a list of parts was composed for the rebuild. When the parts arrived, the compressor was rebuilt making sure that the clearance of the bearings and the run out of the shaft were within industry guidelines. All of the internal bolts were torqued to the correct value which was recorded on our remanufacturing sheet. A lick of paint was applied and then the compressor was shipped back to site.

Components

All of the components around the system were replaced or dried out, then the compressor was lifted back in with the suction and discharge valves closed. This was to prevent the moisture in the system from ingressing into the newly rebuilt compressor.

Dehydration

An industrial vacuum pump was used which carried a changeable oil filter. Our system dehydrating vacuum pump came on a skid which was located next to the chiller. We used a ¾” refrigerant hose that was fitted to the same size service port on the chiller. This prevented any pressure drop in between the vacuum pump and the refrigerant system.

Oil Filter Changes after Chiller Failure

The moisture being removed from the system went into the oil filter which caused it to block. Therefore, the oil filter needed to be changed daily at the start of the process and then less often towards the end. We also use a special catching device depending on how much water there is in a system that needs to be removed.

Torr Gauge

The Torr gauge dropped quickly at the start of this process until it reached the saturation point of water. At this point it stopped until the water was removed and only vapour was left in the system. Then, the Torr gauge started to slowly drop down to 2 Torr.

All of this article was due to a lack of routine maintenance!

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03/12/2021
Maximus Chillers
-

Chiller Call Out

Tags : chiller condenser high pressure faults chiller condenser high pressure switches chiller control panels chiller electrical faults chiller fault finding chiller n+1 redundancy chiller refrigerant leaks low chiller refrigerant charge low refrigerant pressure faults

Category : Articles

Chiller call out is the essence of what a company like Maximus Chillers is all about. It is a time when our engineers come into their own. Read on to see examples of how we do it…

News Article No.22

Chiller Call Out for Ammonia Leak Alarm

At first sight this appears to be a dangerous situation as ammonia is very harmful to human health. This is because of its corrosive and toxic characteristics. Each of our engineers carries breathing apparatus and full length ammonia PPE should it be required.

Location Assessment

The work location in the photo is assessed using an NH3 detector. This is sensitive enough to detect lower than the 35 parts per million short term exposure limit. The detector is fitted to the work wear of our engineers whilst near to the plant. When the alarm does not sound and there is no smell of ammonia- it is safe to proceed.

Electrical Fault

Usually this alarm is due to a controls issue rather than a leak. There are various reasons:

UPS and Alarm System Malfunctions

Chiller panels for this kind of plant have a UPS (uninterruptible power supply) This is a battery which is charged by the mains. When a power failure occurs, the charge in the battery supplies 240v to the ammonia alarm. This means that the chiller continues to be protected. When malfunctions occur to the UPS or the alarm system, the yellow warning light and siren is activated which needs to be manually reset.

Sensor Failure

The sensors have to be calibrated at regular intervals. The base setting of 0 parts per million has to be set and then the trip outs of 35 and 25 parts per million. These sensors can be knocked out of calibration by small leaks over a long period of time, or they can malfunction internally. If you require the service of your leak alarm- email our Technical Support Desk and will arrange a site visit.

0161 370 7193

service@maximuschillers.com

Chiller Call Out for BMS Failure

Chillers can get blamed for everything as the customer can notice a building that is getting warm and then call us out. An example of this is when a new customer of ours signed up to a maintenance contract after a long period of neglect. They did so because the office workers in a large office block had started to leave their desks and walk out of the building.

Investigation

When our engineer attended site, he found various faults with a row of four, 500 kW chillers on the roof. There was found to be N+1 redundancy built in, so he considered there to be sufficient cooling available to satisfy demand.

No Run Signal

Despite there being available load, the chillers were not being given the run signal from the BMS. The toggle switches on the BMS panel did not give the run signal to the chillers when they were put into Hand. This was found to be because of other issues with the poorly maintained panel.

Link Out

Our engineer therefore decided to link out each of the chillers in their respective panels. He consulted the wiring diagram and made the modifications accordingly. He then entered the password for that particular chiller and adjusted the program settings. These changes made the chillers stand alone and not reliant on the BMS run signal.

Chiller Call Out for Pump Sets

The pump sets were also found to be in poor condition. There were found to be failed pumps, blown contactors and defunct controls. The good news was that by changing components in the panel, he managed to get at least one of each pair of pumps going for the various water systems used around the building.

Pressurisation Unit

This is a machine with an internal pump and a pressure switch which is used to maintain the pressure of the water system. Both the run and the standby pumps were found to have failed with other component failure in the unit as well. Our engineer decided to manually fill the water system with mains water to build up the pressure.

Get it Away

Having done all this, our engineer got the chillers away and watched the water temperature come down from 24°C to 6°C. As the chiller systems came down to set point, they unloaded to match the demand from the building.

Return to Work

The office staff started to return into the building and resumed work at their desks.

0161 370 7193

service@maximuschillers.com

Fault Finding during Chiller Call Out

Now that the pressure was off, our engineer carried out the necessary fault finding to the systems that had failed:

Refrigerant Leaks

Three of the systems were found to be locked out with low pressure alarms. He assessed the quantity of recovery cylinders and refrigerant that was required. Then, he submitted a report to Head Office for a return visit to carry out the repairs.

Blocked Condensers

Some of the systems were found to have blocked condensers. The call out was during the summer when a high pressure condition was more likely to occur. A build up of contaminants had reduced air flow and caused the high pressure switches to be activated. We arranged a site visit with a special cleaning agent to remove the contaminants and restore the air flow through the condenser fins.

Chiller Call Out for Flow Switches

These are a switch used to detect water flow and two of them were found to have had failed. There are various types for different applications. We select a suitable flow switch and then make the necessary adjustments to the internal control screws. This ensures that the switch will function correctly when problems with the water system occur.

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F-gas Chiller Leak Testing

Tags : chiller control panels chiller control systems chiller electrical faults f-gas chiller leak testing procedure r134a chiller refrigerant r407c chiller refrigerant

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29/11/2021
Maximus Chillers
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Humorous display of various sizes of nails to use as fuses to solve chiller problems

Troubleshooting Chiller Problems

Category : Articles

We have a lot of enquiries from our subscribers about troubleshooting chiller problems, so read below for an insight into three commonly occurring issues that are detrimental to the environment…

News Article No.21

Troubleshooting Chiller Problems for Blown Fuses

Although the photograph is funny, not using fuses or using the wrong fuses will result in a fire. When a component burns out and the volts go to earth, the component draws more amps until the fuse blows. Fuses are therefore sized to have a slightly higher amp rating than the running amps of the component. Poorly running chillers with blown fuses and worn out components run inefficiently and so are bad for the environment.

Slow Blow

These fuses are also called motor rated fuses. As the name suggests, they are designed to be used with motors. Motors pull a lot of amps on start up, then settle down to their running amps. The delay before the blow allows for this initial spike of amps. Chillers use motors for:

Condenser Fans

These fans can be radial in design which are driven by a fan belt and motor. They can also be axial with the motor integral at the centre of the impellor.

Water System Pumps

The motor is bolted onto a flange at the back of the pump housing. This means that the replacement is easy as the pump housing remains bolted to the chiller.

Oil Pumps

On centrifugal and screw compressors a motor is often used to drive an oil pump. This sucks oil from the sump and into the compressor bearings to pre lubricate them, therefore preventing untimely bearing wear. Once the compressor is running, the pump motor drops out.

Compressors

Compressors use 2 kinds of electric motor:

Open Drive

An open drive motor can be clamped to a compressor housing. The motor shaft is clamped to the compressor crankshaft using a coupling.

Hermetic and Semi Hermetic

With this design, the motor is located inside of the compressor. An advantage of this is that the motor is cooled by the refrigerant returning back to the compressor.

Refrigerant Pumps

Ammonia systems have all of the liquid refrigerant stored in a low pressure receiver. Motors are used to drive liquid pumps which discharge the refrigerant into the evaporator.

Mobile Workshops

Each of our company cars carries a full complement of cartridge, bottle and centred tag fuses. This means that we can isolate the failed electrical component, replace any fuses and get you up and running whilst on site. We will then arrange the delivery and replacement of the failed component.

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Troubleshooting Chiller Problems for Refrigerant Leaks

HFC

Because of the high GWP (global warming potential) of HFC (Hydrofluorocarbon) refrigerants, gas leaks are very damaging to the environment. R407c is often used in large air cooled chillers and R134a is often used in centrifugal chillers. The heat trapping qualities of these refrigerants adds significantly to global warming.

Training

Therefore, all of our engineers attend 3 years at college with a refrigerant handling course at the end. The environmental regulations that are studied are…

The Monreal Protocol

This protocol came into force on the 1st January 1989. It was devised to protect the ozone layer by phasing out ozone depleting substances. In chillers, these substances take the form of HCFCs, such as, R22. Most of this refrigerant no longer exists in chillers due to a service ban preventing the repair of the plant. This meant that when problems occurred, the refrigerant had to be decanted and recycled. The chiller was then decommissioned. In some overseas countries there are still systems running on R22. In small systems it still exists too, where no service has been carried out.

Kyoto Protocol

This protocol came into force on the 16th February 2005 and is concerned with the reduction of greenhouse gas emissions that lead to global warming. In our industry, adjustments and procedures to improve chiller efficiency significantly reduce the consumption of electricity.

F-gas Leak Testing

This is a periodic leak test that is carried out to detect a leak that has occurred before the whole charge of refrigerant has been lost to atmosphere. We have written a detailed news article on this subject called F-gas Chiller Leak Testing

Ammonia

This refrigerant has a GWP value of zero: it does not add to global warming. It is highly corrosive and toxic, so specialist equipment and training is required to handle it.

HFO

Hydrofluoro-olefin refrigerants are becoming increasingly popular in newer chillers. They have a very low GWP, but they are still expensive due to the cost of their research and development. The downside is that when they leak, they work their way through the weather system and into the sea where they are harmful to aquatic life.

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Tags : air cooled chiller condensers chiller condenser replacement chiller diagnosis chiller fault finding f-gas chiller leak testing procedure

Troubleshooting Chiller Controls Problems by Retrofitting

A big chiller problem is when the controls fail and they are found to be obsolete. The manufacture of a new chiller has a massive carbon footprint. Therefore, keeping the current chiller going is the most environmentally friendly option.

Refurbishment

We can refurbish your controller in our electronics laboratory. This is a simple process as we disconnect the controller form the chiller and weatherproof the chiller panel. Once on the bench in the lab, we strip it down for inspection. Often the problem is obvious: dust on the back of the PCB can ‘track’ volts to the wrong part of the board. This can cause component failure to occur. We resolder any failed components and remove the dust from the PCB. On arrival back on site, it is an easy job of just removing the weatherproofing and re connecting the controller.

Controls Upgrade

Alternatively, we can fit a new controller all together. We are on account with MCS for centrifugal controls retrofits, Beijer Electronics for ammonia systems and Carel for most other chillers. This process is more complicated and takes about a week…

Remove and Replace

The old controller and associated wiring is removed from the chiller. Then, the new controller is fitted to the panel and the power supply wires connected.

Inputs

The digital inputs, such as the flow switch are connected. Then, the analogue inputs, such as the pressure transducers are connected.

Outputs

The digital outputs, such as the compressor run signal, are connected.

Commissioning

When the above process is complete, the chiller is switched on and the controller parameters are commissioned. On run testing the chiller, the parameters are further adjusted until the machine goes into seamless operation.

Chiller Maintenance Contract

Category : Articles

In this article we will be looking into a chiller maintenance contract- how it is composed and examples of how it is put into practice in the field.

News Article No.20

Chiller Maintenance Contract Schedule

This part of the contract details:

Asset list

According to F-gas regulations, each site has to compile an asset list of the plant containing refrigerant. The asset number, model number, serial number, refrigerant type and quantity have to be recorded on this list. It usually takes the form of a file in the facilities manager’s office and is available for inspection by external auditors. Read more about F-gas chiller leak testing

Procedures

Depending on the type of plant onsite, the set of procedures and testing varies. These procedures are used to extend the life of your chillers and improve their efficiency. Read more about chiller efficiency

Tailor Made

These are procedures specific to a particular chiller. They vary from checking the condition of condenser fan belts to changing oil filters. A walk round of the plant is carried out prior to writing the maintenance schedule. This ensures that the individual requirements needed for each chiller are met.

General

These are procedures that apply to all chillers and include the above mentioned F-gas leak testing and refrigerant charge health check. We carry out over 100 checks and procedures to any chiller during the maintenance.

Frequency

Depending on redundant systems being available and how much load there is to the plant, the required frequency of visits varies. Each year we recommend at least 2 visits for small process chillers, 3 visits for large air cooled chillers, 4 visits for ammonia and monthly visits for centrifugal chillers. Read more about chiller maintenance schedules

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Fault Finding

Carrying out the above procedures also highlights the faults. We carry out the fault finding and diagnosis of your chillers whilst on site. This reduces your costs by removing the need for separate call outs.

Mobile Workshops

We also carry an extensive range of materials in our company cars which we use as mobile workshops. This means that we often get a chiller running at no extra cost- just another way we provide you- the customer with a service that is second to none. Read more about fault finding and diagnosis

Tick Sheet

We have spent years developing a Tick Sheet that, we believe, is the best in our industry. It is one sheet for all chillers, so our engineers become accustomed to where each check is listed on the sheet. Checks that are not relevant to a particular machine are crossed out. Read about the maintenance checklist that you can carry out in between visits.

Chiller Maintenance Contract Terms and Conditions

This part of the contract outlines our charges and terms. We are very customer oriented, so we have written our terms and conditions to work well for both parties. At the end of the day, we are on your side and we will bend over backwards to provide you with the best service.

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Chiller Troubleshooting

Chiller Maintenance Contract in Moscow

An example of one of our maintenance contracts is for an overseas customer in Moscow. We have a three year contract because this gives them the assurance that the price will not go up each year. It also gives us the time to plan longer term into the upkeep of the chillers.

Water Cooled Chillers

The main building is cooled by three water cooled chillers. The condenser water system goes up to a row of dry coolers on the roof. The plant is only needed in the summer as Moscow has very cold winters. Therefore, to save the customer from having to drain the water system down each year- glycol is used. We have a specialist test instrument to check the glycol percentage on each visit.

Air Cooled Chillers

There are various air cooled chillers at two sites which are located in plant rooms with ductwork for the condensers. This is so that when the chillers are shut down for the winter, they are protected from the inclement weather. The compressor oil is kept heated with crankcase heaters. This ensures that the compressor bearing life is not reduced during start up after the winter.

Laboratory Chiller Maintenance Contract

The chiller in the photo is used to provide a narrow deadband of temperature to a laboratory in the North West. The fan coils in the building also have the effect of dehumidifying the air. Separate humidifiers are available to control the humidity to 50% RH. A small loss of water occurs from around the building, so a pressurisation unit is available to keep the pressure at a pre determined level. Mains water can be added to the water system to bypass the pressurisation unit for a quicker water system top up.

Retrofit and Rebuild

We have fitted a new condenser which we manufactured bespoke. We also have the capability to retrofit the evaporator and rebuild the compressor. Read more about our compressor remanufacturing facility

Laser Chiller Maintenance Contract

One of our customers has a laser chiller at a site in Cumbria. It is used to cool down an American made laser cutter for the fabrication of sheet metal. They have a high production volume to keep up with, so it is imperative that the chiller is maintained to the highest standard. Non destructive testing is used so as not to disturb the process. As it is a dusty environment, the main issue on every visit is to change the filter media used to protect the condenser. Read more about how we maintain laser chillers

Global Chilled Water System Service

Saudi Chiller Commissioning

Chiller Maintenance Service

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31/10/2021
Maximus Chillers
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Troubleshooting of a chiller panel on a system running on ammonia refrigerant

Chiller Troubleshooting

Tags : chiller compressor oil change chiller compressor oil level chiller compressor oil pumps chiller compressor oil recovery chiller compressor slide valves chiller diagnosis chiller fault finding chiller refrigerant economizers screw compressor slide valve potentiometers

Category : Articles

In this article a bespoke chiller with ammonia refrigerant is having troubleshooting carried out to identify the faults. Read below to have a look into the various issues that commonly occur on this machine…

News Article No.19

Chiller Troubleshooting of Low Oil Level

There are times when this machine experiences a low load condition. This is because another chiller is also available as well as free cooling.

Building Management System

The BMS regulates the sequencing of the chillers, the pump sets, the water system valves and the free cooling. We found after troubleshooting that, especially in the winter, the BMS can be slow to react. This causes the chiller to continue running with low load.

Slide Valve at 0%

During a low load condition, the compressor has been designed to run with the slide valve at 0% to prevent too many start ups. These start ups would cause a higher amount of electricity to be used because of the amps being drawn to get the compressor going. Although the compressor uses star/ delta contactors which are a soft start, the repeated starts would still draw a lot more amps. Therefore, the compressor continuing to run at 0% is a lot more efficient.

Oil Pump and Oil Level

When this condition occurs, however, the oil pump continues to suck and then discharge the oil. Eventually, the level in the oil separator drops to below the oil level switch and the alarm is triggered. The photo shows this switch which is a float on a stem. The circuit is completed when the float is at the top of the stem. When the float slides down the stem- this triggers the alarm.

Stainless steel oil level switch removed from the chiller showing the float and the stem

The switch protects the compressor

The Repair

Specialist ammonia resistant personal protective equipment, or PPE is donned by our engineers. Then, ammonia grade oil is pumped in so as to complete the circuit of the switch. After a start up, the same amount of oil has to be taken back out at the other end of the system using the dead man’s valve. This is a valve on the bottom of the economizer which shuts by itself using a spring.

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Chiller Troubleshooting of Oil Filter Differential

When this alarm occurs, you can see the discharge pressure remain at 8 bar and the pressure after the oil filter slowly drop off to less than 6 bar. When interrogating the program, the oil pressure differential trip out is set to 2 bar. After this differential is exceeded, a timer starts to prevent spurious trip outs occurring if the differential pressure is exceeded momentarily. If the differential pressure continues to be exceeded after the timer has timed out- the machine goes into a fault condition which needs a manual reset.

Chiller Troubleshooting Inspection

When removing the cover for the compressor enclosure, the discharge oil pipe can be seen going into the oil filter. An oil pressure transducer can be seen on the far side of the filter.

Contaminants

After the above troubleshooting, it was found that with this kind of system, the oil becomes contaminated with sludge and debris from around the system. Over time this builds up behind the oil filter and so causes the trip out.

The Repair

The repair requires the oil filter to be valved off on either side. Then, full length PPE suitable for the handling of ammonia is required along with beathing apparatus. Each of our engineers carries a portable ammonia alarm and state of the art ammonia handling equipment. We also produce our own ammonia oil filters which we keep on the shelf at Head Office. Give our Technical Support Desk a bell for further assistance.

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Chiller Troubleshooting of Slide Valve Potentiometer

This is a 4-20mA sensor which detects the position of the slide valve. 4mA being shut and 20mA being open. We attended a call out to troubleshoot the alarm message of “slide valve failed to reach the closed position” There is a spring on the end of the slide valve which is used to push it to the closed position when the compressor is off. We decided to activate the drain and fill solenoids which are used to open and close the slide valve. Still the same fault persisted. Having decided that the slide valve was indeed at its closed position, we decided to calibrate the closed and also the open position of the valve.

The Repair

The compressor was valved off and our engineer donned the necessary PPE. The sensor stem was removed from the end of the spring which is attached to the slide valve. A lock nut is available to hold the stem at the required position. This was found to have vibrated loose and so causing the problem. The correct length was set on the stem and the lock nut was re tightened. After rebuilding the end of the compressor, the valves were opened and the compressor checked for leaks. Then, the system was run tested using the manual load and unload buttons on the controller. A good read back was recorded and the machine went into seamless operation.

Chiller Troubleshooting of Ammonia Leak Detection System

This device is stand alone from the chiller and has its own uninterruptable power supply. This UPS is needed so that when there is a power failure to the building, the alarm would still function. There are 2 toxic gas sensors and 2 fire detectors fitted in different locations on the chiller.

Out of Calibration

When we took over the contract 5 years ago, the chiller had been in fault for some time with a leaking shaft seal. After troubleshooting the problem, we found that the small amount of ammonia leaking from the shaft seal and onto the sensor had knocked it out of calibration. This is because the sensor needs to be calibrated to a zero ammonia atmosphere as a reference point.

The Repair

After changing the shaft seal, we decided to change all 4 of the sensors and plug the detection system into our laptop for calibration. The benchmark was set for each sensor, then each sensor was bump tested to the required parts per million of ammonia to ensure that the detector trips when it should. All read backs were found to be okay, so we completed the calibration certificate which the customer keeps in his chiller file.

Related Articles:
Industrial Refrigeration Oil

Industrial Refrigeration Ammonia

Industrial Refrigeration Sludge

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17/10/2021
Maximus Chillers
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Red chiller with lantern illuminating the internal components showing test equipment for checking chiller efficiency

Improve Chiller Efficiency

Category : Articles

In this article we will be looking at some basic ways to improve chiller efficiency...

News Article No.18

Improve Chiller Efficiency with a Clean Condenser

When an air cooled condenser becomes blocked, there is a reduction in air flow through it. This causes a high pressure condition to exist. The compressor pulls more amps to achieve the same mass flow rate of refrigerant. Also, more fans come on to try and reduce the excessive pressure. The on site maintenance team usually brush down the condensers at regular intervals. However, some of the contaminants require specialist cleaning equipment to be used by our engineers during the scheduled maintenance visits. We also carry a set of fin alignment tools to ensure that the air flow is kept at its optimum condition.

Improve Chiller Efficiency by Removing Evaporator Thermal Insulation

Contaminants circulating in the water system accumulate on the surface of the tubes in the evaporator. This thermal insulation prevents the absorption of latent heat into the chiller refrigerant system. Because the water is not being chilled efficiently, the compressor stays on longer to try to achieve set point. When this condition is allowed to deteriorate, the compressor never goes off and the chilled water temperature rises to a point where little effect is being made to the cooling of buildings or the cooling of an industrial process. We strip down the heat exchanger and use specialist cleaning equipment to repair the problem.

Blocked Strainer

This problem is particularly prevalent on chillers supplying chilled water to a heavy industrial process. The strainer is essential to prevent the contaminants continuing to the evaporator and causing the above mentioned thermal insulation. This is usually one of the periodic checks of the on site engineers as part of their planned preventative maintenance schedule. Our engineers also check the strainer on each maintenance visit.

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Improve Chiller Efficiency with Correct Refrigerant Charge

In the photo, the superheat and subcooling values are being worked out by one of our engineers. This is how we determine a refrigerant shortage. Less latent heat is being absorbed into the chiller refrigerant and so a lot of electricity is being used with little effect to the chilling of the water.

Refrigerant Leak Repairs

The remaining refrigerant is decanted from the system using a pump out unit and recovery cylinders. We then pressure leak test the entire system using nitrogen. After locating the leaks, we repair them using oxy-acetylene. The system is then pressure tested according to industry guidelines to ensure its integrity. Then, the dehydration process is carried out by pulling the system down to a near vacuum. This also has the effect of removing non condensables from the system, such as, air and nitrogen. We then recharge the system with refrigerant, a little at a time, until the superheat and subcooling readings come to within standard industry guidelines. This saves a considerable amount of electricity used for the running of the plant.

F-gas Register

Our leak tests and follow up leak tests are recorded in your F-gas register so that when an external auditor arrives on site, you can show that you are maintaining your plant according to the current regulations.

Blocked Pump Fan

On smaller process chillers, the water system pump is located inside the chiller. Over time, the pump cooling fan inlet becomes blocked causing a reduced air flow across the external cooling fins on the pump. This causes the pump to run hotter and so pulling more amps. The bearing life of the pump is also reduced because of its inefficient operation. As well as the increased cost of electricity, expensive pump replacement is needed at more frequent intervals. Pump efficiency and functionality checks are just some of the procedures that we carry out during a maintenance visit.

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Shell & Tube Chiller Evaporator Maintenance

Waste of Money

When you look at these examples of inefficiently running chillers, it is easy to see that there is a significant waste of electricity and the untimely replacement of parts. The above are just a few examples of some of the more basic reasons for a poorly running chiller.

Maintenance Visits Improve Chiller Efficiency

We carry out an extensive list of other checks and procedures during each maintenance visit. We have developed a detailed Tick Sheet to ensure that our engineers do not forget any of the adjustments that can be made.

Mobile Workshop

We also carry an extensive selection of commonly used parts and materials in each company car. This means that we can often improve a chiller’s performance during a visit with no extra cost.

Kilowatt Hour Meters

Our maintenance saves money! With new customers who have poorly maintained chillers, we have the option of fitting kilowatt hour meters. We record the amount of electricity being used at the start of the contract. Then, we carry out our list of procedures and adjustments to improve the running of your chillers. This is a visual way for our customers to see just how much money they are saving. When this is compared to the cost of a maintenance contract, they can see how worthwhile it is having Maximus Chillers on site.

Scheduled Chiller Maintenance

Send us an asset list of your chillers and we will put together a maintenance schedule to keep your chillers running in the best condition. We will recommend how many visits are required each year and what needs to take place on each visit. A plan will be put together regarding the procedures that your onsite engineers can carry out in between visits.

Technical Support Desk

To keep your costs down, we offer a free Technical Support Desk to all of our contract customers. Manuals and passwords can be sent in PDF format direct to your computer. To further assist, we offer real time technical support using face time on your phone. This is because it is often a lot easier to show our technical engineer a chiller that is running poorly, rather than to explain it.

Related Articles:
Air Cooled Chiller Condenser Testing

Planned Preventative Chiller Maintenance

Chiller Maintenance Service

Chiller Tube Cleaning Service

Chiller Condenser Tube Cleaning

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Read more about how to improve chiller efficiency on The Engineering Mindset

10/10/2021
Maximus Chillers
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Example of chiller types: 2 grey containerised ammonia chillers with air cooled condensers on top

Chiller System Types

Tags : air cooled chiller condensers chiller compressor systems chiller evaporators chiller expansion valves chiller refrigerant charging chiller refrigerant latent heat chiller refrigerant leaks r407c chiller refrigerant shell and tube chiller condensers

Category : Articles

In this article we will be exploring the various chiller system types. They can be categorised according to: how the condenser is cooled, weather they use vapour compression or absorption and the required chilled water temperature…

News Article No.17

Air Cooled Chiller System Types

This type of chiller uses the ambient air to cool the refrigerant in the condenser. Fans suck the air through the condenser fins and so exchanging heat energy from the refrigerant and into the air. They are particularly popular in the UK due to the low ambient temperatures. They are also used in the Middle East, but the higher ambient means that they run less efficiently. Read more about air cooled chillers

Water Cooled Chiller System Types

This type of chiller uses a shell and tube condenser to remove the heat energy from the refrigerant. The refrigerant condenses from a gas and into a liquid on one side of the tubes. On the other side of the tubes, condenser cooling water is being pumped through and so absorbing latent heat from the refrigerant. The water flows up to a cooling tower where it cascades down through trays and into the sump. In the opposite direction, air is blown up through the cooling tower and so creating the required heat exchange. The cooled condenser water is then pumped back to the chiller. This kind of system is more often used with large capacity chillers. Read more about water cooled chillers

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Vapour Compression

Vapour compression is the most popular kind of chiller. An electric motor drives a compressor. The refrigerant is then discharged into the condenser where the heat energy is rejected from the refrigerant as it cools down into a liquid. It goes through an expansion valve where it drops in pressure and temperature. Then, the refrigerant goes into the evaporator where it boils off absorbing latent heat from the water being chilled. The refrigerant is then sucked back into the compressor. This is called The Basic Refrigeration Cycle read about it in detail.

HFC Chillers

HFC chiller refrigerants, such as, R407c were developed to replace refrigerants which contained chlorine. This is because chlorine was found to have caused a hole in the ozone layer. The downside to HFC refrigerants is that they have a high Global Warming Potential. That is to say that when they find their way into the atmosphere due to refrigerant leaks, their heat trapping qualities add to the greenhouse effect.

Ammonia Chillers

The photo is of two ammonia chillers with air cooled condensers on top. A steel braided refrigerant charging hose can be seen coming into the foreground of the photo. This refrigerant has a zero global warming potential and so is environmentally friendly. The downside to this refrigerant is that it is highly toxic and corrosive. Therefore, special procedures, equipment and training is required to handle it. Read more about ammonia chillers

Propane Chillers

Propane didn’t really catch on in the UK due to the higher initial cost of the chiller. It is, however, popular on the continent in countries such as Italy. The downside to this refrigerant is that it is highly flammable. Intrinsically safe equipment is required to handle the refrigerant and so aiding with a spark free environment. Read more about propane chillers

Absorption Chillers

This kind of chiller uses a heat source rather than electricity to drive the cooling process. It employs a chemical reaction between two substances, such as, lithium bromide and water. Read about absorption chillers in detail. This type of chiller is a lot less efficient than vapour compression systems. The coefficient of performance is usually around 0.5, were as with a HFC chiller it is usually upwards of 4. Therefore, they are most often used where there is a surplus of waste heat being produced by a process, such as, in a power station.

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Industrial Refrigeration Ammonia

High Temperature Chiller System Types

Laser cutters use a chiller which operates with a high temperature set point of around 25°C. The laser head and the oscillator need to be cooled to a very close deadband of usually around 0.2°C. If there is a problem with the laser chiller, the controls shut the laser cuter down to prevent expensive failures from occurring.

Medium Temperature Chiller System Types

Most chillers operate at this temperature which is used for a variety of applications including…

The Cooling of Buildings

The chilled water set point is usually around 6°C. Large capacity chillers are used which supply chilled water to the building. A plant room is located near to the chillers where a pump discharges into the chillers. The water system pressure is maintained using a pressurisation unit. A different pump is used to supply fan coils around the building. The fans blow air across the chilled coils and so cooling the spaces in the building. This heat exchange warms the chilled water which returns back to the chillers.

The Plastics Industry

Two popular ways of forming plastic are by using: plastic extrusion moulding machines and plastic injection moulding machines. Plastic granules or powder is melted down and forced through a die or into a mould. Chilled water is then used to control the cooling of the newly formed plastic to below its freezing point. Small chillers are used next to each of the plastic forming machines. Alternatively, large, centralised chillers are used to provide chilled water to the whole factory.

Low Temperature Chiller System Types

Breweries are a good example of the use of low temperature chillers. The setpoint is often around -5°C with glycol being added into the water to prevent it from freezing. The water/ glycol solution is pumped around the jackets of stainless steel vats which are used to brew the beer. The fermentation process created by the yeast is temperature critical and so is controlled by the chilled water.

Related Articles:
Air Cooled Chiller Maintenance

Chiller Condensers

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25/07/2021
Maximus Chillers
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Two large air cooled chillers during condenser testing

Air Cooled Chiller Condenser Testing

Category : Articles

We at Maximus Chillers have recently carried out air cooled chiller condenser testing at a new 3 year maintenance contract in the North West. The last of 4 systems had gone down on the morning that we first attended site. 1.2 MW of cooling had been lost which resulted in the water system temperature rising to 31°C. These chillers are used to cool an office block, so we wanted to get some of the systems up and running as quickly as possible…

News Article No.16

Air Cooled Chiller Condenser 1 Testing

One of the systems was disabled due to a condenser fan failure. 1 of 5 fans was found to be seized and disconnected. Fan speeds have sufficient redundancy built in to allow for a high ambient and a partially blocked condenser. There was a high ambient condition, but the condenser was found to be clean. Therefore, our engineer decided to run test the system and monitor the condenser pressure…

Fan Speed Transformer

3 fan speeds available on this chiller- low, medium and high. The fan speeds are achieved using a transformer which makes a different voltage for each fan speed. This is quite a good way of controlling the condenser pressure, as all of the fans run smoothly together. The program looks at the condenser pressure using a transducer, then selects the required fan speed.

Medium Fan Speed

As expected, the chiller program selected the medium fan speed. This provided the required saturation pressure in the condenser and so adequately subcooling the refrigerant.

Compressor Protection

All of the system pressures and temperatures were nominal, so the compressor was protected. There was a good oil return and sufficient cooling to the suction housing from the refrigerant. This cooling ensured that the internal motor windings did not overheat.

Monitoring

Having got this system away- our engineer monitored the water system temperature which started to come down. More cooling was required, however, to get the water system temperature down to set point…

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Air Cooled Chiller Condenser 2 Testing

Another system had been the only system running for some time.

Blocked Condenser

Grass pollination had caused a covering of organic material to accumulate on the condenser. The increased head pressure had caused the high pressure switch to trip. This type of material was easy for our apprentice to remove, as it clumped together when brushed.

HP Reset

The high pressure switch was reset and the system was run tested. It did not trip again, but a high pressure condition still persisted in the condenser.

Chemical Clean

Therefore, our engineer decided to carry out a chemical clean. After the whole of the ‘v’ type condenser was cleaned- the pressure came down a little.

Non Condensables

This system stayed running, but in the high fan speed. On the upcoming maintenance visit, a refrigerant diagnosis will be carried out to assess whether there are non condensables in the system. If this is the case, a false reading of subcooling will be recorded, as the non condensables throw out the calculation.

Cool Building

With 2 systems now running, the water system got down to set point. Our customer was really happy as the situation had gone from: office workers walking out of the building- to a cool building before 10 o’ clock on the first day of the contract.

Air Cooled Chiller Condenser 3 Testing

The third system had been on pressure test for the past 2 months with the condenser valved off. There was still pressure in the system, but our engineer decided to confirm the pressure test for himself. He did this by leaving it on pressure while having a drive round the suppliers. Several hours later, the pressure had remained constant, so he was able to start the evacuation process. After this was completed, the system was recharged and run tested. Now there were 3 systems up and running.

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Air Cooled Chiller Condenser PRV Testing

The pressure relief valves on the condensers have recently been changed. Industry guidelines state that they should be tested or replaced every 5 years. There is no guarantee that the PRVs will re seal satisfactorily after they have been tested. Therefore, in practice they are usually replaced. We inspected the date of the replacement, the burst pressure, the associated certification and paperwork- all was found to be satisfactory.

Air Cooled Chiller Condenser 4 Testing

The fourth system has a leak on the condenser with some refrigerant remaining in the system. This refrigerant will need to be decanted on a subsequent visit using a pump out unit and a recovery cylinder.

F-gas Leak Testing

The entire system will be pressure leak tested to identify the location of all leaks. Then, the leaks will be repaired using oxy-acetylene. After this, the system will be pressure tested to ensure its integrity.

Dehydration

Then, the dehydration process will be carried out. The achievable pressure of the vacuum pump will be tested and recorded. Evacuation will be carried out until this recorded pressure is achieved. Our engineers are issued with a powerful 10 cfm vacuum pump to speed up this process. This system will then be recharged and its operation tested.

Air Cooled Chiller Condenser Testing and Calibration

One of many tests that we will carry out on the upcoming maintenance visit is condenser transducer calibration. Transducer readings are not linear, so care will be taken to achieve an accurate calibration. A password will be entered into the controller to gain access to the required menu. Then, each of the transducers will be adjusted. The result of this means that accurate diagnosis can be carried out and the correct subcooling readings can be recorded.

The above is just part of the service that we provide to you- the customer! Having the capability to do anything and to extend the life of your chillers is part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere.

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Chilling Plant Service

Tags : chiller compressor oil level chiller condenser fans chiller control panels chiller control systems chiller diagnosis chiller electrical faults chiller evaporators chiller fault finding chiller water system flow switches maximus advantage screw chiller compressors tighten chiller wiring

To read more about air cooled chiller condensers hit the Tag at the top of the page.

Read more about an electrical transformer on Wikipedia

06/06/2021
Maximus Chillers
-

Chiller Commissioning

Category : Articles

Chiller commissioning is carried out to resolve any issues and get a machine running with optimum efficiency. The first three days are the most important part of a chiller’s life. This is because a chiller will carry along with it any problems that were not resolved at the start.

News Article No.15

New Chiller Commissioning

We at Maximus Chillers are the approved supplier for various manufacturers as their first choice to commission their new chillers. This is because we have earned a reputation within our industry for the capability to do anything- this is just part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere.

Used Chiller Commissioning

Our customers are concerned with lowering their carbon footprint and reducing the environmental impact made by cooling systems. One of the ways they do this is by purchasing used chillers which still have 10 years of life in them. This means that there is a dramatic saving in the carbon emissions that would have been released during the manufacture of new chillers. Used chillers often come from factories that have been re located. They also come with a full service history.

Chiller Commissioning on Site

The chiller in the photo is about to have the commissioning process carried out. All that is left to do is for the onsite engineers to fit the Inlet and Outlet pipes to the evaporator. Then, fit the water system pumps and other water system components.

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Chiller Commissioning Day 1

A cup of coffee and a good look round before staring anything. There were still a few nuts, bolts and washers left lying around by the onsite engineers, so a good opportunity for some house husbandry. This done, our engineer switched the main power supply on to the chiller…

Flow Fail

The machine went immediately into the flow fail fault. Then, he powered up the chiller pump set and the process pumps that feed the factory. The flow fail alarm cleared- so that was the flow switch ticked on our detailed Commissioning Sheet.

Line Voltage

He then checked the 415v power supply to the chiller which gave a good read back and balanced phases. Then, he checked the volts, amps and rotation on the pumps which also gave a good read back.

Buffer Tank Level

The buffer tank auto fill sensors had been positioned incorrectly. He adjusted them to the correct level, the mains water auto fill started and the tank filled to its set level.

Water System Leak

A small leak was found in between the outlet pipe from the buffer tank and the inlet of the process water pump. Our engineer rang one of the onsite engineers who arrived to tighten the connection.

Tighten Wiring

There hadn’t been an opportunity to tighten the wiring for some time as this chiller had been in continuous production in another part of the factory. Each wire around the chiller was tightened including the panel, the fan decks and the motor terminals on the Bitzer screw compressors.

Chiller Commissioning Day 2

The application and set point were different for the process at the new location of the chiller. Therefore, the controller was interrogated using a password to access the parameters. The parameters were modified, one at a time, until they came in line with the customer’s requirements.

Remote Controller

A remote controller had been fitted in the factory near to where the process workers carry out their duties. This was so that they do not have to walk outside to monitor the running of the chiller when they are also monitoring the process. Simultaneous monitoring of chiller loading, faults and water temperature is needed, as well as the monitoring of the process temperatures and production rates. The production rate can be slowed down if the chiller is in a fault condition. This is so as to balance against the process chilled water temperature.

Display Fault

A fault was showing on the remote controller display that was not showing on the chiller controller. After following the diagnosis and consulting the wiring diagram, the fault was traced to three wires that had been connected in the wrong order- an easy fault to rectify.

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Chiller Commissioning Day 3

Having sorted out the above, it was time to run the chiller up in anger…
A time was selected for start up when maximum load was available from the factory. This was to ensure that the machine could cope and to show up any problems.

System 1

This system started at 25% capacity and loaded up through each stage until it reached 100%.

Oil Level

A low oil level was recorded on the oil sight glass. Therefore, our engineer carefully monitored the compressor amps, temperatures and pressures to see if the compressor was starting to leave its nominal operating conditions. Bitzer screws are a high quality and very robust compressor, so the readings stayed good until the oil level returned.

System 2

This system then started and loaded steadily to 100%. All of the chiller readings were taken and were found to be within standard industry guidelines.

Load Matched

As the chiller started to near the set point, both compressors started to unload to match the load. The load can vary according to what the process engineers are doing at the time, so proving the compressor loading was critical to the efficient running of the plant.

Scheduled Maintenance

With the Commissioning Sheet filed in the cabinet, the next scheduled maintenance visit was talked through with the customer. There are 3 minor visits and 1 major visit during the year. The major visit is scheduled to take place during the winter. This is because there is more time available to carry out the periodic oil and filter changes.

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To read more about chiller electrical faults hit the Tag at the top of the page.

21/04/2021
Maximus Chillers
-

F-gas Chiller Leak Testing

Tags : chiller diagnosis chiller expansion valves chiller nitrogen pressure tests chiller refrigerant leaks chiller refrigerant liquid pipes chiller refrigerant subcooling chiller refrigerant superheat chiller refrigerant system pressure testing f-gas chiller leak testing procedure low chiller refrigerant charge r134a chiller refrigerant r407c chiller refrigerant r410a chiller refrigerant

Category : Articles

Regulations

The regulations for F-gas chiller leak testing have been devised to reduce the environmental impact of HFC refrigerants. They are standardised regulations which are implemented across Europe. Now that we have left the EU, we will continue to be aligned with these regulations.

News Article No.14

Leak Test Frequency Required

The frequency of leak tests depends on the type and quantity of the refrigerant. For example, a system which runs on R134a, the frequency is:
• once every 12 months for a charge less than 3.5 kg.
• once every 6 months for a charge less than 35 kg.
• once every 3 months for a charge less than 350 kg.
All of our maintenance schedules far exceed these minimum requirements. This is because our customers require maintenance visits more often to ensure the efficient running of their plant.

Static Leak Detectors

These leak detectors must be fitted to systems with more than 500 tonnes of CO2 equivalent. For the refrigerants most commonly used in chillers this is:
• R410a 239 kg
• R407c 282 kg
• R134a 350 kg

Global Warming Potential

The GWP numbers below represent the amount of greenhouse effect each refrigerant has, by comparison with an equal mass of carbon dioxide:
• R410a 2,088
• R407c 1,732
• R134a 1,300

Now we have had a look at some of the regulations, let’s have a look at a day in the life of our engineers here at Maximus Chillers. Read below for three different examples of leak testing carried out in the field…

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Pressure Testing following a Leak

In the photo a leak has just been brazed on the condenser. It is recommended in the industry to use a steel braided line with a ¼ turn valve. This is so that if a nitrogen regulator malfunctions, it can be valved off, instead of a system being filled with bottle pressure from the cylinder. For a small system, this could cause a catastrophic explosion. We decided, therefore, to use a small cylinder which would expand into the large volume of the chiller. Should this fault occur, the safe working pressure would not be exceeded. This was taken into account when writing our Risk Assessment Method Statement. The pressure was built up in stages until the test pressure was achieved. This was recorded on our Pressure Test Certificate and witnessed by the customer. The result of the pressure test 4 hrs later was satisfactory and also witnessed by the customer.

Follow up Actions

A return visit was arranged 2 weeks later to leak test the chiller again. Our engineer carried out a visual inspection of all of the parts of the refrigerant pipework. He then used an electronic leak detector to see if it went into alarm. All was okay, so he completed the F-gas Certificate and left it in the customer’s file.

Routine F-gas Chiller Leak Testing during Maintenance

On another site, we look after 6 air cooled MW chillers in a row outside a building at a petrochemical facility. Our engineer ran the systems up, one at a time, to 100% so as to show up any refrigerant shortages. He was looking at the subcooling and superheat values. Two of the systems had poor readings which alerted his attention to a potential leak. On one of the systems, the poor readings were found to be caused by a faulty expansion valve. On the other, he diagnosed that the chiller was running short of refrigerant. He then carried out an inspection and found signs of a leak on a liquid pipe, just after the filter/ drier. The system was locked off with the refrigerant valves closed either side of the leak. This was to prevent the refrigerant from carrying on leaking to atmosphere. Then, he sent a report into Head Office detailing the estimated refrigerant addition needed to replace the refrigerant lost. Refrigerant removal was not needed as the area of the leak had been valved off from the rest of the system. He also detailed the materials required for the job and the necessary labour time that would be needed.

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Looking for a Leak

There are a variety of methods that can be used to identify the location of a refrigerant leak. Here are some examples…

Ultrasonic F-gas Chiller Leak Testing

An ultrasonic leak detector uses a microphone on the end of a wand. This is connected to a battery and processing pack, which is where headphones are plugged into. The sensitivity can be adjusted on the processing pack until a good working level is found. The various components on the chiller can then be inspected to find an audible sound of a leak.

Electronic F-gas Chiller Leak Testing

Otherwise known as a sniff tester, the electronic leak detector is one of the most popular types of leak detectors. The battery can be recharged via the cigar lighter in a car, or can be recharged back at the office with a transformer plugged into the mains. The heated diode sensor and the filter can fail or need to be replaced, so replacement parts are available. The instrument needs to be calibrated to a no refrigerant atmosphere, then it takes samples of the atmosphere being tested. It compares the two atmospheres and looks for a difference. Most electronic leak detectors work with all HFC refrigerants.

Bubble Up F-gas Chiller Leak Testing

There are a variety of bubble up leak detection sprays that are available off the shelf. At Maximus Chillers we make our own leak detection solution in our laboratory at Head Office. We mix two chemicals together in the correct proportions. This solution is carried in sprayer bottles in the boot of each of our company vehicles. When looking for a leak, our engineers use it around the suspected areas of a leak. It is the best form of leak detection that we know, as it can find the smallest of leaks, right up to large leaks which are audible to the ear.

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To read more about the f-gas chiller leak testing procedure hit the Tag at the top of the page.

Read more about checking F-gas equipment for leaks on the Government website

28/03/2021
Maximus Chillers
-

Chiller Fault Finding & Diagnosis

Tags : chiller condenser high pressure switches chiller control panels chiller diagnosis chiller evaporator low pressure switches chiller fault finding chiller refrigerant pressure temperature relationship chiller refrigerant subcooling chiller refrigerant superheat chiller relay boards chiller water system flow switches maximus advantage

Category : Articles

Accurate chiller fault finding & diagnosis saves money! This is because when the wrong parts are ordered and your machine still does not work- it has been a wasted visit with unneeded parts.

News Article No.12

Expert Training for Chiller Fault Finding & Diagnosis

All of our engineers are time served, attending the Government approved college course. This includes the F-gas HFC and BESA ammonia refrigerant handling certificates. Our engineers also go through rigorous training at The Maximus School of Chillers at Head Office in Droylsden. Here we have various chiller types ranging from small air cooled chillers, to the panels for large water cooled, screw and centrifugal chillers. They have been wired up as test rigs to simulate the various fault conditions. The manager will simulate a fault and the engineer will then have to follow it through to a successful diagnosis. This off site training ensures that when our engineer attends site, he is armed with all the skills he needs to follow through the fault finding easily.

Technical Support Desk

Whilst on site, our engineer is connected to our live stream, real time Technical Support Desk on his laptop and smart phone. He can also face time the support desk on his device. We often find that it is a lot easier to show somebody something than describe it. This service is available to you the customer too- free of charge. It is just one of the many features that help us to achieve The MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. PDF chiller manuals and wiring diagrams can be sent to our engineer’s phone and then printed off on your computer. This means that you have all the technical information you need, in the chiller panel for when our engineer is not in attendance. Just face time our support desk and we will talk you through. This helps to keep your service costs down as it will often save you the cost of a call out.

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Mobile Workshop for Chiller Fault Finding & Diagnosis

Each car boot is a mobile workshop with a blueprint of equipment repeated across each car in our fleet. We have recently opened The Spanish Office with one engineer down there now too. Our fleet of cars in the UK are Peugeot 508 and in Spain our engineer has a Seat Arona. In both countries the equipment is duplicated and standardised. This is so that Head Office knows what each engineer has at his disposal while on site, so he can find out what the problem is- fast!

Fuse Wire

It is the small things that we carry that help- fuse wire for example. This is so that a big box of spare fuses does not have to be carried.

Contactors

We carry 4 medium sized contactors which have 24vac, 24vdc, 110v and 230v coils. Each has NO (normally open) and NC (normally closed) contacts. This means that a blown relay, or a process chiller compressor single phasing- will be repaired while on site. Just another cost saving exercise for you the customer.

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Fluke Multi Meters

Our multi meters are calibrated annually for accuracy. They are equipped with fused leads to protect the engineer when working on high voltages. They have long, thin prongs too for access to the most difficult locations. Electrical plugs which are fixed onto relay boards are a good example. We test:

Resistance Temperature Detectors

RTDs are sensors that are often: NTC (negative temperature coefficient) where the resistance drops when warmed. PTC (positive temperature coefficient) where the resistance goes up when warmed. The sensor reacts to temperature in a predictable way, so a chart can be composed by the manufacturer. This chart shows the resistance reading, which should correspond to a given temperature. When a resistance reading on the multi meter is not where it should be on the chart- the sensor has failed. We carry crocodile clips for our multi meter prongs because sensor wires can be difficult to hold against our standard prongs.

DC Chiller Fault Finding & Diagnosis

We mostly fault find the direct current which is associated with the controls of a chiller. DC is also found in inverter drives before it is re inverted back into AC on the compressor. We usually fault find inverter drives on either end, however, when the volts are AC. PCB electronics usually run on 5vdc as computer components work well with this kind of voltage. That is not to say that there is not 24v and 230v present on a PCB, it may be part of other things that the PCB is doing. We have the function to read DC on our multi meters.

AC Chiller Fault Finding & Diagnosis

The most often used function on our multi meters is AC. This is because most components around a chiller panel are usually AC. The safety chain including the low pressure, high pressure and flow switches are usually fed by a 230v supply. The 415v line volts to fans, pumps compressors etc. are AC too. On large air cooled chillers, the panel is quite big to control all of the components and devices around the chiller. On large screw and centrifugal chillers, it is just a small panel with the compressor starter panel usually being separate.

Fridge System

Our calibrated gauges can be fitted to a HFC or ammonia chiller with a selection of fittings for each machine type. We carry digital thermometers with various probe types to access the different parts of the machine. Usually, however, the pressures and temperatures are available on the chiller controller. We use these pressures and temperatures, along with a comparator app to diagnose the condition of the fridge system. Superheat and subcooling values are worked out which are transmitted, real time, to our technical support desk. This means, along with the data plate of the chiller which is stored in our system, we can provide you with a Quote for the service job while the engineer is still on site.

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Tags : air cooled chiller condensers chiller compressor systems chiller condenser high pressure control chiller condenser high pressure faults chiller condenser high pressure switches chiller control systems chiller electrical faults chiller expansion valves chiller liquid line solenoid valves chiller nitrogen pressure tests chiller pipework oxy-acetylene brazing chiller refrigerant discharge pipes chiller refrigerant economizers chiller refrigerant high pressure gauges chiller refrigerant latent heat chiller refrigerant leaks chiller refrigerant saturation chiller refrigerant subcooling chiller refrigerant suction pipes chiller refrigerant superheat chiller refrigerant system vacuum pumps chiller refrigerant system vibration eliminators chiller refrigerant torr gauges f-gas chiller leak testing procedure leaking chiller condensers low refrigerant pressure faults plate chiller evaporators scroll chiller compressors shell and tube chiller evaporators

To read more about chiller diagnosis and chiller fault finding hit the Tags at the top of the page.

31/01/2021
Maximus Chillers
-

Chiller Service Company Visit

Category : Articles

A typical rainy day in the North West, perfect for a chiller service company visit.

News Article No.11

Electrical Faults during Chiller Service Company Visit

This was a return visit to do a refrigerant leak, but the customer alerted our engineer’s attention to an electrical fault. System 2 was found to be locked out in fault on the recent maintenance visit, but now System 1 was being held off too. The fault message on the controller was High Pressure. The controller sends a 240v fault feedback signal, through the high pressure switch which returns to the controller. Our engineer had a look at the wiring diagram to find the number on the terminal strip and checked it out with his multimeter. As he suspected, there were volts going out, but not coming back. He removed the side panel for system 1 and found the switch on the discharge pipe. It was the type that has a red button on the top. When he pressed it, there was a click and volts returned to the controller.

Alarm Reset during Chiller Company Service Visit

He interrogated the Carel controller and followed the reset procedure. The controls went through a timer and then the start sequence was initiated.

Run Testing during Chiller Company Service Visit

After the first scroll compressor started, the head pressure started to build up, but the condenser fans did not start. The on board high pressure gauge carried on rising until the high pressure switch was tripped again.

Head Pressure Control

A transducer on the discharge is used by the controller to sense the pressure in the condenser. When our engineer looked for this in the controller, it was found to be reading wrong by a considerable amount. There is a facility to enter a password and recalibrate the transducer, but this only allows for a small adjustment.

Test Instrument

Our engineers carry various kinds of test instruments which can be used to give a temporary false reading to the controller. This gets the customer up and running and back in production whilst a new transducer is ordered and sent to site.

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Chiller Company Service Low Pressure Visit

Now on with the job to resolve the low pressure issue with the chiller.

Refrigerant Pump Out

Our engineer lifted the liquid line solenoid valve and decanted the remaining refrigerant into a vessel using his recovery unit. He only got out 7kg of a charge of 36kg.

Leak Testing during Chiller Company Service Visit

We use nitrogen for the leak testing as it is an inert gas that will not cause problems with the refrigerant system. There was a sign of the leak in between the steel frame at the middle of the condenser and the condenser tubes. We always strip the chiller down and leak test the entire system though. This is so that the job does not end up going round in circles. At first the leak could not be found, so the pressure was built up in stages, taking into account industry recommended guidelines for a chiller. Sure enough the leak was where it was suspected to be. The occurrence of this kind of leak can be reduced with the use of vibration eliminators.

Brazing during Chiller Company Service Visit

The location of the leak was reported to the maintenance engineer onsite and a hot work permit obtained. The equipment we use is tested at regular intervals to be safe and in good working order. A half hour fire watch was stipulated in the permit, along with the removal of combustible materials from the work location. Correct PPE being donned, he brazed the leak to the required industry standards.

F-gas Pressure Test

A chiller has a different pressure test procedure to other systems, so our engineer built the pressure up according to industry standards, then recorded it on his pressure test certificate. After the required time had elapsed, he rechecked the readings which were found to be satisfactory.

Vac Pump

Each of our engineers carries a state of the art 10 cfm vacuum pump to speed up the dehydration process. We use high quality Torr gauges too, so as to get an accurate pressure reading. A good read back was achieved at the end of the process.

Recharge and Run Test

After the refrigerant recharge was carried out, a satisfactory run test was achieved.

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Refrigerant Economizers

This particular chiller uses an economizer to further subcool the refrigerant. Chiller designers have worked out that the end user can save a considerable amount of money over 10 years if these components are used. After the subcooled liquid refrigerant leaves the condenser, it goes through a plate heat exchanger. Some of this refrigerant, however, is diverted through a thermostatic expansion valve, to the other side of this plate heat exchanger. Further subcooling occurring through the plates.

Expansion Valve

The refrigerant drops in pressure as it goes through the expansion valve. A bulb is fitted to the suction pipe on the outlet of the heat exchanger. The bulb has to be at the correct 'o clock position as oil insulation will affect the operation of the valve. A capillary tube connects the bulb to the valve. Inside the bulb, the same kind of refrigerant that is running in the system is present in its liquid state. As the temperature rises in the suction pipe, this refrigerant boils off, adding pressure into the capillary tube. This added pressure forces the power element down on the valve body and a needle forces the valve open.

Flash Gas

Imagine if the refrigerant was not subcooled at all. It would be around its saturation point with a lot of it flashing off into its vapour phase. Not good when you have warm water coming back from the process. The refrigerant would not absorb very much latent heat into the refrigerant system.

Efficiency

Imagine, on the other hand, the economizer which is fitted to this chiller. Now we have a good proportion of refrigerant in its liquid phase, on the low side of the system, with a minimum amount of flash gas. The warm process water has more chance to cool and the refrigerant absorbs a lot more latent heat. The chiller achieves set point easier and therefore saves a considerable amount of electricity. With this further subcooling monitored for a while, time for a signature from the customer and another job well done!

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Tags : centrifugal chiller compressors chiller compressor loading solenoid coils chiller compressor loading solenoid valves chiller compressor slide valves chiller compressor systems chiller control systems chiller fault finding chiller refrigerant economizers chiller refrigerant low pressure gauges chiller refrigerant mass flow rate chiller refrigerant pressure temperature relationship chiller refrigerant saturation chiller refrigerant standing pressure reciprocating chiller compressors screw chiller compressors screw compressor slide valve potentiometers

Chiller Problems

To read more about chiller electrical faults hit the Tag at the top of the page.

Read more about F-gas leak checking at Refcom

31/12/2020
Maximus Chillers
-

Industrial Chiller Service

Category : Articles

On an industrial chiller service visit, the ammonia alarm was found to have been triggered.

News Article No.10

Industrial Chiller Service Faults

The onsite engineer had fault found the chiller and silenced the alarm, the yellow light was still flashing. The red light was lit on the panel and the red LED was illuminated on the ammonia alarm console. He had reported a smell of ammonia to us over the phone. This gave us a priority of getting to site, as many other alarms of this nature are often spurious. Our engineer attended site within an hour and confirmed that the fault finding was correct as described by the onsite engineer. The chiller is containerized in design as it is situated outside. All around the chiller are door panels for access to the various system components.

Breathing Apparatus and PPE

He donned his mask and full length ammonia resistant PPE before opening one of the panel doors. This was to ensure that he did not get overwhelmed by the refrigerant when he opened the door. He started with the door into the storage area of the containerized chiller. A strong blast of ammonia came out in his face- lucky for the PPE!

Localising the Fault

Working his way around the chiller, our engineer found more and more hazardous door openings! Eventually he found the culprit: one of the two flanges were leaking on the oil return solenoid. The refrigerant vapour was coming out in its usual white form. The oil return pipe feeds off the oil pot which is a chamber that the oil sinks into from the refrigerant economizer. This vessel was valved off and the other end of the pipe valved off too.

Pinpointing the Fault

Now that the ammonia refrigerant leak had started to calm down- it was possible to see through the white vapour to exactly which of the flanges was leaking. It was the right one as seen in the picture. It consists of an ‘o’ ring made of ammonia resistant rubber material.

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Industrial Chiller Service in Local

The above mentioned chiller runs in local in a lead/ lag configuration with the adjacent chiller. That is to say- there is no wire or modem to a remote location. A panel is available in between the two chillers to sequence the switch over between the two. When the chiller tripped out due to the fault, the other chiller was supposed to have been enabled. This did not happen, so our engineer investigated the situation. The sequencer panel sends out a 24v fault feedback signal to each chiller. This, in turn, goes through a relay and back to the sequencer panel if all is good. When a fault occurs, the volts drop out to the relay in the chiller and a relay drops out in the sequencer. When the relay drops out in the sequencer, a normally closed contact makes and brings a red light on. This was not happening, so our engineer followed it through with his multimeter. He found a blown 1 Amp control fuse in the chiller, he replaced it and it blew again. After some careful research he found that there was an earth leakage due to the ingress of water into a safety switch. This switch was nothing to do with the above, but it blew the whole control circuit. Having reinstated the fuse, he found that the panel switched over satisfactorily in local.

Advantages

This kind of operation method has an advantage in its simplicity. There are no complicated BMS systems for the chiller to be integrated into. A sequencer panel is easy to construct and maintain- keeping the costs down to the end user.

Disadvantages

The disadvantage of this kind of system is that the first thing the factory usually notices is that they are loosing the process. The water temperature getting too high is the first alarm signal. With this site, however, there is a permanent onsite engineer on hand. He is experienced with the first checks to carry out and can often get the plant running with no problem.

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Standing Pressure during Industrial Chiller Service

The standing pressure was taken into account on the return visit to fit the oil return solenoid valve seal. Because the valve is on the low side of the system, when the chiller is off, the pressure is higher than when it is on. Therefore, so long as the seal pressure tests to this pressure, then all will be good when the system is running. That is assuming that the valve seals work satisfactorily at a lower temperature range. There are issues sometimes when a seal will be okay at ambient temperature but will leak when it becomes brittle at a colder temperature. This happens usually on an old seal and, indeed, this condition can be tested for when run testing the system.

Leak Testing during Industrial Chiller Service

On fitting the seal, our engineer donned full length ammonia resistant PPE and breathing apparatus. A little at a time, he introduced refrigerant into the area of the valve seal. Any residual air being purged through a valve.

Pressure and Temperature

The standing pressure of refrigerant is affected by temperature. That is to say- that the higher the temperature- the higher the pressure. On the day this job was carried out, the ambient temperature was 12°C and using an app on his phone, he calculated that the pressure should be 5.6bar. This is consistent with Charles’ Law of Constant Volume with a coefficient added for this particular refrigerant. If the pressure had been higher than this, it would indicate the presence of air in the system. Daltons’ Law of Partial Pressures states that all gasses in a vessel will act as if they are on their own, therefore, causing a higher pressure.

Run Testing during Industrial Chiller Service

After the pressure was built up to full standing pressure and the seal held satisfactorily, the system was then run tested to ensure, as stated above, that the seal performed well across the full temperature range during the operation of the plant.

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Mass Flow Rate during Industrial Chiller Service

The mass of refrigerant passing, which is measured by the second.

Suction Density

In this case of the oil return valve seal, we are looking at the density of the low side refrigerant as it passes into the suction port of the compressor. This is shown on the LP gauge near to the compressor. The higher the pressure of the refrigerant, the more refrigerant there is- so it has a higher mass flow rate. This system has a refrigerant saturation point of 1°C which corresponds to a pressure 3.4bar. That is a high mass flow rate for this kind of refrigerant. This is because this refrigerant is usually used in low temperature applications where the pressure of the refrigerant is below that of the atmosphere. In that condition, when a leak occurs on the low side of the system- air leaks in. Air bleed valves are available to remove this unwanted air from the system.

Compressor Loading

The bigger the compressor on a chiller- the higher the mass flow rate. Most compressors have loading solenoids, vanes, or a slide valve to regulate this.

Piston Displacement

Reciprocating compressors use loading solenoids to increase piston displacement. Usually, oil from the oil pump holds the piston valves open and so preventing compression on that cylinder. When more flow rate is needed- the loading solenoid de energizes- the piston valves drop and the cylinder comes into action. Therefore, increasing the mass of refrigerant through the compressor.

Vanes

Vanes are used on centrifugal compressors to increase the flow of refrigerant through the compressor. An actuator linked to a chain is used to open the vanes. The controls work out the correct position of the vanes for a given load condition.

Slide Valve

The slide valve offers a seamless amount of loading, anywhere between 0% and 100% A slide valve potentiometer senses the position of the slide so that the controls can regulate the flow through the compressor. The screw compressor in this article uses a slide valve- on full load with the slide at 100% all readings were taken with a good read back. Another job done- another happy customer!

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21/11/2020
Maximus Chillers
-

Preventative Chiller Maintenance

We at Maximus Chillers will optimise the efficiency and take years off the life of your plant with preventative chiller maintenance.

News Article No.9

Control Panels

The first thing our engineers check at the start of the maintenance is the control panel of the chiller. In here he checks:

Programmable Logic Controller

Alarm History

The alarm history is analysed in sequential order to build up a picture of the last maintenance period.

Settings and Timers

The various levels of password accessed menus are checked and adjusted for efficiency and to eliminate any spurious trips on the running of the chiller.

Compressor Run Hours

We make a note of the compressor run hours on our detailed Tick Sheet. Bearings on centrifugal compressors and valve gear on reciprocating compressors are changed at pre prescribed intervals as defined by the manufacturer. This is to prevent an expensive failure and the resulting remanufacturing of the compressor.

Preventative Chiller Maintenance of Electrical Safety Devices

Fuses

Each one of these is popped from its holder and the continuity checked with a multimeter. This is maintenance the right way round, instead of run testing and following the fault back to the fuse.

Circuit Breakers

Each of the breakers is tested to ensure it will function correctly when it needs to.

Residual Current Device

RCDs work by detecting current leakage to earth. It monitors the difference between the live and neutral poles. As above these are tested on each visit.

Preventative Chiller Maintenance of Refrigerant Safety Switches

High Pressure Switches

The settings and dead band (the difference in pressure between cut out and cut in) are checked and adjusted on each visit. Sometimes due to malfunctioning controls or condenser condition, fans can be manually left off or can be forced on. Not the best running condition, but we will keep you up and running until we send out the new parts. Where this is a bespoke manufactured condenser, we have the best lead time available.

Low Pressure Switches

As above, the low pressure switches are checked and adjusted as need be. The seasonal and varying load conditions affect the saturation point of the refrigerant in the evaporator. This can cause untimely trip outs when the plant is otherwise running in optimum efficiency.

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Coefficient of Performance during Preventative Chiller Maintenance

The coefficient of performance is the cooling effect compared with the electrical energy supplied to the chiller. It is represented in a ratio, for example 6:1. That is six times more cooling effect compared with the electricity supplied. The higher the cooling effect relative to electricity supplied, the lower the cost in electricity. The ratio is often divided by 1 to show as just a number- in this example 6. The cooling effect is measured in kj/kg and the electrical supply is represented in kw/h.

Latent Heat

A chiller system would have a COP of less than 1 if not for latent heat. Exploiting this hidden heat when both evaporating and condensing the refrigerant is one of the founding principles of the basic refrigeration cycle. It takes a lot of heat added to the system to get the refrigerant to boil, then the same amount of heat is rejected from the condenser in the liquification of the refrigerant.

System Efficiency

A lot of basic things routinely drag down the efficiency of a chiller system. Just with the effect of our engineer attending site to carry out the maintenance- he will keep the COP optimised. Here are some of the system checks and procedures he carries out:

Superheat

When a compressor never goes off due to refrigerant shortage, there is a dramatic increase in electricity consumption. Also, the system will not have very much cooling effect. Continuing like this will cost more money and achieve little.

Subcooling

Basic condenser maintenance will improve the subcooling values. These readings will be taken at various load and ambient conditions at different times of the year. This is so we can build up an understanding of the plant. We carry a wide range of chemicals for the maintenance of your condenser. These chemicals are carefully selected so that they do not damage the condenser causing leaks. Condenser fans also cause a poor COP:

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Preventative Chiller Maintenance and Condenser Fans

Basic Design

With some basic chiller designs, the chiller condenser fans come on and off forwards and backwards at different pressures. This means that when other fans have failed, or are stuck going backwards- the one on the end comes on with the higher pressure then blows to earth. This is due to the ingress of water in the year it did not run.

Refrigerant Leaks

The above design means that there are fluctuating pressures in the condenser. This causes continuous expanding and contracting of the copper tubes. These copper tubes rub against the steel frame which is holding them in place- causing reoccurring leaks. Another reason for repeated leaks on the condenser is the vibration issue of the fans banging on and off. Add into this equation a cheap, flimsy frame that develops its own resonance- you then have an un ending problem.

Preventative Chiller Maintenance with Fan Speed Controllers

Part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere is that we can source any fan speed controller from our fast supply chain. This remedies the problem, as fan speed controllers bring all the fans on together at different speeds. Therefore, extending the lifespan of the fan and maintaining an efficient coefficient of performance.

Axial Fans

Most air cooled chillers use axial fans. They suck the air through the condenser and reject it upwards and away from the chiller. Ducts are often fitted to help this process. Scaffolding is erected to provide safe access to engineers.

Radial Fans

Radial fans are also called centrifugal fans or blowers. They are very popular in server rooms where air is blown down into a mezzanine floor and up through the racks. They are also used outside in chillers where they blow out and away from the chiller. They are usually driven by belts which require regular inspection and maintenance.

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Preventative Chiller Maintenance and R134a Refrigerant

In the photo, the controller shows R134a refrigerant and the 8.3°C of superheat as calculated by the program. This superheat may look at first to be okay, but when considering the compressor loading and expansion valve- it points towards a system issue. Our engineers diagnose if the issue is related to a component or a refrigerant shortage.

Characteristics

HFC refrigerant which has a chemical name of Tetrafluoroethane or CF3CH2F. It has low toxicity which is good for the health and safety or our engineers. It is not combustible, but other chemicals are made as a result of a fire. It is non corrosive too, which extends the lifespan of the pipework and components around the system.

Centrifugal Drop In

This refrigerant is widely used as a replacement for HCFCs, such as, R22 used in centrifugal chillers. It is only one fluid, where as the other popular HFC refrigerants are blends. These blends fractionalize in a flooded condenser or evaporator. That is to say: one or two of the refrigerants in the blend separate out and do not continue their cycle around the system. The chiller now has the wrong refrigerant circulating around the system for the application temperature. Extreme running faults follow, such as, ice on the compressor, suction pipe and expansion pipe. This is as a result of the refrigerant pressures and temperatures being outside of nominal conditions.

Global Warming Potential

A global warming potential of 1430 is considered to be high. Therefore, the refrigerant is being phased down to 21% by 2030 in line with F-gas guidelines. These guidelines are in accordance with the European Union and the Kyoto Protocol. Because of the regulations for the handling of fluorinated gas, our engineers attend college to learn how to decant the refrigerant safely. We then ship it to the recycling centre for disposal. A waste carrier note being completed each time to track the refrigerant from dispatch to disposal. Finally, F-gas leak tests are carried out and recorded on each visit. Maximus Chillers completes the picture.

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01/11/2020
Maximus Chillers
-

Chiller Breakdown

Tags : chiller condenser fan speed controllers chiller condenser fans chiller diagnosis chiller electrical faults chiller expansion valves chiller fault finding chiller nitrogen pressure tests chiller refrigerant leaks chiller refrigerant pressure temperature relationship chiller refrigerant subcooling chiller refrigerant system evacuation process chiller refrigerant system vacuum pumps chiller refrigerant torr gauges chiller run testing chiller water system flow switches f-gas chiller leak testing procedure low chiller refrigerant charge maximus advantage refrigerant system dehydration process

Category : Articles

A rainy day for a chiller breakdown for our engineer in the North West.

News Article No.8

Electrical Faults during Chiller Breakdown

Our customer called us out because he was having electrical faults with the chiller. The power supply to part of the panel had gone down and he required our assistance. Our engineer found a blown fuse which he replaced and tested operation- it blew again. Using his multimeter, he followed the diagnosis though to an earth fault on the flow switch…

Water System Flow Switches

The flow switch vapour seal had failed allowing rain water to ingress. This caused an earth failure on the 240v control circuit, and so blowing the fuse. The customer raised an order forthwith and so our engineer replaced the flow switch with the stock from his car. Each of our engineers keeps a range of flow switches for a variety of applications…

Stainless Steel

Where water system chemicals are corrosive, we carry corrosion resistant flow switches. This type has a longer working life due to the use of stainless steel. They are more expensive due to the higher manufacturing costs, but they are worth the money as they are less likely to fail, causing a potential loss of production.

Outside Use

This was the type fitted by our engineer on site in this news article. It has been developed and tested across a range of adverse weather conditions including freezing conditions and heavy rain. The electrical and switching compartment is protected by a sealing gland to keep the weather out. A rubber ‘o’ ring provides the seal into this compartment.

Inside Use

Some applications have the flow switch located inside the building in the plant room with the control cable extending out to the chiller controls. Another configuration allows for the flow switch to trip out the building controls and so dropping out the run signal to the chiller. In either case there is no need for weather proofing. This kind of flow switch is cheaper due to the lower construction costs.

High Pressure

Some water systems operate at considerable pressure. Therefore, high pressure flow switches have been developed for this application. They are capable of preventing water ingressing from the water system and into the electrical and switching compartment.

Test and Adjustment

Our engineer carried out testing and adjustments to the flow switch to ensure that it ran reliably. He achieved this by monitoring the water system readings and measurements against the design specifications of the switch. When he got it to settle down, he replaced the fuse and ran tested the chiller...

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Condenser Fans

The condenser fans were not coming on at all at first and later only slowly. They are controlled by a fan speed controller which is sensitive to pressure. A minimum value of volts is supplied to the fans, so as to prevent stalling and over heating of the internal motor windings. The fans were found to be in good working order, so he decided to turn his attention to…

Pressure Temperature Relationship of Refrigerant

There was found to be a lower pressure and so a lower temperature in the condenser. After careful fault finding and diagnosis involving putting the pressures and temperatures into a calculator, our engineer decided that the chiller was running short of refrigerant. This is consistent with Charles’s Law of Constant Volume. It is one of the fundamental scientific principals of how a chiller works: the higher the pressure- the higher the temperature/ the lower the pressure- the lower the temperature.

Recovery Units for Refrigerant

After receiving a further order from our customer, we gave the go ahead to our engineer to use his recovery unit to decant the gas. The refrigerant is sucked into the unit using a small one cylinder reciprocating compressor. The compressor discharges into the on board condenser which is cooled by a fan. The subcooled refrigerant travels down a refrigerant hose which is connected to the recovery cylinder in the picture. After this process was complete, he started looking for a leak...

Leak Testing and Pressure Testing

The leak was identified on the flange for the expansion valve. This component was removed, cleaned with our in house refrigerant grade solvent, then the joint re made with a compound suitable for the temperature range of the component. After a satisfactory nitrogen pressure test, the evacuation process can begin…

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Refrigerant System Vac Pumps

Each of our engineers carry a high capacity vacuum pump of the highest quality. We believe in investing in state of the art equipment as this is part of how we provide the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. Good equipment makes the job go easy.

Vane Pump

The pump works by sucking vapour into the inlet port. A rotary vane system extracts the vapour and discharges it through the top of the pump module. Oil is used to lubricate the vanes that slide around the pump cylinder. The vanes are kept a tight fit against the cylinder with the use of springs. As our pumps are high capacity, an oil filter is fitted to the outlet with a gauze inside to catch any oil droplets.

Electric Motor

This motor fits onto the back of the vane pump module. It comes from the factory set to 240v, but we change the pins for the electrical connections to convert it for use with 110v. This is because customers and engineers demand the use of 110v as if is safer for use in the UK climate. The 110v plugs and extension cable are shrouded and weather resistant. Weather resistant does not mean weatherproof, so we take measures to limit the exposure to adverse weather conditions. The pump motor, however, is not weather resistant at all, so care is taken to locate it somewhere dry. After a long time running, the motor runs hot, so our engineers take readings and carry out adjustments to ensure that it stays within its nominal operating temperature range.

Oil Changes during Chiller Breakdown

The vac pump oil is changed before each use with our specialist grade, high quality oil. Contact our office for prices and delivery times. The manufacturer of the pump recommends these oil changes as moisture and impurities absorb into the oil and so reduce its performance, also the working like of the pump.

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Refrigerant System Evacuation

Having set up the vacuum pump, our engineer started the evacuation process.

Torr Gauges used during Chiller Breakdown

We use analogue Torr gauges as they are more reliable than digital ones. Also, they do not need batteries and it does not matter if they get wet. Our engineer attached the Torr gauge to a suitable part of the system with a refrigerant hose, ensuring that a good seal was made between the components with a sealing compound.

Fittings used during Chiller Breakdown

Fittings were used to get between the different thread types from the vac pump to the fridge system. Having warmed up the pump for half an hour he was ready to start the process.

Non Condensables Removed during Chiller Breakdown

One purpose of evacuation is to remove the gasses that will not condense such as nitrogen remaining in the system from pressure testing. Another non condensable is air that has entered the system from when the expansion valve was removed. These non condensables affect how a fridge system works according to Dalton’s Law of Partial Pressures: that all gasses in a vessel act as if they are on their own. The non condensables cause a higher head pressure in the condenser. When this pressure is added into our calculation- it throws out the sum and so gives a false reading of subcooling.

Dehydration during Chiller Breakdown

The other purpose of evacuation is to dehydrate the system. Water, as we know, has a boiling point of 100°C at sea level, which is 1bar absolute or 760 Torr. As you start to drop the pressure, so correspondingly, the boiling point also drops. For example, water boils at the top of Mount Everest at around 68°C. If we continue vacuuming a refrigerant system, eventually we can remove all moisture by dropping the pressure below the saturation point of water. This works even in the winter in UK ambient conditions. Moisture in the system causes system failures and malfunctions leading to expensive breakdowns.

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Tags : chiller control systems chiller diagnosis chiller evaporators chiller expansion valves chiller refrigerant superheat maximus advantage r134a chiller refrigerant r407c chiller refrigerant r410a chiller refrigerant

Chiller Problems

Chiller Failure

To read more about chiller condenser fans hit the Tag at the top of the page.

Read more about rotary vane pumps at Wikipedia

11/10/2020
Maximus Chillers
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Chiller Maintenance Company

Category : Articles

Diagnosis of Chillers

One of the most important parts of a chiller maintenance company is the diagnosis. If this is done wrong, the wrong parts are ordered and the return job goes wrong.

News Article No.7

For us at Maximus Chillers, it is imperative that we get the diagnosis right, so the return job goes easy. On a maintenance visit, a detailed Tick Sheet is completed with all the necessary readings and adjustments.

Chiller Maintenance Company Case Study

One of our engineers was on a maintenance visit recently and he found an electrical fault with a relay. An intermittent fault- so the most annoying to diagnose. The relay interlocks the compressor A1 run signal on the start contactor. The fault causing the relay to drop out was the high pressure condition. The high pressure switch was found to be in good working order with continuity back to the relay, so the relay was deemed to be not switching intermittently. The relay was changed with the available stock on site and the machine went back into seamless operation.

State of the Art Equipment

At Maximus Chillers we know that incorrect test equipment can lead to incorrect diagnosis. That’s why we have the highest quality equipment which is regularly inspected, replaced or calibrated. With a Fluke multimeter with fused leads- we diagnose the most complicated of problems. Sometimes a wiring diagram is not available, or the machine has been modified. Even wires disappearing into a conduit and ending up on the other end of the chiller can be traced and effectively diagnosed. You can rest assured that with the ongoing maintenance by Maximus Chillers- we will extend the useful life of any chiller.

Chiller Maintenance Company Technical Support Desk

For over the phone diagnosis, our contract customers enjoy the full benefit of our technical support desk. Faults are often something and nothing, or are just to do with how the machine was restarted. If we can get a chiller away over the phone, that saves us time and that saves you: the customer money too. Just part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere.

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Expansion Valves

We at Maximus Chillers have a comprehensive range of expansion valves, on the shelf, in our stores at Head Office in Droylsden, Manchester. There are three commonly used types of expansion valve used on a chiller:

Pulse Expansion Valve

This is a simple design of a solenoid coil lifting a solenoid valve and opening the diaphragm in the expansion valve. This allows the refrigerant to pass from the high side of the system into the low side. A sensor either side of the evaporator feeds back to the controls. The controls work out the length of time the valve stays open and the length of time the valve stays closed. Quite a simple idea and quite reliable from our experience too. The replacement of parts are a straight swap.

Electronic Expansion Valve

Another type of valve we stock is the electronic expansion valve. Similar to the above, this valve uses a sensor either side of the evaporator to work out the superheat. Another method of working out the superheat is a sensor and a transducer. Either way amounts to the same thing: the controls work out the difference in temperature and saturation point. The mechanical part of the valve is a step motor which winds all the way shut when the chiller starts. This is so that the controls can register step 0. As the valve opens, the controls record the amount of steps. It therefore knows the position of the valve to regulate a close control of superheat.

Thermostatic Expansion Valve

A thermostatic expansion valve is a completely mechanical and stand alone part. The pressure in the bulb increases with temperature and so forces the valve open. We have the full range of orifices for the commonly used varieties of valve on the shelf. Each orifice is used for a different application, ranging from low temperature -40°C saturation, through medium temperature 0°C saturation, to high temperature 20°C saturation. High temperature applications include laser chillers- the secondary refrigerant cools the oscillator and the laser head.

HFC Refrigerant

HFC refrigerant is being phased down to 21% by 2030. This is in accordance with F-gas guidelines and the emission reduction measures as defined in the Kyoto Protocol. This refrigerant, however, still remains to be the most popular type amongst chillers, with new chillers coming off the production line charged with, most commonly, R407c and sometimes R410a. R134a is also a popular chiller refrigerant most commonly used in flooded centrifugal chillers. The more the phasedown starts to pinch, the more the incentive to use a lower GWP (global warming potential) drop in refrigerant. This extends the useful life of the chiller, therefore removing the need to build a new chiller, with the associated high amount of carbon emissions.

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Evaporators

Eddy Current Inspections by Chiller Maintenance Company

At periodic intervals according to the maintenance schedule, the end plates are taken off the evaporators and the tubes are inspected. We have calibrated eddy current instrumentation to assess the integrity of the evaporator tubing. This equipment uses electromagnetic coils to produce eddy currents, the electrical impedance is then measured. It picks up any cracks, pitting or corrosion. The conclusions are mapped onto a chart showing the tubes which are likely to fail. These tubes can be taken out of operation to prevent catastrophic system failure in the future. The system can then be pressure tested in accordance with F-gas leak testing requirements to prove the integrity of the system. Just part of the joined up, forward thinking of Maximus Chillers.

Chiller Maintenance Company Lagging

On our maintenance visits, one of a long list of checks is to check the insulation and vapour seal. If the lagging is not in place correctly, moisture from the air forms as condensation on the steel shell. This is not visible, so the condition of the steel can deteriorate dramatically over time. Where the lagging is in good condition, industry guidance states that it should not be removed to inspect. Where the lagging is in poor condition, however, it should be stripped back to the location of a good seal to inspect the integrity of the shell. For low temperature glycol or brine applications, rapid deterioration occurs as the shell is defrosting and re freezing between production cycles or defrost cycles. We heat treat the steel to remove all the moisture, then grind off any rust, before adding a two kinds of specialist paint available for sale at Maximus Chillers. We then match into the old lagging for a good join with our off the shelf varieties of lagging. The lower the temperature of the application, the greater the thickness of the lagging supplied.

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27/09/2020
Maximus Chillers
-

Air Cooled Chiller Maintenance

A nice day to carry out air cooled chiller maintenance at a new site we have taken over in the South East.

News Article No.6

Our engineer attended site at around 9am with the risk assessment method statement having been sent in advance. A site survey was carried out to see if there were any additional risks. Should there have been any changes- the RAMS have a section for the additional risks and control measures. After gaining a permit to work, our engineer was issued with a security pass to access the chiller compound. Three chillers are located in the compound which feed air handlers for a critical application. Two of the chillers are multiple system, scroll compressor, air cooled chillers. The other is a single system screw chiller.

Program Settings during Air Cooled Chiller Maintenance

A complete download of the program settings is available in our engineer’s phone. This is to cross reference the settings, should one of them be accidentally changed by the maintenance engineers. On site engineers are the first port of call for chiller trip outs, with the responsibility to get the plant up and running. We offer real time assistance, over the phone from our Technical Support Desk and can send user manuals in PDF form, direct to their computer. The settings were found to be nominal, so a detailed analysis of the alarm history was carried out:

Alarm History during Air Cooled Chiller Maintenance

In reverse date order, the alarm history of all the systems was interrogated. There had been several system shut downs to carry out the periodic maintenance by the onsite personnel. The electricity having been shut down, there was a subsequent oil pre heating timer in the history too. On Chiller 2, System 1 however, there had been several low pressure trip outs. Our engineer decided to start the maintenance with this system by carrying out a full diagnosis of the low side of the refrigerant system:

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Superheat during Air Cooled Chiller Maintenance

The system runs on R410a refrigerant. This refrigerant has higher operating pressures in comparison with other HFC refrigerants. It has an efficient temperature range which can be seen on a pressure enthalpy chart. Below or above this range- the refrigerant loses efficiency and so has a lower coefficient of performance. The most common saturation point for this refrigerant is 0°C which corresponds to a 7 bar suction pressure in the evaporator. Above this is the superheat of the refrigerant returning to the compressor. On this occasion there was found to be 26°C of superheat and a suction pressure of 4 bar- close to the low pressure trip out. After careful diagnosis, our engineer decided to focus his attention on the expansion valve:

Thermostatic Expansion Valve

There are 4 forces acting on a TEV:

Liquid line pressure coming from the condenser.
Versus
Suction pressure down the equalising line from the far side of the evaporator. This compensates for the pressure drop across the evaporator and shows the true compressor side pressure.

Spring pressure acting upwards and closing the valve.
Versus
Bulb pressure forcing the valve open.

To reduce the superheat, the bulb should have forced the valve open. The refrigerant charge in the bulb acts upon the bellows to achieve this. The reason for the malfunction, on this occasion, was found to be the failure of the expansion valve orifice. It had become jammed- causing a shortage of refrigerant in the evaporator and high superheat.

Latent Heat

Our engineer was carrying out the above fault finding with one compressor running and the other two being held off. This was to prevent a low pressure trip. Where chillers are left running with a high superheat condition, the reduced amount of latent heat causes a higher cost in electricity relative to refrigeration effect (COP) The refrigerant carries on superheating without absorbing latent heat- pointless and inefficient for a chiller.

Chiller Pump Down

For convenience, this chiller can be pumped down and valved off using the service valves. The evaporator can be worked on after breaking in procedures are carried out. Therefore, we have arranged for this to be carried out before fitting the new expansion valve parts. These chillers also have the ability to pump down the refrigerant on receiving a fault feedback from the electronic leak detector. This is an added measure to lower the environmental impact of refrigerant leaks.

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Subcooling during Air Cooled Chiller Maintenance

This is cooling the refrigerant vapour down, through the latent heat phase and then subcooling the liquid down further. On System 2 of the same chiller, a subcooling issue was identified. 21 bar/ 36°C saturation was normal for that system as defined by the fan speed controller. Now, the system pressure was higher at 28 bar/ 47°C saturation, so our engineer decided to work out the subcooling. A very high reading of subcooling was recorded at 28°C this was diagnosed to be due to non condensables in the refrigerant:

System Non Condensables

Non condensables are gases that will not condense, such as, air and nitrogen. If nitrogen is not vented properly and a deep vacuum then achieved, the gasses will remain in the refrigerant system. When calculating the subcooling, the readings work out incorrectly due the presence of the gasses. This can lead to false diagnosis. The remedy for the issue was to arrange a full refrigerant decant, pressure testing and dehydration, before charging with new refrigerant.

Efficiency

Having good subcooling values on a refrigerant system is critical to efficiency. Where there is no subcooling- the refrigerant has not fully rejected all the latent heat from the condenser. This can be seen when looking at a PH chart and plotting the pressures and temperatures. This heat remains in the refrigerant and adds to the system along with heat added from the compressor and heat from the process. This is another reason the coefficient of performance is reduced and so incurring increasing electricity costs for the plant.

Economizer

These chillers are also fitted with refrigerant economizers- one for each system. They work by diverting some of the refrigerant from the condenser, through a small expansion valve, then through a plate heat exchanger. The rest of the liquid refrigerant passes on the other side of the plate heat exchanger and so is further subcooled.

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Tags : air cooled chiller condensers chiller compressor systems chiller condenser high pressure faults chiller diagnosis chiller expansion valves chiller n+1 redundancy chiller refrigerant latent heat chiller refrigerant liquid pipes chiller refrigerant subcooling chiller refrigerant superheat direct expansion chiller evaporators f-gas chiller leak testing procedure flooded chiller evaporators lag chillers lead chillers reciprocating chiller compressors shell and tube chiller evaporators

To read more about chiller control systems hit the Tag at the top of the page.

Further reading on chilled water at Wikipedia

25/09/2020
Maximus Chillers
-

Chiller Maintenance Schedule

Category : Articles

The chiller maintenance schedule in essence is as follows:

What is the plant? According to the asset list for that particular contract.
What are we going to do with it? The checks, procedures and diagnosis in the pursuit of the maintenance of the chillers.
How often? The periodic maintenance schedule defining the required interval between visits to ensure seamless operation of the plant.

News Article No.5

Chiller N+1

N+1 is intrinsic in the development of a chiller maintenance schedule. N+1 means the amount of cooling required + the same amount again in parallel. It can also be represented as 2N. Two water system pumps are a good example: where the pipework splits in two- one pipe for each pump. When a pump fails, the redundant pump comes online. Chillers are arranged in parallel, in this way, on the water system. This redundancy allows for a stress free maintenance of the plant. The failed system can be rectified and brought back online while the redundant system takes the load.

Intervals of Chiller Maintenance Schedule

The intervals in the contract are influenced by the redundancy of the chillers on site. The less run hours the compressor does, the less maintenance is required. We at Maximus Chillers can tailor make a maintenance schedule exactly to your needs by looking at how much the chillers are used and how hard they work.

Load affecting Chiller Maintenance Schedule

For some applications, the chiller operates under a high load condition all the time, with a redundant system in standby. On other applications, the chiller works in minimal load conditions. Regardless of the load conditions, the chiller is critical to the cooling of buildings or for an industrial process.

Lead/ Lag of Chiller Maintenance Schedule

An important thing to remember is to balance compressor run hours and bearing wear by rotating the lead/ lag duty of the chillers. This can usually be done in the in the sequencer (if fitted) by changing a program setting. Otherwise, the switchover controls can be changed on the off/hand/run toggle switches. Where manual changeover is required, the onsite engineers are usually conversant with the procedure concerning the water system pumps, valves and controls. During the maintenance, the stop checks can be carried out on the redundant system, while the run checks are carried out on the system which is online.

Chiller Maintenance Schedule for Recip Compressors

Recip compressors require a log of the compressor run hours. This is because the valves and bearings should be changed at pre prescribed intervals as laid down by the schedule. Particularly important to reciprocating compressors are regular oil changes and oil sampling- a small change in the result of an oil sample can prevent a serious compressor smash up. A check list including the model number and serial number is completed on each visit and kept in a file on site. This file can be consulted during diagnosis and maintenance to decide on the beast way forward with an on going issue.

Chiller Maintenance Schedule for Air Cooled Condensers

Air cooled condensers can often be looked after by the onsite engineers in between maintenance visits. Just a quick brush down every few months is usually all it takes. Where the environment lends to a type of contaminant being collected on the condenser coils, an effective chemical is selected from our stores and used on the coil. Where there is an issue with the serviceability of the condenser, we can put together a plan to keep on top of it. We can even retrofit a new condenser- it’s what we call the MAXIMUS ADVANTAGE™

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Shell and Tube Evaporators

The shell is made from a heavy steel sheet rolled into a circle. The seam is welded together to form a cylinder. The tubes are pushed though the tube holders which are made from steel and are welded into the shell of the evaporator. The tubes are copper because of its good thermodynamic properties.

Direct Expansion Evaporators

Direct expansion is achieved in an evaporator with a thermostatic, or electronic expansion valve. The refrigerant enters the valve from the condenser as a high pressure, hot liquid. The pressure drop on the evaporator side of the valve makes the refrigerant flash off into a cold, saturation point liquid and vapour mix. The liquid boils off, absorbing latent heat through the inside of the copper tubes. On the outside of the copper tubes is the return water from the process, or the cooling of buildings.

The parts of the maintenance schedule that relate to DX evaporators are:

Oil Pooling

The inside of the tubes are in the clean environment of the fridge system. This means they do not become fouled. A tube insulating issue, however, can be caused on the inside by oil. If there are issues with the oil return system, the oil can pool in the evaporator. A low refrigerant charge can have the same effect. Written into the maintenance schedule are manual oil return and oil draining visits. During these visits, the monitoring of the refrigerant charge is also carried out.

Sensor Location

If a sensor is not located in its pocket correctly, or without sufficient heat transfer paste- it will read incorrectly back to the electronic expansion valve driver. This will cause the expansion valve to malfunction.

Pressurisation Units

A full maintenance of the pressurisation unit is carried out. This includes the pumps, controls and program adjustments as required. Incorrect pressure in the water system will cause a knock on effect of faults on the chillers.

Pump Sets

As above with chiller lead/ lag change over, water system pumps are manually changed over from lead to lag in the building controls. Carrying out this procedure reduces the chance of pump failure between visits. This is because it balances the pump run hours and so prevents bearing seizure after a long period not running.

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Flooded Evaporators

Flooded evaporators are the reverse of the above DX evaporators. The refrigerant is on the outside of the tubes, with water on the inside of the tubes. Gravity and refrigerant charge determine the refrigerant level in the condenser and evaporator. In between the two is located the liquid pipe with the orifice located in the pipe for the expansion of the refrigerant. The cooling water flows through the condenser tubes and off to the cooling towers. On the low side, the chilled water flows through the evaporator tubes and off to the process, or the cooling of facilities.

The parts of the maintenance schedule that relate to flooded evaporators are:

Tube Fouling

Because the condenser cooling water and chilled water systems are pumped through the pipes, the tubes become dirty over time. This occurs more often on the condenser as the water towers are open to atmosphere. Contaminants from surrounding buildings and factories gets into the water system and thermally insulates the tubes. This thermal insulation reduces the heat exchange through the copper tubes. The knock on effect is higher head pressures and eventually high pressure trip outs.

Specialist Cleaning Equipment

We at Maximus Chillers have in our stores the required equipment to carry out the cleaning of the tubes. Our engineers can attend site and liaise with the onsite engineers as regards the draining, strip down and lift out of the heat exchanger end plates.

Flushing Agents

A water sample is taken from the cooling and chilled water systems. These samples are sent off to our laboratory for analysis. Bacteria can build up in the water system causing slime- this can be rectified with a careful selection of chemical agents. Also, silt can build up- various chemicals are added to positively charge the silt and so carry it around the system to the strainer. Where the issue is caused by rust- an inhibitor can be added to prevent, or slow the oxidization of the steel.

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F-gas Testing of Leaks

The frequency of F-gas leak testing is determined by the size of the plant. This will be detailed in your F-gas file which is kept on site. Another record of this is kept by the chiller company at their registered office. The copies of the periodic leak testing sheets are kept by both parties. These detail the result of the test, refrigerant added to the system, refrigerant removed from the system and the required follow up actions. Some methods of leak detection are:

Visual Inspection

On each visit our engineers remove the coverings of the ends of the condensers and panels. This is to inspect the whole machine for a sign of a leak. Any potential leak is marked for future identification of where it is. A visual inspection will always be backed up with a further diagnosis such as:

Superheat and Subcooling

These readings are taken during a maintenance visit to determine the refrigerant charge of the chillers. The engineer, however, has to bear in mind that the subcooling and superheat readings can read abnormally due other reasons.

Bubble up Leak Spray

Various makes are available from the suppliers. Each engineer having his own preference. We at Maximus Chillers stock leak sprays and a wide selection of other materials.

Electronic Leak Detectors

Fixed

This type of leak detector is installed in the chiller low down in the panel. This is because HFC refrigerant is heavier than air. The leaking refrigerant will tend to pool in the bottom of the various panels around the chiller.

Portable

Each of our engineers carries a portable sniff tester. It comes with an extended tip to get into the most tight and awkward places. The leak detector has a replaceable element inside the unit. It also comes with replaceable tips which can be swapped out periodically. They come with a portable plug socket and transformer to charge the on board batteries after use in the field.

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Air Cooled Chiller Planned Maintenance

Tags : centrifugal chiller compressors chiller compressor failure chiller compressor lift and shift chiller compressor oil level chiller compressor strip down chiller compressor systems chiller compressor volumetric efficiency chiller condenser fan speed controllers chiller condenser fans chiller condenser systems chiller diagnosis chiller evaporators chiller expansion valves chiller n+1 redundancy chiller pressure transducers chiller refrigerant discharge pipes chiller refrigerant high pressure gauges chiller refrigerant latent heat chiller refrigerant leaks chiller refrigerant mass flow rate direct expansion chiller evaporators f-gas chiller leak testing procedure flooded chiller evaporators maximus advantage r134a chiller refrigerant screw chiller compressors screw compressor slide valve potentiometers scroll chiller compressors shell and tube chiller evaporators tighten chiller wiring

To read more about chiller expansion valves hit the Tag at the top of the page.

Further reading on chillers and the chiller maintenance schedule at Better Bricks

30/08/2020
Maximus Chillers
-

Chiller Service Company

Category : Articles

Electrical Testing

A chiller service company can carry out electrical testing and diagnosis even when a wiring diagram is not available- our engineers can trace the wiring around a chiller.

News Article No.3

Doing this often aids with the diagnosis even when there is a wiring diagram, as having your eyes on a component often makes more sense than a symbol. In any case, our engineers carry out system testing with Fluke multimetes and ammeters.

F-gas Leak Testing by Chiller Service Company

We also carry a range of thermocouples and probes to be used in conjunction with our calibrated digital thermometers. We use these along with comparators to carry out leak testing. After fitting the probes, we first have a visual look around for a sign of a gas leak. All parts of the pipework and system components are inspected. Then, we carry out a full refrigerant diagnosis to determine that the refrigerant system is operating with a full charge. Reports for each chiller are completed and filed in the onsite F-gas leak register. A history can be built up to assess the serviceability of the plant and the frequency of any leaks.

Chiller Service Company Monitoring

Where intermittent faults are concerned, on site monitoring is required. If the job is not progressed on each visit, there is little point in a call out. We carry out tests during monitoring and ensure that the wiring is tight. Hopefully, waiting for the fault to occur whilst next to the machine. Alongside this, we rely on feedback from the end user, as regards, the symptoms and the circumstances of the chiller when the fault occurred. From this we extrapolate the diagnosis and decide the next step to take. This may be to attempt to move the fault to another machine or, at least eliminate one thing each visit.

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Chiller Service Company Evaporators

Shell and Tube

These have a rolled steel shell, welded down the seam with and end plate on either end. The water system pipes can be bolted to the sides or the end. The endplate can be removed for access to the waterside of the tubes. A strainer is fitted to the inlet to catch any foreign objects that may have been carried around the water system. Inlet and outlet gauges are fitted for the monitoring of the water system readings during a visit.

Flooded

On larger chillers, the screw or centrifugal compressor is mounted directly on top of the flooded evaporator. The refrigerant is in its liquid phase on the outside of the tubes. These are arranged in a rack extending through the length of the shell. The warmer process water running through the tubes causes the refrigerant to boil off. A sight glass is usually available to check the state of the refrigerant evaporating on the copper tubes. The suction from the top of the evaporator goes round a baffle so as to prevent the slug back of liquid refrigerant into the compressor. The refrigerant flow into the evaporator is controlled by the expansion valve…

Expansion Valves

This takes the form of a fixed size orifice on the liquid line in between the shell and tube condenser and the flooded evaporator. The size of the orifice previously being calculated to match the mass flow rate of the refrigerant dictated by the compressor. Some newer systems have a variable orifice for the more efficient running of the plant. This is controlled electronically along with the loading of the compressor, relative to the available load.

Multiple System N+1

Smaller DX evaporators are usually multi system. This gives an N+1 redundancy of the plant. Indeed, when one side of a 2 system evaporator is having service work carried out, the other side continues to operate normally. Thinking ahead and allowing for additional capacity is essential when the application is critical, such as, a data centre or a hospital. When a redundant system comes online due to a failure- getting the failed system back up and running is a matter of urgency. For this we offer same day delivery of parts and a fully stocked mobile workshop.

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Chiller Service Company Condensers

Various configurations are employed to ensure good air flow through the condenser fins. The most popular being a ‘v’ condenser as the surface area is increased with this design. Powerful fans are used to reject the air and heat upwards and away from the chiller. Where system location causes the recirculation of air, duct work can be fitted to direct the air away from the chiller. The pressure is monitored using a HP gauge.

Pressure Transducers

Johnson Controls

A popular kind of pressure transducer that is used on condensers is Johnson Controls. These can be bolted onto the refrigerant discharge pipe to sense the system pressure. They have a 5vdc input that comes into the transducer on a red wire, a black wire is the ground and a white wire is the signal back to the fan speed controller. The transducer has a minimum to maximum range, so a chart can be used to determine if the signal is reading back correctly. On chillers where the transducer is wired directly in the controller- calibration can be carried out to offset the readings.

Keller

Another kind of pressure transducer is the 4-20mA type. It sends a mA signal back to the controller or the fan speed controller. 4mA is the minimum position, so this relates to the minimum of the transducer pressure range.

R134a Refrigerant

R134a refrigerant operates at a lower pressure in a condenser than the other commonly used HFC refrigerants. If you were looking for a chilled water set point of 6°C in the UK ambient for example, the R134a refrigerant saturation on the high side of the system would be around 36°C Latent heat from the water system and heat added into the refrigerant from the compressor are rejected from the condenser. As the refrigerant passes down the condenser tubes, cool air blowing across the outside of the tubes, cools the refrigerant vapour down through the latent heat phase and into a subcooled liquid.

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Chiller Service Company Compressors

Centrifugal Compressors

This kind of compressor has a lower volumetric efficiency compared with the positive displacement compressors below. This is because the refrigerant is compressed using centrifugal force off the tip of the impeller, instead of being mechanically compressed. The advantage of this kind of compressor is a high mass flow rate of refrigerant. These compressors are used in factories where a large amount of chilled water is required to cool the process. They are also used in countries where district cooling is used. The chillers are arranged in rows in a chiller hall and are piped into the district cooling loop.

Screw Compressors

Oil used to lubricate the bearings is also used to create a seal between the rotors. Computer aided design (CAD) software and computer numerical control (CNC) grinding machines are used in the construction of screw rotors. The shape of the rotors is designed to compress the refrigerant along the screw. The length of the screw that is available to compress the refrigerant can be adjusted with a slide valve. Any stage of loading between 0- 100% can be achieved. This is regulated with a slide valve potentiometer. Screw compressors are very reliable and have a long service life. They also have a low vibration reading which ensures a lower instance of refrigerant leaks around the compressor.

Scroll Compressors

A service free compressor. Service free assuming that the rest of the system is functioning correctly. This kind of compressor relies on oil migration around the system. The oil is entrained along the inside of the pipework, around the system and back to the compressor. An oil level sight glass is fitted into the body of the compressor at the required level. Refrigerant shortage can cause the oil to stay in the bottom of the evaporator, causing a low oil level condition in the compressor. We can be scheduled to attend site to drain the oil, then pump new oil into the compressor.

Compressor Failure

When any of the above compressors fail, you are in safe hands with Maximus Chillers. We have the capability to lift and shift the compressor to our remanufacturing facility for a full overhaul. The reason for the failure is diagnosed to ensure the new compressor does not fail for the same reason. Improving the reliability of your plant and extending its life is what we are all about- if we can reduce your service costs- that makes us happy! All temperatures and pressures are recorded to ensure the replacement compressor goes into seamless operation.

Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere- The MAXIMUS ADVANTAGE™

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To read more about chiller diagnosis hit the Tag at the top of the page.

Read more about pressure sensors on Wikipedia

16/08/2020
Maximus Chillers
-

Planned Preventative Chiller Maintenance

Featuring planned preventative chiller maintenance, which is part of a series of longer, in depth articles.

News Article No.2

This time concentrating on the checks, adjustments and diagnosis our engineer carries out while on site. We can extend the life of your plant and reduce energy costs- just with the effect of our maintenance. As well as completing a detailed checklist, which is sent to your office in PDF form, our engineer carries out extensive F-gas leak testing.

Planned Preventative Maintenance of Chiller Controls

The first part of the maintenance is carried out to the controls of the redundant systems. This is because all the pressures and temperatures should be reading the same. If not, this is an opportunity for:

Sensor Calibration

Before calibrating a sensor that is reading out, our engineer carries out a diagnosis to assess the serviceability of the sensor. With NTP (negative temperature coefficient) and PTC (positive temperature coefficient) sensors, the resistance is taken at a given temperature, which is then compared with a chart. With pressure transducers the 0-5vdc feedback signal is analysed to see if it is within the allowable tolerance. Once this diagnosis is complete and the sensor is deemed to be in good working order, our engineer will then calibrate the sensor. A password is entered into the PLC (programmable logic controller) to gain access to the service menu. From here, he can select the particular sensor, then offset it by the required amount. A lot of controls are not linear, that is to say, a sensor reading 2°C high being reduced by 2°C may not calibrate correctly. An amount of trial and error is often required. Also, monitoring the sensor against a digital thermometer at various temperatures is carried out.

Program Settings and Timers

Each program setting and timer in the various menu levels is checked against the previous maintenance checklist. Sometimes these are changed accidentally by the onsite engineer when looking for something else- it is easily done.

Planned Preventative Chiller Maintenance of Safety Chain

Each component on the safety chain is manually tripped or the fault condition is replicated to cause the device to trip. This part of the PPM (planned preventative maintenance) is essential to ensure the safety chain protects the chiller during a fault condition. Compressor failure or evaporator freeze up can occur with dramatic cost implications. We routinely prevent small problems, such as a faulty switch, becoming big problems.

Planned Preventative Chiller Maintenance of Wiring

Each wire on the chiller is checked for tightness including the fans (on air cooled chillers) This includes the compressor motor connectors and compressor contactor contacts. Loose line wiring will cause breaker and fuse faults. Loose control wiring will cause error messages and chiller faults. This is a call out in between visits that can be eliminated. With the effect of our maintenance, any chiller becomes more reliable and has lower energy costs.

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After the above stop checks are carried out, system run checks are carried out:

Superheat

Using R134a refrigerant as an example, the refrigerant pressure will be 1.9 bar at 0°C This refrigerant is in the HFC (hydrofluorocarbon) family- a commonly used refrigerant. If the refrigerant vapour returning to the compressor is excessively superheated- this is a sign of system issues. Here are some of the causes for a high superheat condition:

Refrigerant Shortage

Not enough latent heat being absorbed by the refrigerant in the evaporator. This allows the refrigerant to carry on superheating with the available heat load. Refrigerant leak testing is required to identify any leaks. The history of maintenance checklists can be consulted to see if the issue has been deteriorating over several visits.

Expansion Valve Failure

A thermostatic expansion valve operates with a higher superheat value, whereby an electronic expansion valve has a much closer control. In either case, our engineer will be accustomed to the nominal readings.

Thermostatic Expansion Valves

This type of valve is operated with a power element and orifice. A bulb is clamped onto the suction pipe which is connected to the power element via a capillary tube. The power element is pressurised with the same refrigerant as in the chiller. Some of this refrigerant is in its liquid phase, so with an increase in temperature, there is a corresponding increase in pressure. This pressure acts against the diaphragm and so pushes the orifice open. The orifice allows more refrigerant through the valve. When load conditions change and there is a reduction in heat load, the reverse happens- the orifice closes and reduces the amount of refrigerant through the valve. When the power element looses its charge- the orifice shuts down causing a high superheat condition. A low pressure trip out can also occur.

Electronic Expansion Valves

This type of valve uses sensors on the liquid and vapour sides of the evaporator, or a transducer and sensor vapour side of the evaporator. This is so the program can work out the superheat value. If the sensors are faulty, the valve will not operate correctly and a high superheat condition may occur. If the step motor or driver have failed- replacement parts are required.

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Subcooling

This is the measurement of the refrigerant condition in the condenser. Air cooled condensers are particularly popular in the UK as the ambient conditions make them very efficient. Shell and tube condensers are used on lager systems- these are cooled down using a water tower. When there is a refrigerant shortage, the liquid does not stay in the condenser long enough for it to subcool sufficiently. Some of the refrigerant stays in its vapour phase. With not enough latent being rejected in the condenser- the chiller’s COP (coefficient of performance) will be reduced. This means high energy consumption relative to the refrigeration effect of the chiller. This condition can be remedied with a scheduled visit from one of our team.

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To read more about chiller control systems hit the Tag at the top of the page.

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26/07/2020
Maximus Chillers
-

Chiller Maintenance Checklist

Category : Articles

Introducing a series of in depth news articles, this time featuring the chiller maintenance checklist:

News Article No.1

This article has been written with you- the customer in mind. Read below for practical advice on how to keep your chillers in the best condition.

Each day when you walk round, you can check to see if your plant is starting to malfunction. Become accustomed with the usual readings to help you diagnose the faults.

Here are the things to check for and how to remedy them:

Water System Pressure

Keep an eye on the pressure in the water system.

Small Chiller Maintenance Checklist

On a small chiller, there will be a water outlet pressure gauge. Make a mark on the gauge where the pressure is when the chiller is in good working order. You can use this mark to notice if the pressure is starting to drop off.

Strainer

The most common cause for low water system pressure is a blocked strainer. It is usually a ‘Y’ type with a bolted fitting. With the chiller off and the water system valves closed, unscrew it and check for debris. If it is blocked, make a note of how long it took to block, then add the cleaning of the strainer into the periodic maintenance schedule.

Pump

Ensure the pump rotation is correct by checking that the cooling fan is sucking into the pump. If it is going backwards: isolate electrically, then swap any 2 of the 3 phase wires. Brush down the inlet to the cooling fan to ensure good air flow and a cool pump motor.

Large Chiller Maintenance Checklist

On a large chiller, the water system pressures may be available in the controller- have a look through the menus. The pressure will be measured in bar. Another popular method on a large chiller is a flow meter. This may be a stand alone device on the chiller panel, or on a control panel nearby. It will read in m3/hr. Check to see if the pressure or flow is lower than usual. If so, ring one of our trained professionals.

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Water System Temperature

The chiller should be:

Matching the load and running continuously.
Loading and unloading in sequence with other chillers.
Going through a cycle and achieving set point.

In any case, you will become accustomed with the usual chilled water temperature according to varying load conditions. If the plant is struggling to achieve set point, or is running higher than usual- this is a sign of system faults.

Walk along the chillers that feed the same water system and make a log of the faults showing on the controllers.

Here are the things to check when you have high water system temperature:

Small Chiller Maintenance Checklist

Low Pressure

If the chiller has a low pressure gauge, look to see if the pressure is lower than usual. If so, this is a sign of refrigerant shortage in the plate evaporator. A scheduled visit from one of our trained engineers to carry out a pressure test can be arranged.

Breakers

Look for any breakers that have tripped in the panel. One reset can be carried out by a qualified onsite electrician. If the fault reoccurs- ring our support team. If the scroll compressor has tripped, check to see if the compressor is hot. If so, isolate and do not attempt a restart.

Condenser

A blocked condenser will inhibit the rejection of heat. Brush it down and give it a rinse with water. A common occurrence onsite with some condenser designs is a panel being left off with the chiller running! This happens when the onsite engineers are fault finding another issue with the chiller. The fans will suck through the opening as this is the easiest path. The gauge will be higher than usual as the condenser builds in pressure. A high pressure trip out will occur.

High Pressure Switch

To locate the switch- first identify the discharge pipe. It is the smaller of the 2 pipes on the compressor. The high pressure switch will either be bolted onto the pipe, or a thin pipe will lead from the discharge to the frame of the chiller. In any case, you are looking for a small box with a button and a wire leading to the panel. Press the button and you should hear it click. If this fault reoccurs- ring our technical support desk.

Large Chiller Maintenance Checklist

Suction

Should there be a refrigerant shortage, the controller will display a pre alarm like 'suction limiting' This is the controller preventing the compressor from loading up, so as to prevent a low pressure trip out. As above, one of our team of engineers can be sent to site to resolve the issue.

Discharge

If the controller is showing 'discharge limiting' this is a sign of a condenser issue. A full strip down and cleaning of the tubes may be required. Ring our technical support desk for further advice.

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Chiller Remote Monitoring

We at maximus chiller can install remote monitoring systems to your chillers so we can fault find and diagnose from a laptop. This means we can give you real time advice over the phone. Now you are accustomed with our chiller maintenance checklist, you can give feedback regarding the plant to assist our engineer.

Parts

For our contract maintenance customers: a range of commonly used parts are kept onsite to reduce downtime. We can give practical, step by step advice on the fitting of parts. We often carry out video calls with our customers, as chiller data plates, parts and components can be easier to show than describe.

Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere- The MAXIMUS ADVANTAGE™

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