Chiller Repair Company

Chiller repair company for a row of grey air cooled chillers in Saudi

Chiller Repair Company

Maximus Chillers is renowned in Saudi Arabia and around the world as a chiller repair company because we can do anything. Read on to see the repairs that were carried out for a customer of ours in Riyadh…

Evaporator Chiller Repair Company

This site had issues with the quality of the chilled water which is used to cool the process. Therefore, we had recommended that a plate heat exchanger be fitted to the water system to separate the process water from the water supplied to the chillers. This was because the process water was becoming contaminated with plastic particles from the extrusion of pipes which are manufactured on site. We also recommended to fit cleanable Boll filters with a 200 micron filter size. There are strainers available on the inlet to each chiller, but these only catch the larger particles.

Evaporator Tube Cleaning

This visit was before the above repairs were carried out, so we decided to clean the evaporator tubes. We valved off and drained down each evaporator, in turn, and removed the end plates. We have state of the art chiller tube cleaning equipment which we keep in the stores on site. This equipment is used for our customers around the Middle East. We have another tube cleaner at Head Office for use in the UK, offshore and for The Spanish Office.

Decontamination

We set up our equipment next to each chiller and carried out the decontamination process. A lot of contaminants were removed which were causing thermal insulation…

Thermal Insulation

This is the condition where contaminants prevent heat exchange from occurring between the chilled water and the refrigerant in the evaporator. The system therefore runs inefficiently- it stays on longer and uses more electricity. Eventually, the system deteriorates into a safety shut down.

Chemical Clean and Rinse Out

After the decontamination process, we used a chemical which removed any scaling which had occurred. After this had been carried out, we thoroughly rinsed out all of the evaporators.

0161 370 7193

service@maximuschillers.com

Contact Form

Controls Retrofit by Chiller Repair Company

One of the chillers had controls that were defunct and problematic. We sourced a new controller in the UK along with the associated sensors and transducers.

Compressors

This controller was selected because it is capable of running two systems with a Bitzer screw compressor on each. These compressors operate a slide valve which has 4 stages of loading.

Electronic Expansion Valves

The expansion valves are electronic and stand alone. This was convenient as they did not need to be integrated into the controls of the chiller. They work out the superheat by making a calculation between the pressure and temperature of the refrigerant in the evaporator. This is exactly the way our engineers make the calculation when they use an app on their phone.

Fan Speed Controllers

Another convenience found was that the fan speed controllers fitted were also stand alone- again removing the need to integrate them into the controls. A high pressure transducer is fitted to the condenser which senses the refrigerant pressure. A program in the fan speed controller then speeds up or slows down the fans according to demand. This maintains the correct saturation point, therefore giving the required amount of subcooling.

Rip Out by Chiller Repair Company

It is not in the mindset of a chiller engineer to rip the wiring out of a panel. He spends most of his time, painstakingly repairing complicated electrical faults. However, going at a panel with a pair of snips and some screwdrivers can be quite good fun when he gets into it. Not all of the wiring is ripped out anyway: the three phase wiring can be left in place along with the common neutral.

Wire In

The controller was fitted onto the DIN (Deutsches Institut für Normung) rail and then each of the wires was connected from the controller to the terminal strip. From there, the wires were connected to the contractors, the relays, the transformer and other components in the panel. The external wiring around the chiller was also connected and tested for earth leaks.

Commissioning

A parameter list came with the controller, so our engineer spent a day programming each setting. The following morning, after a cup of coffee, he powered up the chiller, a timer counted down and the first compressor started up. After another timer counted down, the second compressor started up too. Minor adjustments were made during the day, then the chiller went into seamless operation.

0161 370 7193

service@maximuschillers.com

Contact Form

Compressor Swap Out by Chiller Repair Company

One of the compressor motors had burned out which had been identified on a previous visit. The oil had also been analysed and was found to be contaminated. On this visit, our engineer valved off the compressor and removed it from the chiller using specialist lifting equipment. The new compressor having been sent to site prior to the visit. Then, he lifted the new compressor into position. The wiring was connected, the mounting bolts were tightened, the pipework was bolted on and a leak test was carried out.

Oil Changes

A new compressor sump comes with a full charge of fresh oil. However, the oil migrates around the system meaning that contaminated oil will return to the new compressor. For this reason, several oil changes were carried out during the visit until a satisfactory oil test was achieved.

Monitoring

The oil was found to be at the correct level according to standard industry guidelines. The discharge and suction pipe temperatures were recorded during varying load conditions and were found to be nominal. Finally, a vibration monitor was fitted to the compressor to show up any imbalances. This was an important last step as excessive vibrations would reduce the new compressor’s lifespan.

Related Articles:
Chiller Tube Cleaning Service

Chiller Controls

Screw Chiller Compressor Maintenance

Industrial Chiller Repair

Hit the Tags at the top of the page to navigate your way to our extensive library of further reading on this subject.

Read more about a DIN rail on Wikipedia.


The rock of Gibraltar at night where chiller maintenance is being carried out

Gibraltar Chiller Maintenance

With The Spanish Office now open down the road, it has never been easier to carry out Gibraltar chiller maintenance. In this article, we will be focusing on a visit by our overseas engineer from Head Office in the UK. He visited Gibraltar to carry out training to our engineer from The Spanish Office near Malaga.

Gibraltar Chiller Maintenance Contracts

We have a three year maintenance contract for the chillers at a facility on The Rock. This was the issue that was rectified while our engineers were on site…

Water System

Our engineer from The Spanish Office had noticed that the refrigerant system readings had deteriorated in between maintenance visits. Our overseas engineer confirmed that the this was correct. The performance of the machine had gone down and it was struggling to achieve set point. The same amount of load was available from the building.

Remote Plant Room

A remote plant room is located inside the building on the third floor. It is where the BMS (building management system) panel is located which starts the pumps and other plant.

Supervisor

The BMS panel is also linked to the supervisor (a computer) in the facilities manager’s office on the first floor of the building. The supervisor is where the timers are adjusted to bring the chillers and other plant on and off according to a schedule. A low ambient thermostat is also available to hold the chillers off on cold days in the winter.

Pump Data Plate

Whilst in the plant room, our overseas engineer noticed that Pump 1, which was feeding the chiller at the time, had recently been changed. This pump was one of two pumps in a pump set. On interrogating the data plate, then reading the manual for that pump, our engineer noticed that the specifications were wrong for this particular chilled water system. Therefore, he decided to set the toggle switch on the BMS panel to pump 2 which was the redundant pump.

952 110 798

info@maximuschillers.es

Contact

Improved Readings during Gibraltar Chiller Maintenance

By the time our engineers returned to the chiller compound at the back of the building, the chiller had begun to load up. It had previously been limiting its loading to prevent a trip out. Now the water system readings had improved to optimum values, the chiller got on top of the load. It then unloaded to match the load coming from the building.

Old Pump Leaking

The customer informed our engineers that their onsite maintenance engineer had recently changed the pump with one from their stores. The one in their stores had the same mounting plate dimensions so it was a quick fix without the need to buy a new one. The old pump had been found to be leaking water from the shaft seal connecting the pump to the electric motor.

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

Obsolete Parts

As we work on all chillers, we have to be able to do anything. This is because parts are sometimes obsolete or unavailable. Therefore, we have the technical ability to retrofit new parts to old chillers. This dramatically saves in the carbon footprint of buying new plant.

Extending Lifespan in Gibraltar with Chiller Maintenance

We can extend the life of your chillers by at least 10 years with our thorough maintenance procedures. Some problems can be rectified whilst we are on site at no extra cost. This is because each vehicle in our fleet is a mobile workshop with a treasure trove of commonly used materials. Repairs can also be carried out at the end of the visit as we carry an extensive range of parts too.

952 110 798

info@maximuschillers.es

Contact

Controller Swap Out

When a controller malfunctions and is found to be obsolete, it can constitute a big problem. However, it is no trouble at all for Maximus Chillers as we have Carel controllers on the shelf.

Strip the Panel

First, we strip the wiring, the electrical components and the old controller from the panel. We keep the 3 phase wiring, the common neutral and the transformers. This is because we reuse them for the new controls.

Fit New Components

Next, we fit the new controller, the condenser fan switches, the sensors and the transducers. Electronic expansion valves and compressor variable speed drives can also be fitted at this stage if required.

Wire Up

Each wire between the controller and the various components in the panel is wired up one at a time. The external components around the chiller are also wired back to the panel.

Commissioning

The final part of the job is the commissioning phase where the program settings and the fan switches are adjusted. This process gets the machine to settle down into seamless operation. A day or two is usually taken to do this, with a courtesy visit arranged a week later to iron out any teething problems.

Supply Chain for Gibraltar Chiller Maintenance

Where a compressor needs rebuilding, it can be lift and shifted to be rebuilt at our compressor remanufacturing facility at Head Office in the UK. We can also carry out strip down and rebuilds on site using our engineers from The Spanish Office. We have suppliers in Malaga for consumables and refrigerant. We also have a weekly shuttle service from the UK to replenish the Spanish Office. This is because we have excellent suppliers in the UK who provide second to none technical support in the selection of parts. UK equipment is also of exceptional quality, so things like vacuum pumps and refrigerant gauges are replenished from the UK too.

Related Articles:
Saudi Chiller Commissioning

Chiller Condenser Tube Cleaning

Offshore Marine Chiller Service

Hit the Tags at the top of the page to navigate your way to our extensive library of further reading on this subject.

Read more about Gibraltar on Wikipedia.


Process chiller repair service being carried out on evaporator and expansion valve

Process Chiller Repair Service

We at Maximus Chillers have just carried out a process chiller repair service for a customer of ours in the North West. The expansion valve on System 1 had been found to have failed and this was the return visit to rectify. There is N+1 redundancy built into the plant, so there was not an immediate hurry to attend site. When our engineer diagnosed the fault, he had a look in our customer’s stores as he knows our customer likes to keep spares. Sure enough- there was a spare expansion valve on the shelf, so he took it and put it in the chiller panel ready for the job.

News Article No.27

Process Chiller Repair Service to Jammed Valve

What had happened to the old expansion valve was that the mechanical part had worn down and jammed part open. This meant that the refrigerant circuit would run for a while with a poor superheat reading, but would trip out on low pressure when more scroll compressors started running.

Isolate Electricity

Our engineer disabled System 1 and removed the fuses. This was to prevent an accidental start up during the repairs. He used his lock off padlock, to which, he was the only engineer with a key.

Refrigerant Decant

The full refrigerant charge was recovered into 2 small recovery cylinders which were taken to the refrigerant storage cage. This is a segregated area to reduce the risk of explosion in the event of a fire. It is also shielded from direct sunlight to reduce refrigerant pressure inside the cylinders.

Hot Works Permit during Process Chiller Repair Service

The next stage of the job was to remove the failed expansion valve, so a Hot Works Permit needed to be obtained from the Maintenance Department. It was counter signed by the permit issuer and our engineer with the fire watch time added to the additional information section.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

Related Articles:
Chilled Water System EEV Service

How do Chillers Work? Expansion Valves

F-gas Chiller Leak Testing

Hit the Tags at the top of the page to navigate your way to our extensive library of further reading on this subject.

Read more about electronic expansion valves on the Carel website.


Offshore oil rig showing chiller service being carried out in marine environment

Offshore & Marine Chiller Service

North Sea Offshore & Marine Chiller Service

On a previous visit for offshore & marine chiller service on an oil rig, our customer had shown us to a large air cooled chiller. His complaint was that it was tripping out all the time when there was nothing wrong it. Complicated ‘in house’ controls, where a string of PCBs, plugged into each other were found in the panel. We recommended a controls retrofit and received the order to carry out work…

Finicky Controls

All of the finicky control PCBs were removed from the panel and placed in the electrical recycling skip.

Offshore & Marine Chiller Service to Control Wiring 

The control wiring was removed and grouped together according to colour. This was because the same wiring was going to be re used to re wire chiller.

Inverters

Two Danfoss inverters were installed into the panel. These were to provide a VSD (variable speed drive) for two large screw compressors.

Electronic Expansion Valves

Danfoss EEVs were easily brazed into place as both systems could be pumped down and valved off. This part of the fridge system was then nitrogen pressure tested then vacuumed according to standard industry guidelines.

Fan Speed Controllers

Both systems had a Danfoss fan speed controller fitted to the chiller frame to control the condenser fans. Then, the control transducers were wired in to the FSCs. This made them stand alone and capable of independently controlling the head pressure of each system.

Danfoss Chiller Controller

The controller in the photo is capable of running the inverter drives for the compressors and the electronic expansion valves. It was wired in, one wire at a time: first the Inputs, then the Outputs and finally the power supply.

Offshore & Marine Chiller Commissioning Service

We always carry out commissioning in the morning as this is the best time of the day to solve problems. It was time for a cup of coffee and a deep breath. Our engineer had only re wired one panel previously and he was also a long way from the office.

Switch On

When he switched the power supply on, there were no immediate problems, so he waited for the for the timer to count down. System 1 started and after a while System 2 started too. There were a few teething problems with the settings, but then the chiller settled down. No more spurious trip outs.

0161 370 7193

service@maximuschillers.com

Contact Form

Controller used in offshore chiller service
Cheap and very reliable

Offshore & Marine Chiller Service in Liverpool

A bulker had got into difficulties in the Irish Sea and been towed to Liverpool for service. It was discovered that a rope had got wrapped around the propeller. Aside from this, one of two chillers which are used for the cooling of the living quarters had tripped out. The Chief Engineer had therefore decided to kill two birds with one stone. Most of the crew were from around Tanger Med in Morocco and so spoke only a little English. They also have limits as to how far they will go with a fridge system. Not to worry though: all we need is to see the plant and we can take it from there...

Seawater Cooled

The plant had a sea water cooled condenser which was fed via a pump set in an adjoining plant room.

Offshore & Marine Chiller Service to Controller

The controller alarm message stated that there was a low pressure condition in the evaporator. On interrogation of the menu, however, the pressure of the evaporator was found to be 7 bar which was the same as in the condenser.

Reset

Our engineer therefore decided to follow through the reset procedure. The alarm cleared and the machine started up. Then, it pumped down to 1 bar and tripped out on the same fault.

Liquid Line Solenoid Valve

While this was happening, our engineer was quick to notice that the liquid line solenoid valve had not activated. He decided to manually jack it open with his test equipment and the refrigerant rushed through okay.

Liquid Line Solenoid Coil

Having decided that the valve was okay, he then investigated the coil. The connection box and the wiring was found to be in poor condition.

Isolate

He then isolated the power supply and checked that it was dead.

Rewire

The wiring was cut back and he re made the connections onto the solenoid coil without using the connection box. Then, he insulated the area with a special compound.

Test Operation

Now to see if he had got the diagnosis correct. He powered up the chiller and carried out a run test- all readings were found to be nominal and the machine went back into service.

0161 370 7193

service@maximuschillers.com

Contact Form

Planning for Offshore & Marine Chiller Service

The main part of the planning for an offshore visit is done on the previous job. A detailed list of the required parts, materials, refrigerant, tools and equipment is composed on our Offshore Manifest Sheet. The questions and headings have been designed to prompt an engineer into thinking about all aspects of the job in detail.

Preparation for Offshore & Marine Chiller Service 

Having emailed the above mentioned sheet to Head Office, we cross reference the information with the engineer while he is still offshore. All this preparation is to ensure that the upcoming job goes as planned. There would be nothing worse than to have to postpone the job due to a lack of preparation.

Steel Chests

We have several steel chests that we use for shipping to oil rigs. After the parts and materials arrive at Head Office, they are checked off, one at a time into the shipping chests. Then, the necessary tools and equipment is checked off too.

Offshore Stores

Our customers also have their own equipment in their stores. They have things like fittings and fuses too. This is a good backup for when something is unforeseen, or if something breaks.

Related Articles:
Chiller Controls

Chiller Commissioning

Chiller Controls Company

Gibraltar Chiller Maintenance

Hit the Tags at the top of the page to navigate your way to our extensive library of further reading on this subject.

Read more about accommodation platforms on Wikipedia.


Large air cooled chiller failure showing refrigerant cylinders and vacuum pump

Chiller Failure

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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

Contact Form

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!

Related Articles:
Packaged Chiller Service

Chiller Breakdown

Water Chiller Service of Evaporator

Industrial Chiller Repair Service

Hit the Tags at the top of the page to navigate your way to our extensive library of further reading on this subject.

Read more about how a solenoid valve works on The Engineering Mindset.


Showing how do chillers work - brass expansion valves inside machine

How do Chillers Work? Expansion Valves

In this article we are going to explore: how do chillers work- expansion valves. They are also referred to as a metering device, as they control the flow of refrigerant into the evaporator. Read below for an insight into the 4 main types that are used on chillers…

How do Chillers Work - Electronic Expansion Valves

This is a refrigerant control which uses a mechanical valve operated by a step motor. A step motor opens the valve according to the number of steps in between the closed and the open positions. This step motor is controlled by a program in the chiller controller…

On Board Comparator

Every engineer has a comparator app on his phone and a set of comparator sliders in his tool case. The controller has sensors fitted to the evaporator and an in built comparator for the refrigerant which runs through the system. The comparator is a scale which compares the pressure of the refrigerant to the corresponding saturation point. Saturation point is another way of describing the boiling point of the liquid refrigerant.

Superheat

The above algorithm is needed to decide the position of the step motor. A pre programmed amount of superheat (the temperature above saturation) is programmed into the controller. This prevents compressor failure due to liquid refrigerant slug back.

Efficiency

Because the above is controlled by a step motor and a microprocessor, the superheat is closely controlled to as low as 1°C. A low superheat value is one of the factors which contributes to a machine running more efficiently.

0161 370 7193

service@maximuschillers.com

Contact Form

How do Chillers Work - Solenoid Expansion Valves

This is a very simple expansion valve. It is just a solenoid valve fitted into the liquid line which is operated by a solenoid coil. The control of this valve is very similar to the above. The difference is that the program works out how long to keep the valve open and how long to keep it shut.

How do high side float expansion valves work when welded into steel ammonia chillers pipework
Refrigerant control on flooded system

How do Chillers Work - High Side Float Expansion Valves

The photo shows this type of valve as used on an ammonia chiller. This kind of chiller is a flooded system where all of the refrigerant is stored in its liquid phase on the low side of the system. As load increases: more refrigerant boils off in the evaporator- it is sucked into the compressor- discharged into the condenser and then arrives as a liquid at the float valve. When the chamber in this valve fills, it lifts a float inside which is made of steel. The float operates a switch which sends volts to the liquid pipe solenoid valve. When this valve opens, it lets the liquid in the float chamber to pass into the evaporator. Having done this, the float drops back down and the valve closes again. The closing of the valve maintains the pressure difference between the high side and the low side of the system.

0161 370 7193

service@maximuschillers.com

Contact Form

How do Chillers Work - Thermostatic Expansion Valves

There are 4 forces acting on a TEV: the power element v spring and liquid line pressure v suction pressure. The expansion valve has been designed to balance these forces.

Power Element

A bulb is fitted to the suction pipe near to the compressor. This bulb is charged with the same refrigerant that is running in the chiller system. It is connected to the power element using a capillary tube (photo at the top of the page) When the temperature rises in the evaporator, liquid refrigerant boils off in the bulb, this forces a diaphragm to open in the power element.

Spring

A needle located on the outside of this diaphragm pushes the spring down. This opens the expansion valve and lets more refrigerant through.

Liquid Line Pressure

The liquid line is the inlet to the expansion valve and carries the refrigerant arriving from the condenser.

Suction Pressure

The pressure drop on the far side of the expansion valve is maintained by the sucking action of the compressor.

Mass Flow Rate

The above allows for a high mass flow rate when the evaporator warms and a lower mass flow rate when the evaporator cools.

Liquid Line Solenoid Valve

To prevent refrigerant passing into the evaporator during off cycles, a liquid line solenoid valve is often used. This type of system usually pumps the evaporator down before the compressor stops. Shortly before the compressor starts back up again, the liquid line solenoid valve opens, the pressure increases in the evaporator and then the compressor starts.

Equalizing Line

This is usually a copper pipe which connects the expansion valve to the far side of the evaporator. It compensates for the pressure drop across the evaporator. It also detects the pressure of the suction pipe at the same location of the sensing bulb. This allows the TEV to accurately adjust the superheat.

Hot Gas Bypass

Some chillers, like laser chillers, require a very close control of setpoint. Sometimes the deadband can be as narrow as 0.2°C. If the compressor were to stop and start all the time to achieve this- it would fail very quickly. Therefore, a hot gas bypass can be used to allow the compressor to carry on running when the chiller achieves setpoint. A solenoid valve opens which allows the discharge hot gas to bypass the expansion valve and return to the suction. It can open and close as many times as needed to achieve a very close control, while at the same time allowing the compressor to run normally.

How do Chillers Work - Expansion Valve Flash Gas

This is the term that describes that portion of the liquid refrigerant which, in any expansion valve, instantly evaporates after it passes through. When this happens, the absorption of latent heat cools the remaining liquid refrigerant in the evaporator to the required saturation temperature.

Related Articles:
How Do Chillers Work

Chilled Water System EEV Service

Chiller Maintenance Company

Planned Preventative Chiller Maintenance

How do Chillers Work? Compressors

Process Chiller Repair Service

Hit the Tags at the top of the page to navigate your way to our extensive library of further reading on this subject.

Read more about thermostatic expansion valves at the Danfoss website


Example of chiller types: 2 grey containerised ammonia chillers with air cooled condensers on top

Chiller System Types

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

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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

Industrial Refrigeration Ammonia

Glycol Chiller Maintenance

Hit the Tags at the top of the page to navigate your way to our extensive library of further reading on this subject.

Watch a video from The Engineering Mindset about chiller types on You Tube


How does a grey centrifugal chiller work showing the main system components

How do Chillers Work?

How do chillers work? This is a question we get asked quite a lot from our subscribers. So, in this article I am going to explain the science and also talk you round the main chiller components…

The Basic Refrigeration Cycle

Weather it is the large centrifugal chiller like the one in the photo, or the refrigerator in your kitchen- most cooling systems work according to the basic refrigeration cycle which involves vapour compression. Two scientific principals are at work: latent heat and the pressure temperature relationship. Four chiller components are needed: evaporator, compressor, condenser and expansion valve.

Sensible heat

Heat energy that can be sensed is called sensible heat. Imagine a pan of water with a flame under it and a thermometer resting in it. You are watching the flame licking up the bottom of the pan and you are also watching the thermometer going up, obvious- right? The heat energy from the flame going into the pan is sensible heat.

Example

Now imagine if we pumped a liquid through a heat exchanger at 0°C with warm water being pumped through the other side of the heat exchanger. Some heat energy would exchange into the cold liquid and warm it up, for example, by 6°C. This is sensible heat.

0161 370 7193

service@maximuschillers.com

Contact Form

Latent Heat

Latent is the Latin word for hidden. Something less obvious happens when a pan of water gets to its boiling point of 100°C. You continue watching the flame licking up the bottom of the pan, but the temperature stops going up, strange- right? You carry on watching for a good while and the thermometer still does not go up? Then, eventually- the water boils into steam and the thermometer starts going up again. All of the heat energy that was going into the pan while the thermometer was not going up was latent heat. Latent heat was being absorbed into the water to cause it to change its state into steam. All of this hidden heat caused the liquid atoms to shake apart and become a gas.

Example

Now let’s look at the above example again, but this time including latent heat. At Step 5, a different liquid is pumped through the heat exchanger at 0°C which is also its boiling point. The amount of sensible heat, in our example, is still 6°C. Between the outside of the bubble and Step 1, there is 3°C of sensible superheat above the boiling point. Between Step 4 and Expansion, there is 3°C of sensible subcooling below the boiling point. The latent heat is inside of the bubble which, as you can see, has a considerable size. We measure sensible and latent heat energy using kJ/kg.

How does a chiller work on a PH diagram

The Pressure Temperature Relationship

How we produce the above liquid at 0°C is the second scientific principle...

Higher Pressure

If you increase the pressure of a substance- the atoms are pushed together and so they get hot. The higher the pressure- the higher the temperature.

Lower Pressure

If you decrease the pressure of a substance- the atoms spread apart and so they go cool. The lower the pressure- the lower the temperature.

Refrigerant

R134a is a refrigerant that has a pressure of 1.91 barg, relative to a temperature of 0°C.

Refrigerant Saturation Point

The above temperature of 0°C is also the boiling point of R134a. This boiling point can also be called the saturation point because no more heat can be added to the liquid before it boils. The refrigerant liquid is full of heat- or saturated.

0161 370 7193

service@maximuschillers.com

Contact Form

How do Chillers Work with Evaporators? 

This is a heat exchanger which is in between two other chiller components: the expansion valve and the compressor. The expansion valve is a restriction in the chiller system and so there is a pressure drop into the evaporator. The compressor sucks from the evaporator and so maintains this pressure drop. This is the pressure temperature relationship: the lower the pressure- the lower the temperature. Liquid refrigerant flows through the evaporator at 1.91 barg and 0°C. It boils off absorbing latent heat, then it superheats, in our example, by 3°C above its saturation point. The evaporator has absorbed heat energy from the water on the other side of the heat exchanger.

How do Chillers Work with Compressors?  

A bicycle pump is a compressor- notice how it gets hot when you inflate a tyre. This is the pressure temperature relationship: the higher the pressure- the higher the temperature. Therefore, the compressor also adds heat energy into the system. The refrigerant is sucked into the compressor from the evaporator as a cold, low pressure gas at 1.91 barg. It is then compressed into a hot, high pressure gas which is discharged from the compressor at 8 barg.

How do Chillers Work with Condensers? 

The hot, high pressure gas being discharged from the compressor is cooled down with fans which suck air through the fins of this heat exchanger. The gas goes through its latent heat phase again, but this time condensing from a gas and into a liquid. It is then subcooled, in our example, by 3°C below its saturation point into a hot, high pressure liquid. The heat energy absorbed in the evaporator and the heat energy added to the system by the compressor is rejected into the surrounding air.

How do Chillers Work with Expansion Valves?

The hot, high pressure liquid at 8 barg arrives from the condenser at the inlet of the expansion valve. The expansion valve could be seen as being a tap which is partially closed. This restriction causes the refrigerant to back up behind the expansion valve inlet. The refrigerant that gets through the valve and into the evaporator expands into a cold, low pressure liquid/ vapour mix. The vapour is called ‘flash gas’ and is as a result of the refrigerant expanding. Vapour is another word for a gas.

How do Chillers Work with Set Point?

This basic refrigeration cycle continues until the setpoint is achieved and the controller stops the compressor. After some time, the water warms up by a couple of degrees and the controller starts the compressor back up.

Related Articles:
Shell & Tube Chiller Evaporator Maintenance

Chiller Compressors

Chiller Condensers

Chilled Water System EEV Service

How do Chillers Work? Expansion Valves

How do Chillers Work? Compressors

Hit the Tags at the top of the page to navigate your way to our extensive library of further reading on this subject.

Read more about vapour compression refrigeration on Wikipedia

 


Man commissioning a chiller in Saudi wearing head gear

Saudi Chiller Commissioning

We arranged the trip to carry out Saudi chiller commissioning for our Company Director and overseas engineer Dave Thompson. 2x 500kw air cooled chillers had been positioned at high level on a gantry. These were at the back of a newly constructed building at a factory in Jeddah. The factory produces plastic water pipes used for buildings and industry. Their own pipework, produced onsite, was used for the water systems of the plant in this article.

Water System Check Valves

There are two underground water system reservoirs for the plant. A check valve is fitted below the water line on the inlet pipe feeding all of the pumps. This ensures that water is available to the pumps on start up, despite the reservoirs being below the pumps.

Saudi Chiller Commissioning of Chiller Pump Set

The chiller pump set sucks water from the underground chiller reservoir. It then discharges the water through a plate heat exchanger, then it flows up to the chillers. The chilled water then returns 5°C cooler back to the underground chiller reservoir.

Saudi Chiller Commissioning of PHE Pump Set

Another pump set sucks from the separate underground process reservoir and discharges through the other side of the above mentioned plate heat exchanger. The water is chilled by around 5°C which can be adjusted with a pressure regulating valve on the outlet of the PHE. This chilled water then returns to the underground process reservoir.

Saudi Chiller Commissioning of Process Pump Set

A third pump set also sucks from the above mentioned underground process reservoir. It then discharges up to a ring main which goes along the top of 6 lines. Then, it drains down into plastic extrusion moulding machines to cool the newly formed plastic pipe. It does this at just the right rate to prevent bending and distortion. After this, the chilled water drains at gravity pressure back into the underground process reservoir.

0161 370 7193

service@maximuschillers.com

Contact Form

Control Panels for Pump Inverters

All of the pumps run on inverter drives which saves a significant amount of electricity. These drives are located in three panels- one for each pump set. A spare inverter is available in each panel for easy switch over in the event of failure. A touch screen pump control display is fitted to each panel. Each display is wired into a PLC.

Touch Screen Central Control

The PLCs in each panel are in turn wired into a Schneider Electric touch screen central control interface. This is located on the front of the middle panel. All of the analogue sensor and transducer inputs are wired into this interface from around the plant. The underground process reservoir temperature sensor was found to be reading 4°C high, so an offset was put into the program. The digital outputs go from here to the various components around the plant.

3 Way Valve

One of these components is a 3 way valve on the plate heat exchanger. This valve regulates the percentage flow of water through the PHE, relative to the percentage of bypass to the chillers. In high load conditions, 100% of water is pumped through the PHE. With no load, 0% of water goes through the PHE with full bypass to the chillers. In a low load condition, the valve modulates at between 0% and 100%. All of these scenarios achieve a close control at 20°C in the underground process reservoir.

Saudi Chiller Commissioning of Filtration Systems

Chiller Evaporators

The chiller evaporators are protected by a ‘y’ strainer on each inlet.

PHE Chiller Side

The plate heat exchanger also keeps contaminants from the process reaching the evaporators of the chillers. This prevents the premature failure of the evaporators and also prevents heat exchange issues due to thermal insulation.

PHE and Process Bollfilter

Both of these water systems go through a Bollfilter back flush system. As the difference in pressure between filter inlet and outlet reaches a predetermined level, the back flushing operation is initiated with a green light being illuminated. This feature prevents the need to manually clean the filter at scheduled intervals. During the visit, however, these filters were overwhelmed by the residue left in the pipes and a narrow 100 micron filter size. The maximum difference in pressure was exceeded and the filtration system yellow warning light became illuminated. The filters were stripped down, cleaned and reassembled.

‘Y’ Strainer in Parallel

The onsite engineer who had assisted in designing the system had the foresight to build a second filter into the water system. This ‘y’ strainer runs in parallel to the above Bollfilter and ensures seamless operation of the factory in the event of a blocked Bollfilter.

0161 370 7193

service@maximuschillers.com

Contact Form

Start Up during Saudi Chiller Commissioning

On first start up of the chillers, they were both found to be tripping on high pressure and not loading up. The chillers run on R134a which is a low pressure refrigerant in the UK. In Saudi Arabia, however, the ambient is around 40°C. This translates to an operating pressure of between 15 bar and 18 bar depending on loading and water temperature.

Loading Solenoids

Unloader switches are available on each system. These feed back to the PLC, from here the program energises the loading solenoids. They had been set to 14 bar which was the cause of the unloading issue. Our overseas engineer set the switches to 19 bar.

High Pressure Switches

He then changed the high pressure cut outs from 15 bar to 20 bar.

PRVs Checked during Saudi Chiller Commissioning

The pressure relief valves vent at 23 bar which is enough of a difference in pressure from the high pressure cut out.

Low Load Trips

Because only one line was running at the time of commissioning, one of the chillers was found to have tripped on a low temperature related trip. This fault had occurred the following morning when the water temperature had become too low due to the minimum run time of the compressors. The freeze up set point was also found to be too high at 7°C. Our overseas engineer entered a password into the front end of each chiller and modified the parameters to prevent this fault re occurring.

Full Load Testing

The water system temperature was allowed to build up to 30°C when production in the factory was offline. Then, the chillers were ran in anger until set point was achieved. An efficient superheat value of 3°C was recorded on all of the systems. This is due to electronic expansion valves being fitted. When the factory came back online, the systems were found to be off cycling or unloading to match the load.

Chiller Redundancy

Redundancy has been considered in the capacity of the chillers to allow for future factory expansion and systems being offline during repairs.

Related Articles:
Global Chilled Water System Service

Gibraltar Chiller Maintenance

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

Read more about Jeddah on Wikipedia


Nitrogen cylinder and regulator with gauges attached for f-gas chiller leak testing

F-gas Chiller Leak Testing

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…

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

Related Articles:
Chilling Plant Service

Chilled Water System EEV Service

Water System Service of Evaporator

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Breakdown

Chiller Fault Finding & Diagnosis

Chiller Commissioning

Air Cooled Chiller Condenser Testing

Chiller Call Out

Process Chiller Repair Service

Industrial Chiller Repair Service

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


Large chiller, refrigerant cylinder, brazing equipment and tools during chiller service company visit

Chiller Service Company Visit

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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!

Related Articles:
Chilling Plant Service

Chilled Water System EEV Service

Water System Service of Evaporator

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Breakdown

Chiller Fault Finding & Diagnosis

F-gas Chiller Leak Testing

Chiller Commissioning

Air Cooled Chiller Condenser Testing

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


Carel controller showing R134a refrigerant readings during preventative chiller maintenance

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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:

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

Related Articles:
Air Cooled Chiller Planned Maintenance

Water Chiller Maintenance

Process Chiller Maintenance Visit

Chilled Water System Maintenance

Centrifugal Chiller Maintenance

Industrial Chiller Maintenance

Air Cooled Chiller Condenser Maintenance

Glycol Chiller Maintenance

Chilling Plant Maintenance

Process Chiller Maintenance

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

Watch a video about chiller efficiency and the coefficient of performance


Blue recovery unit with a grey recovery cylinder during a chiller breakdown

Chiller Breakdown

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...

0161 370 7193

service@maximuschillers.com

Contact Form

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…

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

Related Articles:
Chilling Plant Service

Chilled Water System EEV Service

Water System Service of Evaporator

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Service Company

Industrial Chiller Service

Chiller Service Company Visit

Chiller Fault Finding & Diagnosis

F-gas Chiller Leak Testing

Chiller Commissioning

Air Cooled Chiller Condenser Testing

Chiller Call Out

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


Maximus Chillers sign outside our chiller maintenance company office

Chiller Maintenance Company

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

Related Articles:
Air Cooled Chiller Planned Maintenance

Water Chiller Maintenance

Process Chiller Maintenance Visit

Chilled Water System Maintenance

Centrifugal Chiller Maintenance

Industrial Chiller Maintenance

Air Cooled Chiller Condenser Maintenance

Glycol Chiller Maintenance

Chilling Plant Maintenance

Preventative Chiller Maintenance

Chiller Maintenance Contract

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

Further reading on F-gas enforcement reforms at RAC Magazine


Large white chiller being inspected to compose a chiller maintenance schedule

Chiller Maintenance Schedule

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™

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

Related Articles:
Air Cooled Chiller Planned Maintenance

Water Chiller Maintenance

Process Chiller Maintenance Visit

Chilled Water System Maintenance

Centrifugal Chiller Maintenance

Industrial Chiller Maintenance

Air Cooled Chiller Condenser Maintenance

Glycol Chiller Maintenance

Chiller Maintenance Company

Chilling Plant Maintenance

Preventative Chiller Maintenance

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


Chiller compressor failure of blue Grasso in enclosure

Chiller Compressors

System Testing for Chiller Compressors

Chiller compressors fail often as a result of ineffective servicing and system testing. At Maximus Chillers, we carry out extensive tests during our visits to ensure that small problems are resolved before they become big problems. If we notice a reading starting to become abnormal, we can carry out the diagnosis and then remedy the problem. Some of the compressor readings we monitor are:

Temperature of Chiller Compressors

The suction, discharge, motor windings and bearing temperatures are recorded for comparison to previous visits. These are often available in the PLC for the chiller, or our engineer can take the readings with his test equipment. Problems with the oil cooler can be the cause of higher compressor temperatures, the system running outside of its nominal operating conditions is another reason. Magnetic drive systems have an advantage as they do not use oil.

Accelerometer

Portable vibration sensors are carried in of each of our company vehicles. This is an accelerometer to measure vibration. Along with other system readings, we keep an on going record of the vibration levels around the compressor. When internal components are coming out of alignment due to wear, this causes an out of balance condition in the compressor. This, in turn, causes a knock on effect- causing other components to go out of balance. Catching this condition early will prevent a compressor smash up resulting in the replacement of expensive internal components.

Oil Analysis for Chiller Compressors

Another way of preventing big problems from occurring is periodic compressor oil testing. Samples are taken, usually on alternate visits, which are sent off to a laboratory for analysis. The acid level is tested to provide pre warning of a potential compressor motor windings burn out. This is because acid in the compressor oil rots through the electrical insulation on the motor windings. The presence and quantity of white metal and yellow metal is analysed too. This is a window through to a component starting to wear inside the compressor.

0161 370 7193

service@maximuschillers.com

Contact Form

Screw

The compressor in the photo is a screw compressor. It operates with ammonia refrigerant. This refrigerant is usually used for low temperature applications, mainly associated with food production. This compressor, however, has a 1°C refrigerant saturation and is used to cool computer rooms. Common causes of compressor failure on this kind of compressor are:

Leaking Castings on Chiller Compressors

The various compressor components are sealed together using ‘o’ rings or paper gaskets. ‘O’ rings are especially prone to leaks due to work hardening and flattening of the sealing face. The system can be pumped down and the compressor valved off. Then, our lift and shift team can remove the compressor to our remanufacturing facility for strip down.

Leaking Shaft Seal

The mating surface of a shaft seal has a mirror smooth finish. This is to reduce friction and aid with a better seal. Over time, this starts to wear, causing an ineffective seal with a leak of refrigerant and oil. A service visit can be arranged to change the shaft seal on site. The shaft couplings can be split, the shaft seal can then be removed and replaced. A quick job, then the machine is up and running again.

Slide Valve Potentiometer

This is an electronic device with a slide attached to the moving compressor slide valve. The device has a start and an end position programmed into it during commissioning. The potentiometer converts the slide valve position, usually into a 4-20mA signal which is fed back to the chiller PLC. They are prone to reading out, or the reading being jammed in one position. This results in a trip out from the controls, as the controller is not able to determine the true position of the compressor slide valve. We have an off the shelf stock of slide valve potentiometers for the various compressor range. A service visit can be arranged to replace the part after diagnosis has been carried out. The controls operate the loading and unloading solenoid valves to change the position of the slide valve.

0161 370 7193

service@maximuschillers.com

Contact Form

Centrifugal

Centrifugal compressors are a very reliable kind of compressor but when they go wrong, they can go wrong in a big way. Compressor overhaul is expensive, this can be carried out onsite, or a better option is a lift and shift to our remanufacturing facility. Proximity sensors are usually fitted to monitor the distance between the impeller and the casting. This is an added protection along with the other sensors and transducers around the compressor.

MCS

We are on account with Micro Control Systems- an American company who specialise in building panels to order for specific chiller compressors. We easily fit this control system to any compressor to control the loading of the vanes in accordance to the available load from the process. The control panel has previously been fitted to other machines of the same model number, so any teething issues have already been ironed out. Maximus Chillers can achieve seamless operation of your plant.

Oil System for Chiller Compressors 

Newer centrifugal compressors are oil free so as to eliminate any of the service issues relating to oil. There are a substantial amount of compressors, however, that use oil to lubricate the bearings. This kind of compressor, if properly serviced, can last for 50 years. The oil system picks up impurities which are caught by various filters. These filters can be changed or cleaned according to the prescribed service schedule. Our engineers make sure that spares are ordered and kept onsite prior to a visit.

Cost Effective

Our visits and ongoing upkeep of your plant saves money. Money spent as a preventative measure saves so much more money in the long run. With competitive prices on specialist internal centrifugal compressor parts- Maximus Chillers completes the picture. When compressor failure occurs, you are in safe hands with years of industry experience invested in each of our engineers.

0161 370 7193

service@maximuschillers.com

Contact Form

Scroll

These are some issues affecting a scroll compressor:

High Discharge Pressure

With high discharge pressure, there is a corresponding increase in discharge temperature. This means that the compressor is operating beyond its recommended values. The cause of this is often a poorly maintained condenser. Especially on industrial chillers, there can have been gaps in the schedule where the condenser was not correctly serviced. This condition is often rectified easily by an onsite engineer by giving it a brush down. Where the fins are bent over- we carry a specialist tool to straighten them back out- how they came out of the factory. We also use different formulas of chemicals to rinse the various kinds of dirt from deep within the fins.

High Suction Pressure on Chiller Compressors 

Some chillers are used where very high water temperature can come back from the process if the chiller were to be off line for a short period. Usually, this happens in factories where certain industrial processes are being carried out. When the onsite engineers start the plant back up, the chiller experiences a high heat load to deal with.

MOP Expansion Valves

Maximum operating pressure expansion valves limit the pressure in the evaporator to a given level, regardless of the available heat load from the process. They do this by having a limited amount of liquid refrigerant in the bulb. When this runs out, the power element cannot push the orifice open any further- thus limiting the suction pressure. This is important to prevent scroll compressor failure as it prevents putting added strain on the compressor motor windings due to high suction pressure.

Oil and Refrigerant Shortage

Where there is a shortage in refrigerant, there follows a low oil level condition. The refrigerant mass flow rate carries the oil around the system and back to the compressor. This is greatly impaired when the chiller is short of gas. The oil cools the compressor and lubricates the shaft bearings. These bearings and other internal components wear down and seize causing failure. Maximus Chillers can put together a package to minimise chiller compressor failure.

People also like this page:
Centrifugal Compressor Remanufacturing

Related Articles:
Screw Chiller Compressor Maintenance

Chiller Parts Supplier

Air Cooled Chiller Condenser Maintenance

Shell & Tube Evaporator Maintenance

Scroll Chiller Compressor Maintenance

Chiller Controls

Centrifugal Chiller Compressor Maintenance

Chiller Condensers

Reciprocating Chiller Compressor Maintenance

Chiller Controls Company

How Do Chillers Work

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

Read more about impellers which are used in centrifugal compressors at Wikipedia


PLC and relay board in a panel during chiller service company visit

Chiller Service Company

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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™

Related Articles:
Chilling Plant Service

Chilled Water System EEV Service

Water System Service of Evaporator

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Breakdown

Industrial Chiller Service

Chiller Service Company Visit

Chiller Fault Finding & Diagnosis

F-gas Chiller Leak Testing

Chiller Commissioning

Air Cooled Chiller Condenser Testing

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

Read more about pressure sensors on Wikipedia


Large air cooled brown chiller with test equipment during planned preventative chiller maintenance

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

0161 370 7193

service@maximuschillers.com

Contact Form

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.

Related Articles:
Air Cooled Chiller Planned Maintenance

Water Chiller Maintenance

Process Chiller Maintenance Visit

Chilled Water System Maintenance

Centrifugal Chiller Maintenance

Industrial Chiller Maintenance

Air Cooled Chiller Condenser Maintenance

Glycol Chiller Maintenance

Chiller Maintenance Schedule

Air Cooled Chiller Maintenance

Chiller Maintenance Company

Chilling Plant Maintenance

Chiller Maintenance Contract

Chiller Maintenance Service

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

Further reading on the subject of preventive maintenance on Wikipedia


Mirror looking for leak during chilled water system eev service

Chilled Water System EEV Service

Chilled water system EEV service was being carried out because the mechanical parts had failed. This particular valve is prone to this fault. It is an OEM electronic expansion valve, so our technician found the voltage for the motor and found a similar part with the same amount of steps.

The EEV driver was found to be functioning satisfactorily. Sometimes, depending on how the mechanical part of the EEV has failed, the driver can be overloaded and burned out.

Electronic Component Refurbishment

Where electronic parts, such as the EEV driver, are found to be burned out- Maximus Chillers has a refurbishment laboratory at head office. We have the capability to strip down the component and fault find where it has blown. Usually it is quite simple: the jammed mechanical part of the valve has burned out the motor for example. More complex fault finding and component replacement on the circuit board can be carried out also. Another option is to replace the driver with a like for like swap or retrofit to a different driver.

0161 370 7193

service@maximuschillers.com

Contact Form

Pump Down for Chilled Water System EEV Service

The chiller was pumped down and valved off. This saves on the time and recovery vessel to pump the refrigerant out.

Remove and Replace

Once pumped down, our engineer removed and replaced the valve, sealing it on its knife edge seal. The wire was passed up the conduit and into the panel. The wiring colour scheme was different on the new valve, so some time was taken to ensure it was wired up correctly.

Restart after Chilled Water System EEV Service

After leak testing, the refrigerant system valves were opened back up and the plant switched back on. The correct superheat and subcooling values were achieved concluding a successful visit.

Related Articles:
Chilling Plant Service

Water System Service of Evaporator

Process Chiller Service

Chiller Fan Deck Service

Packaged Chiller Service

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Service Company

Chiller Breakdown

Industrial Chiller Service

Chiller Service Company Visit

Chiller Fault Finding & Diagnosis

F-gas Chiller Leak Testing

Chiller Commissioning

Process Chiller Repair Service

Read about Danfoss electronic expansion valves


Translate