Chiller Efficiency

Red chiller with lantern illuminating the internal components showing test equipment for checking chiller efficiency

Chiller Efficiency

In this article we will be looking at some of the basic reasons why chiller efficiency is reduced...

News Article No.18

A Blocked Condenser Decreases Chiller Efficiency

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

Evaporator Thermal Insulation Decreases Chiller Efficiency

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

Blocked Strainer

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

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Refrigerant Shortage Decreases Chiller Efficiency

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

Refrigerant Leak Repairs

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

F-gas Register

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

Blocked Pump Fan

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

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Waste of Money

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

Maintenance Visits Improve Chiller Efficiency

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

Mobile Workshop

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

Kilowatt Hour Meters

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

Scheduled Chiller Maintenance

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

Technical Support Desk

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

Related Articles:
Air Cooled Chiller Condenser Testing

Shell & Tube Chiller Evaporator Maintenance

F-gas Chiller Leak Testing

Planned Preventative 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 how to improve chiller efficiency on The Engineering Mindset | Click Here


Man commissioning a chiller in Saudi wareing 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.

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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 of 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 factory engineer who had designed 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.

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

Read more about Jeddah on Wikipedia | Click Here


Two large air cooled chillers during condenser testing

Air Cooled Chiller Condenser Testing

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

News Article No.16

Air Cooled Chiller Condenser 1 Testing

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

Fan Speed Transformer

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

Medium Fan Speed

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

Compressor Protection

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

Monitoring

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

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Air Cooled Chiller Condenser 2 Testing

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

Blocked Condenser

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

HP Reset

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

Chemical Clean

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

Non Condensables

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

Cool Building

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

Air Cooled Chiller Condenser 3 Testing

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

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Air Cooled Chiller Condenser PRV Testing

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

Air Cooled Chiller Condenser 4 Testing

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

F-gas Leak Testing

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

Dehydration

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

Air Cooled Chiller Condenser Testing and Calibration

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

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

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Chilled Water System EEV Service

Water System Service of Evaporator

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Breakdown

F-gas Chiller Leak Testing

Chiller Fault Finding & Diagnosis

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

Read more about pressure sensors on Wikipedia | Click Here


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.

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Chiller Company Service Low Pressure Visit

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

Refrigerant Pump Out

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

Leak Testing during Chiller Company Service Visit

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

Brazing during Chiller Company Service Visit

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

F-gas Pressure Test

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

Vac Pump

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

Recharge and Run Test

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

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Refrigerant Economizers

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

Expansion Valve

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

Flash Gas

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

Efficiency

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

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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

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 | Click Here


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™

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Shell and Tube Evaporators

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

Direct Expansion Evaporators

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

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

Oil Pooling

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

Sensor Location

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

Pressurisation Units

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

Pump Sets

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

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Flooded Evaporators

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

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

Tube Fouling

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

Specialist Cleaning Equipment

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

Flushing Agents

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

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F-gas Testing of Leaks

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

Visual Inspection

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

Superheat and Subcooling

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

Bubble up Leak Spray

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

Electronic Leak Detectors

Fixed

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

Portable

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

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Chilling Plant Maintenance

Preventative Chiller Maintenance

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A pile of completed chiller maintenance checklists on a table

Chiller Maintenance Checklist

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

News Article No.1

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

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

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

Water System Pressure

Keep an eye on the pressure in the water system.

Small Chiller Maintenance Checklist

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

Strainer

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

Pump

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

Large Chiller Maintenance Checklist

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

0161 370 7193

service@maximuschillers.com

Contact Form

Water System Temperature

The chiller should be:

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

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

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

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

Small Chiller Maintenance Checklist

Low Pressure

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

Breakers

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

Condenser

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

High Pressure Switch

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

Large Chiller Maintenance Checklist

Suction

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

Discharge

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

0161 370 7193

service@maximuschillers.com

Contact Form

Chiller Remote Monitoring

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

Parts

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

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

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

Read more about chillers on Wikipedia | Click Here


Engineer carrying out process chiller service with yellow and black cylinder

Process Chiller Service

Maximus Chillers has just carried out process chiller service to a flooded evaporator. The refrigerant seal on a four bolt, flanged coupling had been found to be leaking liquid refrigerant. There was no possibility to valve off that section of the machine, as the flooded evaporator is the storage vessel for all of the charge of the system in its liquid phase.

Refrigerant Recovery during Process Chiller Service

Our high capacity refrigerant recovery unit was set up next to the machine to carry out the task. 55 kg of refrigerant was recovered in a short time into our recovery cylinder. This refrigerant was collected for recycling after the job was completed.

Stainless Steel

Our unit is made from stainless steel because this metal works well with ammonia.

Condenser for Process Chiller Service

The condenser is made from tubing which is connected to ‘u’ bends on either end. These ‘u’ bends send the condensing refrigerant back along the next tube in the opposite direction. This process, back and forth allows time for the refrigerant to condense into a liquid. Fins are pressed around the tubing to increase the surface area and help to dissipate more heat from the refrigerant. A condenser fan is fitted to suck the air through the fins and so reject the heat.

Reciprocating Compressor

A four cylinder reciprocating compressor is fitted to the unit to provide the pressure difference to pump the refrigerant into the above mentioned condenser. It has an air cooled electric motor fitted which is open drive. This is because ammonia would corrode the windings of the motor if a semi hermetic compressor were to be used. Semi hermetic meaning that the windings, stator and rotor of the motor would be internal to the system. The motor is fitted in the vertical position with the four cylinders opposing each other on the central crank shaft.

Controls for Process Chiller Service

For safety reasons controls are fitted to the unit. These include:

HP Switch

If the recovery cylinder were to become over filled, the pressure would build up to a dangerous level. The TARE and the ullage need to be calculated prior to the job to prevent this from happening. The below mentioned liquid pipes have been designed with pressure issues in mind, but somewhere on the system would be the weakest point. This would burst causing a catastrophic refrigerant leak. The whole charge of the machine and all the refrigerant in the recovery cylinder would leak to atmosphere. The HP switch is set by the engineer on site to the correct level given the ambient conditions. This takes into account the temperature of the refrigerant and the safe operating pressure of the vessel.

0161 370 7193

service@maximuschillers.com

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Refrigerant Liquid Pipe

Steel Braided

The refrigerant in its liquid phase is pumped into the above mentioned unit down a steel braided liquid pipe. The steel braiding is to provide additional protection from the pipe being damaged on the outside. Damage like being driven over by a forklift truck, or having sharp objects coming into contact with it. Also, the braiding helps to prevent bursts when pressure builds up on the inside. This can be due to a restriction, malfunction of system components or vessel overfilling.

PTFE

The inner part of the pipe is PTFE. Other types of plastics and compounds corrode due to the toxicity of ammonia. Polytetrafluoroethylene is the chemical name for this compound, it is a fluorocarbon solid and is considered to be non reactive.

Fittings

There are various metric and imperial thread types that can be used. This depends on the fitting size on the machine and the fitting size and type going onto the recovery unit. We carry a wide range of fitting types to step down and step up in size. We can go between male to female types and use male to male and female to female where necessary. We carry adaptors to go from metric to imperial thread types.

Remote Access during Process Chiller Service

We carry an extensive stock of liquid pipes that can be connected end to end to provide remote access. We will always try to get the recovery equipment as near as possible to the plant, but when this cannot be achieved, we can arrange access up cat ladders or the side of a building. We can use our lift and shift team to arrange the hauling of all the required equipment and ancillaries to any location. Just part of what we call the MAXIMUS ADVANTAGEAny Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. Contact our office for prices for the above mentioned pipes.

Process Chiller Leak Service

The flanged coupling was unbolted and the failed refrigerant seal was removed. The new seal was fitted from our full range of sizes that we keep on the shelf in our stores. Our engineer bolted the flanged coupling back up to the correct torque setting.

Pressure Leak Test

A nitrogen pressure leak test was carried out to ensure the integrity of the system with the result being a pass.

Dehydration Process

As the system was open to atmosphere, air had got into the system which carries moisture content. The moisture and non condensables were removed down to a near perfect vacuum using one of our high capacity vacuum pumps.

0161 370 7193

service@maximuschillers.com

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Charging of Refrigerant

The photo shows the charging of a cylinder of refrigerant into the system in its liquid phase. The cylinder has a dip tube fitted for ease of handling. Once the pressure in the system and the cylinder equalized, remaining refrigerant was drawn into the system during the operation of the plant.

Run Testing

The sight glasses and level glasses were found to be at the optimum level under the normal running conditions of the plant. As it is a flooded system, there was found to be a low superheat value. A high subcooling value was achieved with the use of a subcooler. Our engineer monitored a full cycle of an hour and a half: compressor temperatures and oil level were found to be within normal operating limits.

Remote Service Monitoring of Process Chiller

The process chiller can be remotely monitored via a data uplink through the internet. Our office continued to monitor the plant for some days as it went into seamless operation.

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Water System Service of Evaporator

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Fan Deck Service

Packaged Chiller Service

Chiller Service Company

Chiller Breakdown

Industrial Chiller Service

Chiller Service Company Visit

Chiller Fault Finding & Diagnosis

F-gas Chiller Leak Testing

Chiller Commissioning

Follow this link to purchase BESA pressure testing technical bulletin | Click Here


Chilling plant service showing yellow top recovery cylinder with gauge line and sight glass fitted

Chilling Plant Service

Chilling plant service had been arranged because our customer had been having high pressure problems.

Transducer Required Chilling Plant Service

The 4-20mA transducer needed replacing as it was reading low by a long shot. Therefore, the PLC was not bringing the fans on as it should. The pressure in the high side of the system was getting up to 40 bar. This is because the refrigerant was R410a which has a higher head pressure than other commonly used HFC refrigerants. We ordered the replacement transducer which is fitted with a female fitting.

Chilling Plant Service Leaks

Our engineer concentrated his attention on the high side of the system to start with. Then, he found a leak on a fitting, a leak on the pressure relief valve fitting and a leak on the liquid line near the drier. A sealant was used for leaks on the fittings- they were removed, cleaned and refitted. The leak on the liquid line was re sealed by removing the section of pipe, removing any remaining solder, then the section of pipe was rebrazed.

0161 370 7193

service@maximuschillers.com

Contact Form

Pressure Test

The remaining parts of the system were leak tested then the plant was put on a pressure test to ensure the whole system was leak free. The pressure test was satisfactory and so the evacuation process could be started.

Evacuation Process 

Each of our engineers has a powerful vac pump to speed up the dehydration process. This means that a deep vacuum can often be pulled on the same day, instead of the usual overnight process. The nitrogen and other non condensables were removed quickly and the Torr gauge came down to the pressure where moisture was being removed. At this pressure, any moisture is forced to boil off around the system.

Recharging of the Chilling Plant Being Serviced

In the photo, the plant is being recharged at the end of the work. It is being recharged into the liquid side of the evaporator. All readings were okay when running the system. Further leak tests were then carried out at normal operating pressures.

Related Articles:                                                                                        Chilled Water System EEV Service

Water System Service of Evaporator

Process Chiller Service

HFC Chiller service

Process Chiller Vacuum Service

Chiller Fan Deck Service

Packaged Chiller Service

Chiller Service Company

Chiller Breakdown

Industrial Chiller Service

Chiller Service Company Visit

Chiller Fault Finding & Diagnosis

F-gas Chiller Leak Testing

Chiller Commissioning

Read more about refrigerant reclamation by following this link to Wikipedia | Click Here


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