Preventative Chiller Maintenance

Carel controller showing R134a refrigerant readings during preventative chiller maintenance

Preventative Chiller Maintenance

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

News Article No.9

Chiller Control Panels

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

Programmable Logic Controller

Alarm History

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

Settings and Timers

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

Compressor Run Hours

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

Preventative Chiller Maintenance of Electrical Safety Devices

Fuses

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

Circuit Breakers

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

Residual Current Device

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

Preventative Chiller Maintenance of Refrigerant Safety Switches

High Pressure Switches

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

Low Pressure Switches

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

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Coefficient of Performance during Preventative Chiller Maintenance

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

Latent Heat 

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

System Efficiency

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

Superheat

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

Subcooling

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

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Preventative Chiller Maintenance and Condenser Fans 

Basic Design

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

Refrigerant Leaks

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

Preventative Chiller Maintenance with Fan Speed Controllers 

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

Axial Fans

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

Radial Fans

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

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Preventative Chiller Maintenance and R134a Refrigerant

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

Characteristics

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

Centrifugal Drop In

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

Global Warming Potential

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

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Chilling Plant Maintenance

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

To watch a video about chiller efficiency and the coefficient of performance | Click Here


Chilling plant maintenance of grey machines with red warning signs

Chilling Plant Maintenance

We at Maximus Chillers carry out chilling plant maintenance in factories and facilities around the UK and overseas.

HFC Refrigerants

HFC (hydrofluorocarbon) chiller refrigerants were developed to be chlorine free. For a while they were seen to be the great new thing until the GWP (global warming potential) of the refrigerants became more of a concern. The release of these refrigerants from leaking systems dramatically increases the green house effect and so trapping more heat in the atmosphere. For this reason, F-gas regulations are phasing them down to 21% by 2030. Because of the 650kg charge in the chillers in the photo, we carry out leak testing at one month intervals. Where a leak is identified with this refrigerant, the system can be pumped out using the push/ pull method. There are no refrigerant system shut off valves available to allow the systems to be pumped down.

Chilling Plant Maintenance using Leak Detectors

We employ HFC refrigerant leak detectors to identify any leaks around the system. On systems of this size, there may be more than one leak, with a large leak alerting the attention of the engineer and the smaller leaks found subsequently. Our leak detectors are sent off periodically to be calibrated with the internal replaceable components upgraded as necessary.

Static Leak Detectors

Static leak detectors are available for each machine to catch any leaks as soon as they happen- before the one month intervals. This reduces the amount of refrigerant leaking to atmosphere and so adding to global warming. These leak detectors are bump tested on each visit to ensure reliability with replacements available on site, should one of them fail.

Chilling Plant Maintenance for One World

The above measures are essential with this kind of refrigerant in the interests of the environment. Basic checks now, protect the future of the planet. We only have one world, so we need to look after it as best we can. You can rest assured that you are in safe hands with how we handle this range of refrigerants.

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Shell and Tube Chiller Condensers

During the maintenance, we assess the subcooling values under part and full load to diagnose the efficiency of the shell and tube condensers. This kind of condenser is very popular with larger chillers in the UK. They are not sensitive to different weather conditions as the heat rejected into the condenser water system is pumped into the cooling towers outside of the plant room.

Chilling Plant Maintenance of Copper Pipework

The nest of pipes inside the shell are constructed using copper. This is because of the excellent heat transferring properties of this metal. On other sites where the refrigerant is ammonia for example, stainless steel is used as ammonia corrodes copper and most other metals and alloys. Thorough maintenance of the pipework is carried out on each visit.

Water System Maintenance

The water loop is inspected at various test points around the system with our range of test equipment. Where there are readings that are starting to go beyond nominal conditions, we carry out adjustment to bring them back into line. If the water system is behaving abnormally, this will in turn affect the efficiency of the condenser. In extreme circumstances, a system failure can occur causing a potential loss of production. Effective maintenance from Maximus Chillers has evolved over time to prevent this from happening in the first place. Each time we encounter a new issue, a thorough investigative process is carried out, the solution is arrived at and this is added into the routine.

Air Bleed Ports during Chilling Plant Maintenance

Air can be pulled into the condenser from the cooling towers outside. This can sit on top of the water in the condenser and so prevent the heat exchange of latent heat from the refrigerant and into the water. An air lock in the condenser amounts to that portion of the heat exchanger from not being in use. This dramatically affects the efficiency of the plant. We carry out checks to each condenser and bleed any air on each visit to ensure the best running conditions of the plant.

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Refrigerant System Standing Pressure

One of the ways to assess the condition of the refrigerant is the standing pressure. Only during factory shut down are all the chillers off for long enough for the system pressures to stabilize and so have a consistent standing pressure around the system. The pressure readings can be taken and added into our software to determine the composition and purity of the refrigerant and the presence of non condensables. Where the refrigerant is found to be in poor condition, maintenance can be arranged to rectify the issue.

Coefficient of Performance

The coefficient of performance is the cooling effect compared to the amount of electricity used. In an inefficient system, a small amount of cooling is achieved relative to a large amount of electricity used. In this age of environmental concerns, we carry out extensive measures and adjustments to improve the COP. Not only is an efficient plant cheaper to run, it is better for the environment too.

Control Panels

The control panels for the chillers in the photo are defunct. That is to say- the component parts are no longer manufactured. I am sure there is the odd circuit board rolling around on a shelf somewhere, but we fit state of the art controls. Our supplier builds bespoke panels exactly suited to each particular machine. They are plug and play with associated sensors, transducers and vane loading actuators supplied. The panel is fixed next to the chiller, wired in and ready to go. All settings come as default, so just the odd one needs to be modified. The panel can be easily integrated into the existing remote start stop and variable speed drives.

Related Articles:
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Process Chiller Maintenance Visit

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Air Cooled Chiller Condenser Maintenance

Glycol Chiller Maintenance

Preventative Chiller Maintenance

To read more about shell and tube chiller condensers hit the Tag at the top of the page.

For further reading on Hydrofluorocarbon Refrigerants | Click Here


7 large air cooled chiller condensers maintained with 12 fans each

Air Cooled Chiller Condenser Maintenance

Air cooled chiller condenser maintenance at Maximus Chillers. The condensers in the picture are a row of 6. These are remote from a row of 6 chillers, located in a plant room in the building below. The chillers are 750 kw single screw compressors with a control panel located to the side of each. On this visit, the emphasis of the maintenance was scheduled as being to 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°. Subcooling of 6° to 8° 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.

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Air Cooled Chiller Condenser Wash Down Maintenance

Because of the large size of the plant, the customer had installed a fireman’s hose for the wash down of the condensers during air cooled chiller maintenance. 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 on site maintenance engineers carry this task out as part of their scheduled maintenance.

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

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Preventative Chiller Maintenance

Read more about HVAC air coils on Wikipedia | Click Here


Chiller refurbishment company electronic components in electrical panel

Chiller Refurbishment Company

Choosing a chiller refurbishment company is cost effective because the main cost of a large chiller is mostly in the fixed plant. That is to say: the two main heat exchangers and the compressor. Therefore, this is the most environmentally friendly option as the carbon footprint of building new plant is very high. This is not mentioned when you purchase a new chiller. With chiller controls replacement, this kind of plant can last for 50 years. One of our competitors has been carrying this out to a chiller that dates back to the 1970s and is still in service!

Chiller Evaporator Refurbishment Company

Refurbishment of broken tubes can be performed to beyond manufacturer's recommendations. Larger scale replacement of the tubes can be carried out giving the same lifespan of the original tubes. This is a major overhaul at a fraction of the cost of replacing the chiller.

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Chiller Compressor

We strip the chiller compressor down in our workshop. It is made from heavy castings so will last a very long time. We provide a 12 month warranty on all our chiller compressors. Read More about centrifugal compressor remanufacturing on our web page.

Chiller Controls

State of the art controls can be fitted. The controls that come with the chiller are made 'in house' so they are often prone to spurious trip outs. These trip outs can cause a loss in production. A control panel, designed specifically for that chiller comes ready built. All you have to do, is wire in the various sensors and transducers. The run signal, compressor soft start, remote loading and monitoring can be easily integrated. Simple and easy solutions to big problems are what we do!

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

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Read more about the chiller controls we fit to existing chillers.


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