Improve Chiller Efficiency

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

Improve Chiller Efficiency

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

News Article No.18

Improve Chiller Efficiency with a Clean Condenser

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

Improve Chiller Efficiency by Removing Evaporator Thermal Insulation 

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

Blocked Strainer

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

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Improve Chiller Efficiency with Correct Refrigerant Charge

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

Refrigerant Leak Repairs

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

F-gas Register

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

Blocked Pump Fan

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

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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


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.

Related Articles:
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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 an electrical transformer on Wikipedia


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!

Related Articles:
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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


Brazing equipment box and vibration eliminators during packaged chiller service

Packaged Chiller Service

Packaged chiller service due to a refrigerant leak, resulting in a trip out. This visit was to identify the leak and get the plant back online.

Leak Testing During Packaged Chiller Service

Nitrogen was added to the system to aid in the identification of the leak. All parts of the system were checked, including the removal of lagging around the couplings onto the evaporator. The leak was found on a poor quality ‘eliminator’ which had rubbed through on the evaporator.

Vibration Eliminators

We decided to fit high quality vibration eliminators- see picture. These are fitted one in the horizontal position and the other in the vertical. They absorb both directions of vibration, then they are clamped to the chiller frame.

Brazing During Packaged Chiller Service

The pipework brazing was carried out with all combustible materials being removed from the work location. A permit to work was opened with our engineer as the responsible person. A half hour fire watch was carried out on completion of works.

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Pressure Test During Packaged Chiller Service

The pressure testing was carried out using nitrogen. As nitrogen is an inert gas, it will not cause other potential risks to the chiller and other personnel. The pressure test was a pass, so the next phase of the job could be carried out…

Vacuum Pump

Each engineer carries a 10 cfm vacuum pump. This high capacity ensures a fast vacuum. The Torr gauge was fitted to the system and 2 Torr was pulled.

Refrigerant Saturation

In the cylinder, the saturation of R407c is 7 bar at 11°C The refrigerant in the cylinder is in its liquid phase with vapour on top.

Subcooling

On run testing the chiller, the subcooling value was found to be nominal at the industry standard level.

Superheat

The superheat was adjusted, little by little, with the charging of the refrigerant until a good value was achieved. This was tested across all loading conditions for the rest of the visit.

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Water System Service of Evaporator

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Process Chiller Vacuum Service

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Industrial Chiller Service

Chiller Service Company Visit

Chiller Fault Finding & Diagnosis

Read more about reducing refrigerant leaks at the Institute of Refrigeration


Green Bitzer compressor being vacuumed during HFC chiller service

HFC Chiller Service

The HFC chiller being serviced in the photo is 600kw. It consists of two systems with a large Bitzer compressor for each system. It has a bespoke Micro Control System front end to run the machine and stop it should there be a fault condition. The chiller had been reported by the customer to have tripped out on a low pressure fault.

HFC Chiller Diagnosis Service

The readings of superheat and subcooling are available in the controller. This removes the need to fit instrumentation carried by our engineers. The process of diagnosis was therefore speeded up. The result being that the chiller was found to be running short of refrigerant.

Return Visit to Decant the Refrigerant

A Quote was submitted to the customer for approval. Once the Order was raised, a convenient time was arranged to return to site and carry out the service visit. The remaining charge of refrigerant was decanted into our recovery vessels with one of our fast pump out units which are carried by each of our engineers.

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Looking Around the Pipework for a Leak

Nitrogen, an inert gas, was introduced into the system to assist in the location of the leak. The leak was quickly found on one of the end turns of the condenser.

Brazing and Pressure Testing

Our engineer made good the leak using his brazing torch. Then, the integrity of the system was proven to industry standards with a system pressure test.

The Evacuation Process for HFC Chiller Service

The picture shows a 10 cfm (cubic feet per minute) vacuum pump being used to dehydrate the system during the visit. Each of our engineers carries a vacuum pump of this capacity as it speeds up the process. One refrigerant hose being fitted to the discharge pipe and another, smaller hose being fitted to the suction pipe. The system being drawn down to a deep vacuum.

Recharge and Run Testing

After the chiller had been recharged with some of the charge of the refrigerant R134a, the remaining refrigerant was charged in its liquid phase, away from the compressor, until the superheat and subcooling values were within industry limits. A large amount of load was available to the chiller as it feeds an air blown film plastic manufacturing facility.

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Chiller Breakdown

Industrial Chiller Service

Chiller Service Company Visit

Chiller Fault Finding & Diagnosis

F-gas Chiller Leak Testing

Chiller Commissioning

Air Cooled Chiller Condenser Testing

Read more about a film blowing machine on Wikipedia


Water chiller service of evaporator showing lagging removed and blue compressor

Water Chiller Service of Evaporator

Not often does a water chiller service of evaporator fault occur. The evaporator can freeze up and burst the tubes inside the shell. This fault involved the shell itself bursting. On close inspection- the shell was made out of thin steel- not the usual heavy rolled steel. It looked like the near end on the photo had sagged down- causing the evaporator shell to buckle.

Replacement of Evaporator

This option would be expensive due to the cost of the evaporator. It would be a difficult visit because of access issues. The builders decided to site the chillers round the back of the building, this makes them very difficult to service. Our lift and shift guys would be needed to get the old chiller evaporator out and the new one in. There is a difficult corner to get round where the evaporator would have to be tilted up to get it round. Also, a fence wound have to be taken down around the chillers. Of course, security is an issue but so is access to the chillers.

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Water Chiller Service of Evaporator using Silver Solder

Because of the above, it was decided by the customer that we would fix the leak using silver solder. The Risk Assessment Method Statement allowed for the job to be carried out with a half hour fire watch. The oxy-acetylene lines were leak tested prior to the job. Both leaks were soldered up but despite the evaporator being drained down, there was still water and steam trying to get out. Not the best soldering resulted- but it held.

Water Chiller Service of Evaporator Paintwork

Because the chillers are outside, the paintwork is essential- poor paintwork will reduce its life. After preparing the surface, specialist paint was applied so as to protect the evaporator for the future.

Lagging

The purpose of lagging is to reduce heat gain from the environment and provide protection from the elements. Therefore, the lagging was reinstated after the job.

Related Articles:
Chilling Plant Service

Chilled Water System EEV Service

Process Chiller Service

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Service Company

Chiller Breakdown

Industrial Chiller Service

Chiller Service Company Visit

Chiller Fault Finding & Diagnosis

F-gas Chiller Leak Testing

Chiller Commissioning

See the Institute of Refrigeration Evaporator Efficiency

 


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