Chiller Controls Company

Blue ammonia chiller with panel open during chiller controls company visit

Chiller Controls Company

Having an effective chiller controls company saves money! We at Maximus Chillers can repair any fault and upgrade where necessary. Read below to learn more…

Non Condensables

One of the non condensables that is found in a chiller is air. It had got into the system of the chiller in the photo due to a poor repair having been carried out. The end user had tried to save money by using a cheaper company to carry out a change of the suction strainer. They had forgotten to purge the pipework of air, leak test, and then pull a vacuum.

High Subcooling

The ingress of air had caused a ‘high subcooling’ message to appear on the PLC display. The controls work out the subcooling by looking at the pressure transducer reading, in this example it was 14 bar. Then, the onboard comparator understands the pressure/ temperature relationship of the refrigerant which is ammonia. This gave the saturation point temperature of 39°C. Also, the temperature sensor reading on the condenser was 25°C. The 14°C difference between the two temperatures was the subcooling. The parameters in the controls trigger this message if the subcooling is more than 12°C.

Air Purging

Our engineer attended site to carry out air purging according to standard industry guidelines. Our Risk Assessment Method Statement outlined the necessary PPE that was needed when handling this refrigerant. It also outlined the training and certification required by our engineer to handle anhydrous ammonia.

Subcooling Readings

He then ran the system up and checked the subcooling readings again. The condenser pressure was now 11 bar which corresponds to a saturation temperature of 31°C. The condenser temperature was still 25°C, so the subcooling was now 6°C. This was now below the alarm trip out level.

Dalton’s Law of Partial Pressures

This gas law states that all gasses in a pressurised vessel will act as if they are on their own. Therefore, with the air that was in the system, the condenser pressure was 14 bar, then after the air purging it was 11 bar. This means that there was 3 bar of air sat on top of the liquid refrigerant in the condenser. The air was causing a false reading of subcooling and therefore triggering the fault condition.

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Electrical Problems

Another fault message which had occurred during the time we have maintained this machine was oil separator low temperature. The oil separator is the vessel, just visible, to the left of the panel in the photo. This alarm is critical to protect the screw compressor from running with cold oil which will cause an expensive failure.

No Heater Burn Out

The oil separator heater was found to be off despite the cold temperature of the oil. The obvious reason was that it had burned out. The breaker was found to be in the 'on' position and there was no electrical charring visible.

Ohms Checked by Chiller Controls Company

When our engineer checked the ohms readings, they were found to be okay and there was no short to earth.

Run Signal

It was found that the 3 phase contactor was not pulling in to bring the heater on. Therefore, the next thing our engineer checked was weather the controller was sending out the run signal. It was- with 24v coming from the controller and the light being lit on the display. Somewhere in between, there was a problem…

Blown Relay

After consulting the wiring diagram, our engineer traced the fault to a blown relay. This relay provides a step in between from the 24v coming from the controller, to the 240v coil on the oil heater contactor. Rainwater had ingressed through a screw hole in the back of the panel. It had dribbled to the location of the A1 coil terminal on the relay. Here, it had been ‘tracking’ a few volts to earth. This was sufficient to burn out the coil without blowing the fuse. A drying agent suitable for electrical components was used, then the hole was sealed using a compound. There was a spare relay of the same type in the panel, so it was a quick job to swap it out.

Monitoring by Chiller Controls Company

Having done this, the contactor pulled in and the oil heater came on. Balanced amp readings were recorded on all three phases of the heater and the oil started to warm up. The oil separator temperature sensor was monitored for an hour on the controller. When the oil temperature rose to above the trip out level of 46°C, the fault condition automatically reset and the chiller came back on.

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Software Upgrade by Chiller Controls Company 

We had also previously found that the controller software was too finicky- causing a lot of spurious trip outs. Therefore, we decided to design our own software and upload it. This is easy to do because the controller is Bejer Electronics. It is a blank control system which can be used for almost any chiller, or other application. Read below to find out how we did it…

Chiller Controls Company Reliability

We rationalised what the customer needed and developed an upgraded program which was much more reliable. Getting a chiller to settle down and cost the customer less money is what we at Maximus Chillers are all about.

Chiller Controls Company's Test Rig

The controller had been removed from the chiller and wiped of its program. Then, the finished program was uploaded to the controller and a test rig set up. This was to iron out any teething problems before sending it back out into the field.

Laptop Plug In

When our engineer attended site, he fitted the upgraded controller and plugged it into his laptop. All of the program settings can be adjusted on the controller without the need of a laptop by entering the correct passwords for the program level required. However, a laptop has a bigger screen and so multiple readings can simultaneously be monitored. This facilitated the commissioning process.

Chiller Controls Company Testing and Adjustment

The chiller was run tested under various load conditions to check its performance. Also, all the fault conditions were either simulated or tripped out on the chiller. This was so that the program could be put to the test and adjusted accordingly. There were minor problems with fault timers which were adjusted, one at a time, so that no spurious trips would occur.

Completion

After monitoring the chiller for the rest of the day, it was time to talk to the customer about the job and get a signature. This chiller is in South West Wales, so it is a long, but very scenic, drive back for whichever of our engineers attends site. Read more about chiller upgrade.

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Boxed, shell and tube chiller condenser being lifted into a building with a crane

Chiller Condensers

Shell & Tube

The chiller condenser on a 2 MW centrif we look after had deteriorated over a long period of time. We had carried out tube cleaning and noticed that it had been extensively repaired in the past. There were a lot of damaged tubes that had been blanked off. This had reduced the useful surface area for heat exchange to occur. The chiller was experiencing a ‘discharge limiting’ condition which was causing it to back off to 54% capacity.

Air Cooled

Because of the difficulty to remove and replace the condenser from the plant room, the customer had explored the possibility of air cooled condensers. His idea was to fit the discharge and liquid piping up the side of the building and into the plant room. After considering this possibility, we decided to advise him against using air cooled condensers because it would take two, 16 fan ‘V’ types. This would have a footprint too big for the available space. We decided to use a crane to lift out the old condenser, then lift in the new one.

Pump Out

The old condenser was valved off from the rest of the system and the refrigerant was pumped into an 800 kg recovery vessel. This was one of 2 vessels in the plant room that had been there since the chiller was new.

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Lift Out for Chiller Condensers

The pipework was unbolted and the ancillaries removed. When it came to unbolting the condenser, some of the bolts were seized due to a long period of rusting. Some of them came loose by heating them with oxy-acetylene, the others were ground off with an angle grinder. We used a specialist lifting company to shift the condenser from the plant room and out to the lifting bay. They then attached slings to one end, manoeuvred that end of the condenser to the outside of the building, then attached slings to the other end. Rather them than me! Quite a dangerous operation, but it had been assessed when composing their Risk Assessment Method Statement. The condenser was lifted onto the back of an articulated truck and taken to a scrap yard for recycling. There was quite a lot of copper inside- so our customer got quite a good weigh in!

Lift In for Chiller Condensers

The new condenser, in the photo, was kept in its packaging during the lift up, so as to protect it from damage. Once it was in the building and near to the plant room, it was removed from the box and shifted the rest of the way with dollies. There was some difficulty getting it into its final location. This was because the old steelwork had to be cut back with a blow torch to make the new condenser fit. Also, with limited room and no gantry crane, the lifting company had their work cut out to manoeuvre it. Eventually, it was in location and we decided to call it a day.

Adapting the Pipework

This particular condenser was selected because it was similar in dimensions to the old one. The positioning of the refrigerant and water system pipework was similar too. That said, it was not an exact match. We called an industrial plumbing and welding company in to make the changes we needed. They measured up and built adaptors to bolt in between the condenser and the water system pipework. They cut back the new condenser discharge connection and welded a new flange on. This was so it could be bolted onto the existing discharge elbow from the chiller. The liquid pipe connection on the new condenser was in the same location, but came with a different thread. Therefore, this too was cut back and an adaptor fitting was welded into place.

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Ancillaries

The fittings on the new condenser were BSP and the fittings on the chiller were Flare. We carry an extensive range of fittings that go between BSP and Flare. We can go from male to female, female to male, male to male and female to female. We can step up and step down in size too. Using these fittings, we attached the high pressure switch and high pressure transducer. The wires for the liquid and discharge temperature sensors were extended. This was so they could reach the location of the pockets that were built into the new condenser. Then, we used a special heat transfer paste to get a good transmission of heat in between the sensors and the pockets.

F-gas Pressure Test

We then carried out a strength test and a pressure test in accordance with F-gas guidelines. This was witnessed at the beginning and at the end by the customer. A satisfactory outcome was achieved, so on to the next phase of the job…

Dehydration of Chiller Condensers

We needed to dehydrate the system and remove the nitrogen that was used in the pressure test. This is because nitrogen is a non condensable which will affect system performance. Our powerful vacuum pump was set up, then we left it running overnight. A 1.5 Torr vacuum was achieved, which was the same pressure as when the Torr gauge was fitted directly on to the vacuum pump.

Open the Valves and Test

After removing the vacuum pump, the recovered refrigerant was pumped back in, then the discharge and liquid valves were opened back up. Then, our engineer had a good look round for leaks. I know it had just been pressure tested, but we think it’s always a good idea to check again. This done, the water system pumps were started and the water temperature showed at 23°C on the controller. The set point for the chilled water was 6°C so this warm water was helpful as it gave us plenty of load to carry out the testing. The chiller went through a timer and then started up. It loaded steadily up to 100% with no dramatics- splendid!

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

For further reading on chillers and the chiller maintenance schedule- visit Better Bricks | Click Here


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.

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

Superheat

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

Refrigerant Shortage

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

Expansion Valve Failure

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

Thermostatic Expansion Valves

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

Electronic Expansion Valves

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

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Subcooling

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

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

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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.

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Water System Temperature

The chiller should be:

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

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

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

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

Small Chiller Maintenance Checklist

Low Pressure

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

Breakers

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

Condenser

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

High Pressure Switch

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

Large Chiller Maintenance Checklist

Suction

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

Discharge

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

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Chiller Remote Monitoring

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

Parts

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

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

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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


Yellow oil drums, ammonia refrigerant cylinders and flammable flushing agent of chiller supplier

Chiller Parts Supplier

Chiller Parts Supplier of Compressors

Centrifugal

As a chiller parts supplier, all kinds of centrifugal compressors are remanufactured in our workshop. With an overhead gantry crane and specialist equipment to hand- Maximus Chillers completes the picture. We have a lift and shift team who are skilled at getting the compressor out of the most awkward locations. A variety of lifting equipment is used, including 3 phase electric hoists and trollies. Our team do this kind of work all the time, so they are accustomed to overcoming all the difficulties and obstacles.

Screw

Screw compressors are remanufactured on the bench. With compressed air and bearing tools- our skilled technicians are seasoned in high tolerance measurements. The bearing clearance and shaft run out are accurately measured and adjusted. This means that the useful life of the compressor is extended, often to beyond the lifespan of the chiller.

Scroll

We have a range of off the shelf Copeland compressors for a fast lead time on process chiller repairs. These can be sent to site on the day using our fast door to door supply chain. We have all the sizes of compressor available. The pipework and mountings can be adapted too. This means that if your compressor is a different make with a longer lead time- our compressor will be fitted and adapted to your machine- fast!

Chiller Parts Supplier of Condensers

Air Cooled

When the condenser on an air cooled chiller is in poor condition- our site survey team will attend to measure up for a new bespoke condenser. This is done free of charge and ensures that the new condenser will fit easily into the old chiller. The exact subcooling requirement of the old condenser is taken into account which is duplicated on to the new condenser. This means a like for like swap can take place even when the old condenser is obsolete.

Shell and Tube

This type of condenser is used on water cooled chillers. It is protected from contaminants by a strainer on the water system. We have these condensers built to order by our bespoke manufacturer. They are shipped to site on an overnight delivery, so we can get straight down to work in the morning. We therefore minimise downtime in the swap out of this part.

Chiller Parts Supplier of Evaporators

Shell and tube are the most popular type of evaporator for large chillers. The low temperature refrigerant is on the outside of the tubes in liquid form. The water is pumped through the tubes, releasing heat from the process and into the refrigerant. This is latent heat as the liquid refrigerant boils off into a vapour. Where the heat exchange does not greatly improve after cleaning, we recommend replacing this part.

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Vibration Eliminators

We have all of the sizes of anacondas on the shelf in our stores. This saves on the delivery time to site when your process is off due to the chiller. Maximus Chillers will get you up and running- fast! We can also fit flexible vibration hoses which achieve the same result as anacondas. Whereas two anacondas are fitted vertically and horizontally, only one, long vibration hose is needed.

Chiller Parts Supplier of Flushing Agent

When things go wrong, we stock a solvent based flushing agent which is blown through the system using nitrogen. The waste product is caught on the far end in drums that come with the kit. This is then returned to the suppliers for recycling.

Refrigerant Economizers

These are another term for a subcooler. If the refrigerant is further subcooled after the condenser- the system will run more efficiently. This part usually takes the form of a plate heat exchanger with an expansion valve providing the refrigeration effect needed to further subcool the remaining liquid.

Chiller Parts Supplier of Pressure Transducers

We can make temporary repairs to faulty pressure transducers using our test equipment. This will keep your plant running while the part arrives on site. Then we can get your chiller up and running with the correct readings in the controls. This will assist your onsite maintenance engineers in giving us useful readings when we are in communications over the phone.

Chiller Parts Supplier of Ammonia and HFC Refrigerant

A full selection of refrigerants are available including: anhydrous ammonia, R407c, R134a and R410a. These refrigerants come in small 12kg, midi 26kg, large 56kg and bomb 800kg sizes. Our vehicles are equipped with tail lifts and lifting gear to facilitate delivery. We can therefore arrange the delivery and collection of refrigerant at your site, free of charge, anywhere in the UK. For our overseas customers, we arrange the transportation from the local suppliers.

Chiller Parts Supplier of Oil

Low, medium and high viscosity oils in 5ltr cans and 20ltr drums are ready for shipping from our storage area. It is critical to select the correct grade of compressor oil as bearing wear and reduced service life will result. We take regular samples of this oil to see if things are starting to go wrong in the compressor. We can then nip these problems in the bud, giving you dramatic savings.

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

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6 large air cooled chiller condensers maintained with 12 fans each

Air Cooled Chiller Condenser Maintenance

The photo is showing air cooled chiller condenser maintenance being carried out by Maximus Chillers. 6 water cooled chillers are located in the plant room below. They are 750 kw single screw compressors with a control panel located to the side of each. On this visit, the emphasis was to carry out a thorough maintenance of the condensers.

Fan Speed Controllers

The refrigerant for the systems is R134a, so to allow for the saturation of the refrigerant, 8 bar is the head pressure set point. This pressure corresponds to the desired condenser temperature of 36°C. Subcooling of 6°C to 8°C is achieved during the nominal operation of the plant. Each fan speed controller runs the 12 condenser fans together. Other condenser designs where fans bang on forwards and backwards cause vibrations resulting in reoccurring leaks on the condenser. Chiller No. 2 had tripped during a 'discharge override' system message. On inspection of No. 2 condenser- the fans speed inverter had tripped on 'over temperature' alarm. The panel fan, which is the kind to cool computers, was found to be still trying to run but seized. This failure had caused the alarm on the inverter. The panel fan was replaced from the stock of parts in the onsite stores. The chiller was reset and a detailed Tick Sheet was completed noting the occurrence of this fault on arrival.

Air Cooled Chiller Condenser Maintenance Cleaning

Because of the large size of the plant, the customer had installed a fireman’s hose for the cleaning of the condensers. This is located in the free space beneath the condensers. It is fitted to a portable buggy so it can be moved under each condenser. Setting the nozzle to the correct attitude, our engineer moved the buggy sideways, so as to rinse the condenser in the direction of the fins. The condenser was relatively clean as the onsite maintenance engineers carry out this task as part of their monthly schedule.

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Design Considerations for Air Cooled Chiller Condenser Maintenance

The kind of condenser in this article is:

Multiple Row Tubing

3 Rows

It has tubing of ½” diameter which is 3 rows deep. Each pass starts at the discharge header which is at the inlet to the condenser, goes down to the far end, through a condenser end turn, back to the discharge end, through another condenser end turn and back again to the liquid pipe end. The heat removed from the condenser, per kg of refrigerant, is the heat content of the vapour as it leaves the compressor, minus the heat remaining in the liquid at the end of the condenser.

6 Rows

Some condenser designs are up to 6 rows deep. This allows a small footprint of space where there is not much room for the location of the chiller. The downside to this, is that the chiller engineer can often struggle to locate the exact location of a leak when it is deep into the coil. If a condenser is too small, it will cause a higher head pressure and reduce the life of the compressor. We can arrange the lift out and repair of deep row condensers in our workshop.

Finned

This condenser has aluminium fins which are pressed around the copper tubing. This increases the surface area of the condenser heat exchange medium and so increases the dissipation of heat. The same amount of heat delivered to a condenser from the compressor must also be rapidly removed. For this condition to be reached, enough head pressure will need to be built up so that the condenser temperature is at least 15°C above the ambient. This is why the same chiller can be picked up and shipped to the Middle East and still work. It will just run at a higher discharge pressure/ temperature. There will, however, be a loss in the coefficient of performance as the higher pressures will result in more electricity in, versus the same amount of refrigeration effect out.

Forced Convection Type

The fans mounted on the ducting provide this forced convection. The air is sucked through the bottom of the condenser, across the 3 rows of tubes, along the fins and up through the fans. The air flow is stable as it enters the fins so good heat transfer is achieved. As it leaves the fins at the top, there is lower heat transfer as the air is turbulent.

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Fan Replacement during Air Cooled Chiller Condenser Maintenance

Spare fans are available onsite for replacement when individual fans fail. As mentioned above, these condensers are controlled with FSC's which reduce the occurrence of leaks. As well as this, fan speed controllers increase the lifespan of the fans. Because all of the fans run together, they speed up and slow down steadily. When high pressure control switches are used, they are set at different pressures. This means that some of the fans never come on until the head pressure is too high. This is usually due to a blocked condenser, failed fans or a high ambient. Because the fans have not come on for a long time, they are often seized or have suffered water ingress from the rain. An onsite maintenance engineer is available to help with the lift out and lift in of the replacement fans.

Pressure Relief Valves

Each of these condensers is fitted with a pressure relief valve (PRV) It is fitted into the discharge pipe on the inlet to the condenser. This is so that if the fans and the HP switch were to fail, the dangerous levels of pressure in the system would be vented. It is unlikely, however, that the HP switch would fail as this is a very reliable part. A PRV being fitted is often the requirement of insurance companies. The testing or replacement being arranged at scheduled intervals.

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

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An R407c chiller condenser retrofit lifting operation outside in the compound

R407c Chiller Condenser Retrofitting

We recently undertook the job to carry out bespoke R407c chiller condenser retrofitting in the North West.

Rusted and Corroded Condenser

The old condenser looked alright on the surface- the fins were in good condition. The condenser was 18 years old, however, so when an attempt to repair a leak was carried out- the condenser leaked further along. This is because of the warming of rusted and corroded copper with an oxy-acetylene torch.

R407c Chiller 'V' Condenser Retrofitting

We arrived on site to measure up for the job. The ‘V’ condenser was built to order. We manufactured an exact replica to the same specifications and sizes of the old one. The operating pressures and high pressure cut out limit were taken into account in the design and the use of materials.

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Lift Out of the R407c Chiller Condenser being Retrofitted

On the day of the lift and shift we isolated the panel and checked it was dead, then we removed the panel and laid it on its front. This was to access the rivets behind the panel. These rivets, the ones on the other end of the chiller and around the lid were removed using a tool. The fans were disconnected and removed to make the lid lighter to lift off. Then, we attached slings to the chiller condenser and lifted both halves of the 'V' out.

Lift In

This part we did not want to get wrong as the condenser was brand new and did not have a mark on it. A reverse of the removal- it fitted perfectly just the same as the old one. With the lid lifted back on and the fans in- time for brazing then the pressure test.

Pressure Test, Dehydration and Recharge

The pressure test was satisfactory so our engineer put the system on vac for dehydration purposes and the removal of non condensables. After a deep vacuum was achieved the system was recharged and run tested. No issues were found.

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Chilled water system repair of condenser to a silver chiller with blue compressors

Chilled Water System Condenser Repair

Chilled Water System Condenser Beyond Repair

The repair of the condenser was required on this chilled water system because the previous company had been chasing leaks round in a circle. Therefore, the customer had decided to buy a new condenser. This was our first job with a new contract, so we wanted to make a good impression.

Condenser Removal

There was no refrigerant in the system, so our engineer cut the discharge and liquid line to the condenser. He then removed the rivets so the frame could be taken apart. Lifting equipment was fitted to the old condenser to aid the removal. Then, slings were fitted and a forklift truck removed the old condenser.

Condenser Replacement

Our engineer supervised the condenser replacement. He found that the new condenser did not fit correctly. The new condenser was 5mm thicker than the old one. It was decided to lift it back out and angle grind the frame to make more room. Once this was completed, the new condenser fitted correctly and was bolted in place.

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Pipework Repair

The pipework had to be repaired and brazed in. Then, the standard practice of a pressure test to ensure the integrity of the system.

The Evacuation Process during Chilled Water System Condenser Repair

Having passed the pressure test, our engineer set up the vac pump and started the evacuation process. This is to dehydrate the system by pulling a vacuum of less than 2 Torr. Any moisture in the system will boil away and leave the system dry.

Recharge and Test Operation

The refrigerant is R410a. Our engineer put around half the charge in, then trimmed the remaining charge according to the superheat and subcooling values. He monitored the system for the rest of the day- looking for leaks as the plant was at operating pressures of 30 Bar. All was well, so the customer signed off the paperwork as he was pleased with the capability of our engineer.

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