Chiller Efficiency

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

Chiller Efficiency

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

News Article No.18

A Blocked Condenser Decreases Chiller Efficiency

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

Evaporator Thermal Insulation Decreases Chiller Efficiency

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

Blocked Strainer

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

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Refrigerant Shortage Decreases Chiller Efficiency

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

Refrigerant Leak Repairs

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

F-gas Register

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

Blocked Pump Fan

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

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Waste of Money

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

Maintenance Visits Improve Chiller Efficiency

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

Mobile Workshop

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

Kilowatt Hour Meters

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

Scheduled Chiller Maintenance

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

Technical Support Desk

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

Related Articles:
Air Cooled Chiller Condenser Testing

Shell & Tube Chiller Evaporator Maintenance

F-gas Chiller Leak Testing

Planned Preventative Chiller Maintenance

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

Read more about how to improve chiller efficiency on The Engineering Mindset | Click Here


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

Chiller Types

In this article we will be exploring the various chiller types. They can be categorised according to: how the condenser is cooled, weather they use vapour compression or absorption and the required chilled water temperature…

News Article No.17

Air Cooled Chiller Types

This type of chiller uses the ambient air to cool the refrigerant in the condenser. Fans suck the air through the condenser fins and so exchanging heat energy from the refrigerant and into the air. They are particularly popular in the UK due to the low ambient temperatures. They are also used in the Middle East, but the higher ambient means that they run less efficiently. Read more by following this link Click Here

Water Cooled Chiller Types

This type of chiller uses a shell and tube condenser to remove the heat energy from the refrigerant. The refrigerant condenses from a gas and into a liquid on one side of the tubes. On the other side of the tubes, condenser cooling water is being pumped through and so absorbing latent heat from the refrigerant. The water flows up to a cooling tower where it cascades down through trays and into the sump. In the opposite direction, air is blown up through the cooling tower and so creating the required heat exchange. The cooled condenser water is then pumped back to the chiller. This kind of system is more often used with large capacity chillers. Read more by following this link Click Here

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Vapour Compression

Vapour compression is the most popular kind of chiller. An electric motor drives a compressor. The refrigerant is then discharged into the condenser where the heat energy is rejected from the refrigerant as it cools down into a liquid. It goes through an expansion valve where it drops in pressure and temperature. Then, the refrigerant goes into the evaporator where it boils off absorbing latent heat from the water being chilled. The refrigerant is then sucked back into the compressor. This is called The Basic Refrigeration Cycle and you can read about it in detail by following this link Click Here

HFC Chillers

HFC chiller refrigerants, such as, R407c were developed to replace refrigerants which contained chlorine. This is because chlorine was found to have caused a hole in the ozone layer. The downside to HFC refrigerants is that they have a high Global Warming Potential. That is to say that when they find their way into the atmosphere due to refrigerant leaks, their heat trapping qualities add to the greenhouse effect.

Ammonia Chillers

The photo is of two ammonia chillers with air cooled condensers on top. A steel braided refrigerant charging hose can be seen coming into the foreground of the photo. This refrigerant has a zero global warming potential and so is environmentally friendly. The downside to this refrigerant is that it is highly toxic and corrosive. Therefore, special procedures, equipment and training is required to handle it. Read more by following this link Click Here

Propane Chillers

Propane didn’t really catch on in the UK due to the higher initial cost of the chiller. It is, however, popular on the continent in countries such as Italy. The downside to this refrigerant is that it is highly flammable. Intrinsically safe equipment is required to handle the refrigerant and so aiding with a spark free environment. Read more by following this link Click Here

Absorption Chillers

This kind of chiller uses a heat source rather than electricity to drive the cooling process. It employs a chemical reaction between two substances, such as, lithium bromide and water. To read about these chillers in detail Click Here This type of chiller is a lot less efficient than vapour compression systems. The coefficient of performance is usually around 0.5, were as with a HFC chiller it is usually upwards of 4. Therefore, they are most often used where there is a surplus of waste heat being produced by a process, such as, in a power station.

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High Temperature Chiller Types

Laser cutters use a chiller which operates with a high temperature set point of around 25°C. The laser head and the oscillator need to be cooled to a very close deadband of usually around 0.2°C. If there is a problem with the chiller, the controls shut the laser cuter down to prevent expensive failures from occurring. Read more by following this link Click Here

Medium Temperature Chiller Types

Most chillers operate at this temperature which is used for a variety of applications including…

The Cooling of Buildings

The chilled water set point is usually around 6°C. Large capacity chillers are used which supply chilled water to the building. A plant room is located near to the chillers where a pump discharges into the chillers. The water system pressure is maintained using a pressurisation unit. A different pump is used to supply fan coils around the building. The fans blow air across the chilled coils and so cooling the spaces in the building. This heat exchange warms the chilled water which returns back to the chillers.

The Plastics Industry

Two popular ways of forming plastic are by using: plastic extrusion moulding machines and plastic injection moulding machines. Plastic granules or powder is melted down and forced through a die or into a mould. Chilled water is then used to control the cooling of the newly formed plastic to below its freezing point. Small chillers are used next to each of the plastic forming machines. Alternatively, large, centralised chillers are used to provide chilled water to the whole factory.

Low Temperature Chiller Types

Breweries are a good example of the use of low temperature chillers. The setpoint is often around -5°C with glycol being added into the water to prevent it from freezing. The water/ glycol solution is pumped around the jackets of stainless steel vats which are used to brew the beer. The fermentation process created by the yeast is temperature critical and so is controlled by the chilled water. Read more by following this link Click Here

Related Articles:
Air Cooled Chiller Maintenance

Chiller Condensers

Industrial Refrigeration Ammonia

Glycol Chiller Maintenance

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

How Does A Chiller Work

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

The Basic Refrigeration Cycle

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

Sensible heat

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

Example

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

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Latent Heat

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

Example

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

How does a chiller work on a PH diagram

The Pressure Temperature Relationship

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

Higher Pressure

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

Lower Pressure

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

Refrigerant

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

Refrigerant Saturation Point

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

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How Does A Chiller Evaporator Work

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

How Does A Chiller Compressor Work

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

How Does A Chiller Condenser Work

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

How Does A Chiller Expansion Valve Work

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

How Does A Chiller Set Point Work

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

Related Articles:
Shell & Tube Chiller Evaporator Maintenance

Chiller Compressors

Chiller Condensers

Chilled Water System EEV Service

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

Read more about vapour compression refrigeration on Wikipedia | Click Here

 


Chiller commissioning of a large white chiller with the pipework still disconnected to the buffer tank

Chiller Commissioning

Chiller commissioning is carried out to resolve any issues and get a machine running with optimum efficiency. The first three days are the most important part of a chiller’s life. This is because a chiller will carry along with it any problems that were not resolved at the start.

News Article No.15

New Chiller Commissioning

We at Maximus Chillers are the approved supplier for various manufacturers as their first choice to commission their new chillers. This is because we have earned a reputation within our industry for the capability to do anything- this is just part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere.

Used Chiller Commissioning

Our customers are concerned with lowering their carbon footprint and reducing the environmental impact made by cooling systems. One of the ways they do this is by purchasing used chillers which still have 10 years of life in them. This means that there is a dramatic saving in the carbon emissions that would have been released during the manufacture of new chillers. Used chillers often come from factories that have been re located. They also come with a full service history.

Chiller Commissioning on Site

The chiller in the photo is about to have the commissioning process carried out. All that is left to do is for the onsite engineers to fit the Inlet and Outlet pipes to the evaporator. Then, fit the water system pumps and other water system components.

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Chiller Commissioning Day 1

A cup of coffee and a good look round before staring anything. There were still a few nuts, bolts and washers left lying around by the onsite engineers, so a good opportunity for some house husbandry. This done, our engineer switched the main power supply on to the chiller…

Flow Fail

The machine went immediately into the flow fail fault. Then, he powered up the chiller pump set and the process pumps that feed the factory. The flow fail alarm cleared- so that was the flow switch ticked on our detailed Commissioning Sheet.

Line Voltage

He then checked the 415v power supply to the chiller which gave a good read back and balanced phases. Then, he checked the volts, amps and rotation on the pumps which also gave a good read back.

Buffer Tank Level

The buffer tank auto fill sensors had been positioned incorrectly. He adjusted them to the correct level, the mains water auto fill started and the tank filled to its set level.

Water System Leak

A small leak was found in between the outlet pipe from the buffer tank and the inlet of the process water pump. Our engineer rang one of the onsite engineers who arrived to tighten the connection.

Tighten Wiring

There hadn’t been an opportunity to tighten the wiring for some time as this chiller had been in continuous production in another part of the factory. Each wire around the chiller was tightened including the panel, the fan decks and the motor terminals on the Bitzer screw compressors.

Chiller Commissioning Day 2

The application and set point were different for the process at the new location of the chiller. Therefore, the controller was interrogated using a password to access the parameters. The parameters were modified, one at a time, until they came in line with the customer’s requirements.

Remote Controller

A remote controller had been fitted in the factory near to where the process workers carry out their duties. This was so that they do not have to walk outside to monitor the running of the chiller when they are also monitoring the process. Simultaneous monitoring of chiller loading, faults and water temperature is needed, as well as the monitoring of the process temperatures and production rates. The production rate can be slowed down if the chiller is in a fault condition. This is so as to balance against the process chilled water temperature.

Display Fault

A fault was showing on the remote controller display that was not showing on the chiller controller. After following the diagnosis and consulting the wiring diagram, the fault was traced to three wires that had been connected in the wrong order- an easy fault to rectify.

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Chiller Commissioning Day 3

Having sorted out the above, it was time to run the chiller up in anger…
A time was selected for start up when maximum load was available from the factory. This was to ensure that the machine could cope and to show up any problems.

System 1

This system started at 25% capacity and loaded up through each stage until it reached 100%.

Oil Level

A low oil level was recorded on the oil sight glass. Therefore, our engineer carefully monitored the compressor amps, temperatures and pressures to see if the compressor was starting to leave its nominal operating conditions. Bitzer screws are a high quality and very robust compressor, so the readings stayed good until the oil level returned.

System 2

This system then started and loaded steadily to 100%. All of the chiller readings were taken and were found to be within standard industry guidelines.

Load Matched

As the chiller started to near the set point, both compressors started to unload to match the load. The load can vary according to what the process engineers are doing at the time, so proving the compressor loading was critical to the efficient running of the plant.

Scheduled Maintenance

With the Commissioning Sheet filed in the cabinet, the next scheduled maintenance visit was talked through with the customer. There are 3 minor visits and 1 major visit during the year. The major visit is scheduled to take place during the winter. This is because there is more time available to carry out the periodic oil and filter changes.

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Chilling Plant Service

Chilled Water System EEV Service

Water System Service of Evaporator

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Breakdown

F-gas Chiller Leak Testing

Chiller Fault Finding & Diagnosis

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

Read more about chiller commissioning at Safework Method of Statement | Click Here


Open chiller controls panel showing PLC, relays, contactors and wiring

Chiller Controls

Chiller controls can be remotely operated and monitored, but in this article, we will be looking at chillers operating in local.

Each chiller has a panel where the lead or the lag chiller can be switched from. They have N+1 redundancy built in, so one of two chillers will normally be in standby with the other one running. The chillers in the photo are equipped with kilowatt hour meters because the customer wants to monitor their efficiency. He has targets to meet and wants to gauge the effect that our maintenance has in reducing his energy costs.

Condenser Pressure

The condenser pressure control is external and stand alone from the panel.

Transducer

A transducer is fitted to the discharge pipe near to the compressor. This gives a 0 to 5vdc control signal to the fan speed controller which is bolted to the frame. There is a minimum and a maximum value on the transducer, so the FSC is programmed to work out the pressure from the voltage.

Fan Speed Controller

415v on three phases are the input to the FSC. It uses solid state thyristors to regulate the output to the fans. This is according to the demand received by the transducer. Solid state means that all the parts are electronic with no moving parts. Fan speed controllers are really good at extending the life of the fans. This is because all of the fans operate together- smoothly and reliably.

Chiller Controls Digital Inputs

There are three essential digital inputs to the controls of any chiller. All of them have a volt signal out to them, which returns back to the panel. If there is a fault- the volts drop out.

LP Switch

This protects the chiller from a low pressure condition. Compressor and evaporator failure would result, so this device is set below the running pressure of the system, but high enough to offer protection.

HP Switch

If the head pressure control mentioned above were to fail, this device would save the chiller from damage from excessive pressure in the system. Components or the pressure relief valve can blow causing a catastrophic refrigerant leak.

Flow Switch

This device detects a lack of flow in the water system. Serious system failure would result if this part is not maintained properly. It needs to be periodically tested and adjusted at regular intervals.

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Chiller Controls Analogue Inputs

The essential analogue inputs on a chiller are the Water In and the Water Out sensors. These are usually NTC (negative temperature coefficient) that is to say: if you hold one in between your fingers and warm it up- the resistance will start to drop off. They usually read in kilo ohms which can be read on a standard multi meter. The program looks at these two sensors and using an algorithm, it calculates the loading requirement of the compressor. They can read incorrectly, so a sensor offset function is available in the software for adjustment. This is just one of the many checks and procedures that we carry out during our maintenance visit.

Chiller Controls Relays

In the photo you can see wires from the various devices around the chiller, wired into a row of relays. These, in turn, are wired into the white relay board at the top. This relay board has several expansion boards linked into it which are held together with an electrical ribbon. Next, the relay board is wired into the PLC... 

Chiller Controls PLC

The reason for these steps in between a device and the PLC is for protection. Sensitive electrical components can be blown due to an earth shortage. At each stage there is a volt drop from 240v to 24v and then to 5vdc.The programmable logic controller is the nerve centre of the chiller. This is where all the inputs go to and where all the digital outputs are sent from. The controller on this chiller is Beijer Electronics- it comes blank from the factory. User keys to operate the chiller are positioned below the display. It can be programmed to run most chillers and indeed it is often seen in factories running anything. A laptop plugs into it and the software for the chiller is uploaded. On one visit, we found a fault with this controller. We bubble wrapped it and took it to our electronics laboratory at Head Office. The issue was easy to resolve- it was just dust tracking across the back of the PCB and so corrupting the program.

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Chiller Controls Digital Outputs

The main digital outputs on this chiller are:

Compressor Run Signal

240v is sent to the compressor starter contactors. There are three: Star (lower amps for a soft start) then a timer switches over to Delta (higher amps for a more powerful running of the compressor) On the other end of the compressor windings is the Line contactor. This contactor runs with both the Star and the Delta contactors.

Float Valve

This is a camber where the level of refrigerant which is coming in from the condenser is detected. The level is transmitted to the PLC, where the program sends a signal to the expansion valve. It opens to the correct degree according to the load on the chiller.

Slide Valve

The compressor can run at 0% with the slide valve shut. When load is sensed from the Water In and Water Out sensors by the controller- the slide valve opens up. The position of the slide valve is detected by a potentiometer. This is calibrated from a minimum to a maximum position. The signal is 4-20 mA which the controller translates into the position of the slide valve.

MAXIMUS ADVANTAGE™

Whatever the problem with the controls, we can find a solution to resolve it. With years of industry experience and a fast supply chain, we offer a service that is second to none. Being able to retrofit is part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere.

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Air Cooled Chiller Condenser Maintenance

Shell & Tube Evaporator Maintenance

Screw Chiller Compressor Maintenance

Scroll Chiller Compressor Maintenance

Centrifugal Chiller Compressor Maintenance

Chiller Condensers

Reciprocating Chiller Compressor Maintenance

Chiller Controls Company

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

Read more about Chiller Control Basics on the Engineering Mindset | Click Here


Maximus Chillers sign outside our chiller maintenance company office

Chiller Maintenance Company

Diagnosis of Chillers

One of the most important parts of a chiller maintenance company is the diagnosis. If this is done wrong, the wrong parts are ordered and the return job goes wrong.

News Article No.7

For us at Maximus Chillers, it is imperative that we get the diagnosis right, so the return job goes easy. On a maintenance visit, a detailed Tick Sheet is completed with all the necessary readings and adjustments.

Chiller Maintenance Company Case Study

One of our engineers was on a maintenance visit recently and he found an electrical fault with a relay. An intermittent fault- so the most annoying to diagnose. The relay interlocks the compressor A1 run signal on the start contactor. The fault causing the relay to drop out was the high pressure condition. The high pressure switch was found to be in good working order with continuity back to the relay, so the relay was deemed to be not switching intermittently. The relay was changed with the available stock on site and the machine went back into seamless operation.

State of the Art Equipment

At Maximus Chillers we know that incorrect test equipment can lead to incorrect diagnosis. That’s why we have the highest quality equipment which is regularly inspected, replaced or calibrated. With a Fluke multimeter with fused leads- we diagnose the most complicated of problems. Sometimes a wiring diagram is not available, or the machine has been modified. Even wires disappearing into a conduit and ending up on the other end of the chiller can be traced and effectively diagnosed. You can rest assured that with the ongoing maintenance by Maximus Chillers- we will extend the useful life of any chiller.

Chiller Maintenance Company Technical Support Desk

For over the phone diagnosis, our contract customers enjoy the full benefit of our technical support desk. Faults are often something and nothing, or are just to do with how the machine was restarted. If we can get a chiller away over the phone, that saves us time and that saves you: the customer money too. Just part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere.

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Expansion Valves

We at Maximus Chillers have a comprehensive range of expansion valves, on the shelf, in our stores at Head Office in Droylsden, Manchester. There are three commonly used types of expansion valve used on a chiller:

Pulse Expansion Valve

This is a simple design of a solenoid coil lifting a solenoid valve and opening the diaphragm in the expansion valve. This allows the refrigerant to pass from the high side of the system into the low side. A sensor either side of the evaporator feeds back to the controls. The controls work out the length of time the valve stays open and the length of time the valve stays closed. Quite a simple idea and quite reliable from our experience too. The replacement of parts are a straight swap.

Electronic Expansion Valve

Another type of valve we stock is the electronic expansion valve. Similar to the above, this valve uses a sensor either side of the evaporator to work out the superheat. Another method of working out the superheat is a sensor and a transducer. Either way amounts to the same thing: the controls work out the difference in temperature and saturation point. The mechanical part of the valve is a step motor which winds all the way shut when the chiller starts. This is so that the controls can register step 0. As the valve opens, the controls record the amount of steps. It therefore knows the position of the valve to regulate a close control of superheat.

Thermostatic Expansion Valve

A thermostatic expansion valve is a completely mechanical and stand alone part. The pressure in the bulb increases with temperature and so forces the valve open. We have the full range of orifices for the commonly used varieties of valve on the shelf. Each orifice is used for a different application, ranging from low temperature -40°C saturation, through medium temperature 0°C saturation, to high temperature 20°C saturation. High temperature applications include laser chillers- the secondary refrigerant cools the oscillator and the laser head.

HFC Refrigerant

HFC refrigerant is being phased down to 21% by 2030. This is in accordance with F-gas guidelines and the emission reduction measures as defined in the Kyoto Protocol. This refrigerant, however, still remains to be the most popular type amongst chillers, with new chillers coming off the production line charged with, most commonly, R407c and sometimes R410a. R134a is also a popular chiller refrigerant most commonly used in flooded centrifugal chillers. The more the phasedown starts to pinch, the more the incentive to use a lower GWP (global warming potential) drop in refrigerant. This extends the useful life of the chiller, therefore removing the need to build a new chiller, with the associated high amount of carbon emissions.

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Evaporators

Eddy current Inspections by Chiller Maintenance Company

At periodic intervals according to the maintenance schedule, the end plates are taken off the evaporators and the tubes are inspected. We have calibrated eddy current instrumentation to assess the integrity of the evaporator tubing. This equipment uses electromagnetic coils to produce eddy currents, the electrical impedance is then measured. It picks up any cracks, pitting or corrosion. The conclusions are mapped onto a chart showing the tubes which are likely to fail. These tubes can be taken out of operation to prevent catastrophic system failure in the future. The system can then be pressure tested in accordance with F-gas leak testing requirements to prove the integrity of the system. Just part of the joined up, forward thinking of Maximus Chillers.

Chiller Maintenance Company Lagging

On our maintenance visits, one of a long list of checks is to check the insulation and vapour seal. If the lagging is not in place correctly, moisture from the air forms as condensation on the steel shell. This is not visible, so the condition of the steel can deteriorate dramatically over time. Where the lagging is in good condition, industry guidance states that it should not be removed to inspect. Where the lagging is in poor condition, however, it should be stripped back to the location of a good seal to inspect the integrity of the shell. For low temperature glycol or brine applications, rapid deterioration occurs as the shell is defrosting and re freezing between production cycles or defrost cycles. We heat treat the steel to remove all the moisture, then grind off any rust, before adding a two kinds of specialist paint available for sale at Maximus Chillers. We then match into the old lagging for a good join with our off the shelf varieties of lagging. The lower the temperature of the application, the greater the thickness of the lagging supplied.

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

For further reading on F-gas enforcement reforms visit RAC Magazine | Click Here


400 kw white chillers with panels open during air cooled chiller maintenance

Air Cooled Chiller Maintenance

A nice day to carry out air cooled chiller maintenance at a new site we have taken over in the South East.

News Article No.6

Our engineer attended site at around 9am with the risk assessment method statement having been sent in advance. A site survey was carried out to see if there were any additional risks. Should there have been any changes- the RAMS have a section for the additional risks and control measures. After gaining a permit to work, our engineer was issued with a security pass to access the chiller compound. Three chillers are located in the compound which feed air handlers for a critical application. Two of the chillers are multiple system, scroll compressor, air cooled chillers. The other is a single system screw chiller.

Program Settings During Air Cooled Chiller Maintenance

A complete download of the program settings is available in our engineer’s phone. This is to cross reference the settings, should one of them be accidentally changed by the maintenance engineers. On site engineers are the first port of call for chiller trip outs, with the responsibility to get the plant up and running. We offer real time assistance, over the phone from our Technical Support Desk and can send user manuals in PDF form, direct to their computer. The settings were found to be nominal, so a detailed analysis of the alarm history was carried out:

Alarm History During Air Cooled Chiller Maintenance

In reverse date order, the alarm history of all the systems was interrogated. There had been several system shut downs to carry out the periodic maintenance by the onsite personnel. The electricity having been shut down, there was a subsequent oil pre heating timer in the history too. On Chiller 2, System 1 however, there had been several low pressure trip outs. Our engineer decided to start the maintenance with this system by carrying out a full diagnosis of the low side of the refrigerant system:

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Superheat During Air Cooled Chiller Maintenance

The system runs on R410a refrigerant. This refrigerant has higher operating pressures in comparison with other HFC refrigerants. It has an efficient temperature range which can be seen on a pressure enthalpy chart. Below or above this range- the refrigerant loses efficiency and so has a lower coefficient of performance. The most common saturation point for this refrigerant is 0°C which corresponds to a 7 bar suction pressure in the evaporator. Above this is the superheat of the refrigerant returning to the compressor. On this occasion there was found to be 26°C of superheat and a suction pressure of 4 bar- close to the low pressure trip out. After careful diagnosis, our engineer decided to focus his attention on the expansion valve:

Thermostatic Expansion Valve

There are 4 forces acting on a TEV:

Liquid line pressure coming from the condenser.
Versus
Suction pressure down the equalising line from the far side of the evaporator. This compensates for the pressure drop across the evaporator and shows the true compressor side pressure.

Spring pressure acting upwards and closing the valve.
Versus
Bulb pressure forcing the valve open.

To reduce the superheat, the bulb should have forced the valve open. The refrigerant charge in the bulb acts upon the bellows to achieve this. The reason for the malfunction, on this occasion, was found to be the failure of the expansion valve orifice. It had become jammed- causing a shortage of refrigerant in the evaporator and high superheat.

Latent Heat

Our engineer was carrying out the above fault finding with one compressor running and the other two being held off. This was to prevent a low pressure trip. Where chillers are left running with a high superheat condition, the reduced amount of latent heat causes a higher cost in electricity relative to refrigeration effect (COP) The refrigerant carries on superheating without absorbing latent heat- pointless and inefficient for a chiller.

Chiller Pump Down

For convenience, this chiller can be pumped down and valved off using the service valves. The evaporator can be worked on after breaking in procedures are carried out. Therefore, we have arranged for this to be carried out before fitting the new expansion valve parts. These chillers also have the ability to pump down the refrigerant on receiving a fault feedback from the electronic leak detector. This is an added measure to lower the environmental impact of refrigerant leaks.

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Subcooling During Air Cooled Chiller Maintenance

This is cooling the refrigerant vapour down, through the latent heat phase and then subcooling the liquid down further. On System 2 of the same chiller, a subcooling issue was identified. 21 bar/ 36°C saturation was normal for that system as defined by the fan speed controller. Now, the system pressure was higher at 28 bar/ 47°C saturation, so our engineer decided to work out the subcooling. A very high reading of subcooling was recorded at 28°C this was diagnosed to be due to non condensables in the refrigerant:

System Non Condensables

Non condensables are gases that will not condense, such as, air and nitrogen. If nitrogen is not vented properly and a deep vacuum then achieved, the gasses will remain in the refrigerant system. When calculating the subcooling, the readings work out incorrectly due the presence of the gasses. This can lead to false diagnosis. The remedy for the issue was to arrange a full refrigerant decant, pressure testing and dehydration, before charging with new refrigerant.

Efficiency

Having good subcooling values on a refrigerant system is critical to efficiency. Where there is no subcooling- the refrigerant has not fully rejected all the latent heat from the condenser. This can be seen when looking at a PH chart and plotting the pressures and temperatures. This heat remains in the refrigerant and adds to the system along with heat added from the compressor and heat from the process. This is another reason the coefficient of performance is reduced and so incurring increasing electricity costs for the plant.

Economizer

These chillers are also fitted with refrigerant economizers- one for each system. They work by diverting some of the refrigerant from the condenser, through a small expansion valve, then through a plate heat exchanger. The rest of the liquid refrigerant passes on the other side of the plate heat exchanger and so is further subcooled.

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

For further reading on chilled water visit Wikipedia | Click Here


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

Chiller Service Company

Electrical Testing

A chiller service company can carry out electrical testing and diagnosis even when a wiring diagram is not available- our engineers can trace the wiring around a chiller.

News Article No.3

Doing this often aids with the diagnosis even when there is a wiring diagram, as having your eyes on a component often makes more sense than a symbol. In any case, our engineers carry out system testing with Fluke multimetes and ammeters.

F-gas Leak Testing by Chiller Service Company

We also carry a range of thermocouples and probes to be used in conjunction with our calibrated digital thermometers. We use these along with comparators to carry out leak testing. After fitting the probes, we first have a visual look around for a sign of a gas leak. All parts of the pipework and system components are inspected. Then, we carry out a full refrigerant diagnosis to determine that the refrigerant system is operating with a full charge. Reports for each chiller are completed and filed in the onsite F-gas leak register. A history can be built up to assess the serviceability of the plant and the frequency of any leaks.

Chiller Service Company Monitoring

Where intermittent faults are concerned, on site monitoring is required. If the job is not progressed on each visit, there is little point in a call out. We carry out tests during monitoring and ensure that the wiring is tight. Hopefully, waiting for the fault to occur whilst next to the machine. Alongside this, we rely on feedback from the end user, as regards, the symptoms and the circumstances of the chiller when the fault occurred. From this we extrapolate the diagnosis and decide the next step to take. This may be to attempt to move the fault to another machine or, at least eliminate one thing each visit.

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Chiller Service Company Evaporators

Shell and Tube

These have a rolled steel shell, welded down the seam with and end plate on either end. The water system pipes can be bolted to the sides or the end. The endplate can be removed for access to the waterside of the tubes. A strainer is fitted to the inlet to catch any foreign objects that may have been carried around the water system. Inlet and outlet gauges are fitted for the monitoring of the water system readings during a visit. 

Flooded

On larger chillers, the screw or centrifugal compressor is mounted directly on top of the flooded evaporator. The refrigerant is in its liquid phase on the outside of the tubes. These are arranged in a rack extending through the length of the shell. The warmer process water running through the tubes causes the refrigerant to boil off. A sight glass is usually available to check the state of the refrigerant evaporating on the copper tubes. The suction from the top of the evaporator goes round a baffle so as to prevent the slug back of liquid refrigerant into the compressor. The refrigerant flow into the evaporator is controlled by the expansion valve…

Expansion Valves

This takes the form of a fixed size orifice on the liquid line in between the shell and tube condenser and the flooded evaporator. The size of the orifice previously being calculated to match the mass flow rate of the refrigerant dictated by the compressor. Some newer systems have a variable orifice for the more efficient running of the plant. This is controlled electronically along with the loading of the compressor, relative to the available load.

Multiple System N+1

Smaller DX evaporators are usually multi system. This gives an N+1 redundancy of the plant. Indeed, when one side of a 2 system evaporator is having service work carried out, the other side continues to operate normally. Thinking ahead and allowing for additional capacity is essential when the application is critical, such as, a data centre or a hospital. When a redundant system comes online due to a failure- getting the failed system back up and running is a matter of urgency. For this we offer same day delivery of parts and a fully stocked mobile workshop.

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Chiller Service Company Condensers

Various configurations are employed to ensure good air flow through the condenser fins. The most popular being a ‘v’ condenser as the surface area is increased with this design. Powerful fans are used to reject the air and heat upwards and away from the chiller. Where system location causes the recirculation of air, duct work can be fitted to direct the air away from the chiller. The pressure is monitored using a HP gauge.

Pressure Transducers

Johnson Controls

A popular kind of pressure transducer that is used on condensers is Johnson Controls. These can be bolted onto the refrigerant discharge pipe to sense the system pressure. They have a 5vdc input that comes into the transducer on a red wire, a black wire is the ground and a white wire is the signal back to the fan speed controller. The transducer has a minimum to maximum range, so a chart can be used to determine if the signal is reading back correctly. On chillers where the transducer is wired directly in the controller- calibration can be carried out to offset the readings.

Keller

Another kind of pressure transducer is the 4-20mA type. It sends a mA signal back to the controller or the fan speed controller. 4mA is the minimum position, so this relates to the minimum of the transducer pressure range.

R134a Refrigerant

R134a refrigerant operates at a lower pressure in a condenser than the other commonly used HFC refrigerants. If you were looking for a chilled water set point of 6°C in the UK ambient for example, the R134a refrigerant saturation on the high side of the system would be around 36°C Latent heat from the water system and heat added into the refrigerant from the compressor are rejected from the condenser. As the refrigerant passes down the condenser tubes, cool air blowing across the outside of the tubes, cools the refrigerant vapour down through the latent heat phase and into a subcooled liquid.

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Chiller Service Company Compressors

Centrifugal Compressors

This kind of compressor has a lower volumetric efficiency compared with the positive displacement compressors below. This is because the refrigerant is compressed using centrifugal force off the tip of the impeller, instead of being mechanically compressed. The advantage of this kind of compressor is a high mass flow rate of refrigerant. These compressors are used in factories where a large amount of chilled water is required to cool the process. They are also used in countries where district cooling is used. The chillers are arranged in rows in a chiller hall and are piped into the district cooling loop.

Screw Compressors

Oil used to lubricate the bearings is also used to create a seal between the rotors. Computer aided design (CAD) software and computer numerical control (CNC) grinding machines are used in the construction of screw rotors. The shape of the rotors is designed to compress the refrigerant along the screw. The length of the screw that is available to compress the refrigerant can be adjusted with a slide valve. Any stage of loading between 0- 100% can be achieved. This is regulated with a slide valve potentiometer. Screw compressors are very reliable and have a long service life. They also have a low vibration reading which ensures a lower instance of refrigerant leaks around the compressor.

Scroll Compressors

A service free compressor. Service free assuming that the rest of the system is functioning correctly. This kind of compressor relies on oil migration around the system. The oil is entrained along the inside of the pipework, around the system and back to the compressor. An oil level sight glass is fitted into the body of the compressor at the required level. Refrigerant shortage can cause the oil to stay in the bottom of the evaporator, causing a low oil level condition in the compressor. We can be scheduled to attend site to drain the oil, then pump new oil into the compressor.

Compressor Failure

When any of the above compressors fail, you are in safe hands with Maximus Chillers. We have the capability to lift and shift the compressor to our remanufacturing facility for a full overhaul. The reason for the failure is diagnosed to ensure the new compressor does not fail for the same reason. Improving the reliability of your plant and extending its life is what we are all about- if we can reduce your service costs- that makes us happy! All temperatures and pressures are recorded to ensure the replacement compressor goes into seamless operation.

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

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

Read more about pressure sensors on Wikipedia | Click Here


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

Read more about the centrifugal vapour compressor at the Institute of Refrigeration | Click Here


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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Chiller Service Company Visit

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Read more about reducing refrigerant leaks at the Institute of Refrigeration | Click Here


Controls panel open during chilling plant maintenance

Chilling Plant Controls Maintenance

Prior to this chilling plant controls maintenance visit, another contractor had changed some of the settings and adjustments in the controllers. They did this while they were diagnosing a fault with the water system and the pumps. Therefore, this visit was to recommission the plant and to resolve the issues resulting from the adjustments.

Chilling Plant Flow Controls Maintenance

The flow controls were found to be set wrong. Therefore, our engineer adjusted the pumps, then various valves on the water system, a little at a time, while monitoring the controller. Full load and part load readings were taken until they came to within standard industry limits.

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Compressor Run On Time

A timer had been adjusted which made the compressor wait to stop after reaching 0%. In the meantime, some more heat would build up in the water system and the compressor slide valve would open up a little. The result was that the compressor would run for an hour with the slide valve shut most of the time. The oil pump carried on pumping during this time resulting in a head of oil building up in the discharge pipe- all the way back up to the oil separator. Then, a low oil level fault had occurred. This being confirmed by the sight glass on the oil separator. The compressor had enough oil charged into it to allow a start up. During the start up, a low oil level timer counts down. As soon as the compressor loaded and started pumping, the oil level returned to the correct level on the sight glasses. The timer was adjusted along with the dead band to ensure the chiller off cycled after achieving set point.

Slide Valve Potentiometer

The slide valve potentiometer has a configuration mode button. It can be pressed to set the 4mA or 0% position. This is the usual position of the slide valve as a spring and 2 drain valves return it to the start position. The slide valve can then be manually opened in the program. Then, the potentiometer button can be pressed to set the 20mA or 100% position. “Chattering” can occur on the fully closed position so a setting is available to only close the slide valve to 2%.

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

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Follow this link to read more about potentiometers on Wikipedia Click Here


Two dark green centrifugal chillers undergoing maintenance in plant room

Centrifugal Chiller Maintenance

At the beginning of the year we completed centrifugal chiller maintenance for one of our customers in America. A last overseas trip for the moment given the current world lockdown. The machines in the photo chill water that is pumped around a university campus.

Centrifugal Chiller Maintenance of Redundant System

The plant has a water cooling shell and tube evaporator and a water cooled shell and tube condenser. It has been designed according to the N+1 principle: N being the amount of cooling required and 1 being that same amount of cooling again. Each chiller has enough capacity to satisfy demand. Given the large size of the campus, this principle was critical to keeping the University functioning should system failure occur. The chiller on the right was the lead chiller on arrival. After taking detailed readings during the maintenance, our engineer switched that chiller over into being the lag chiller and took readings from the chiller on the left. He rotates the lead/ lag of the chillers on each visit to balance the run hours of the compressors.

Volumetric Efficiency

Centrifugal chillers have a lower volumetric efficiency compared with positive displacement compressors such as screws and recips. This is because the impeller does not mechanically compress the refrigerant like a piston in a reciprocating compressor. This kind of compressor relies on centrifugal force to spin the refrigerant off the tip of the impeller and onto the next stage. The refrigerant is then discharged from the compressor.

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Mass Flow Rate

The above is more than compensated for with a high mass flow rate. That is to say: a high volume of refrigerant circulates around the system at its operating density. A large capacity machine is cost effective when considering energy efficiency and centrifugal chiller maintenance costs.

Gantry Crane for Centrifugal Chiller Maintenance

The gantry crane in the picture is available to aid with the lift and shift of the compressor, should compressor failure occur. Maximus Chillers are specialists in the overhaul of centrifugal compressors. We can arrange the lift out, transportation, strip down and reassembly of your compressors. All of our strip downs come with a 12 month warranty to give you peace of mind and confidence in our ability.

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Follow this link to read about centrifugal compressors at The Engineering Mindset | Click Here


Green chiller panel with doors open, showing contactors and PCBs during water chiller maintenance

Water Chiller Maintenance

Maximus chillers provides water chiller maintenance to all kinds of machines. Some of which have kilowatt hour meters fitted. This means we can monitor the reduction in energy consumption, directly as a result of our maintenance being carried out.

Efficient Water Chiller Maintenance

Maintenance is carried out to ensure every aspect of your chiller is running efficiently. We believe our maintenance checklist is the best in the industry. It looks in detail at the running conditions of the plant, component adjustments and the parameters in the controls. The checklist is used to assess if there are problems that are starting to occur before a safety shutdown happens. Below are some of the issues that we keep on top of to increase the efficiency of your plant.

Shell and Tube Insulation

The build up of dirt acts as an insulator in shell and tube heat exchangers. These are used for the evaporation and the condensing of the refrigerant.

The Evaporator

In the evaporator, should the tubes be fouled, there will be a reduction in latent heat absorbed into the system. This will cause the plant to stay on longer and use considerably more energy. Should the tubes become considerably fouled, the chiller will malfunction and eventually system shutdown will occur.

The Condenser

In a shell and tube condenser, the reverse of the above will occur. Tube fouling, acting as an insulator, will prohibit the rejection of heat from the system. The head pressure control will open the condenser controls to try and assist in heat rejection. Heavy fouling will cause an increase in the consumption of energy. Eventually a safety shutdown will occur causing loss of production.

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Compressor Loading during Water Chiller Maintenance

If the loading of the reciprocating compressors is faulty, the plant will not be able to effectively match the load.

Over Loading

Too much loading may occur, causing the water chillers to achieve set point too quickly. The plant will then go through the off cycle. This means that the plant will have to load back up, using more energy than matching the load continuously.

Under Loading

Should the plant be unable to load up to the required level to match the load, this will cause the water temperature to creep up and the lag chillers being called for to match the load. More chillers running than necessary dramatically increases energy consumption.

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Visit the Refcom site to read about leak checking during water chiller maintenance | Click Here


Industrial refrigeration oil change showing ammonia warning sign

Industrial Refrigeration Oil

An industrial refrigeration oil visit was arranged because of a return issue. Several fans had been down on the air cooled system. This causes the system to unload so as to prevent a fault occurring. The lower mass flow rate of the refrigerant caused oil to migrate to the low side of the system. Several vessels are available with various forms oil return. These vessels and the oil cooler were valved off. A two man team with the correct ammonia PPE and breathing apparatus carried out the job.

Industrial Refrigeration Oil Recovery

Only some of the oil was recovered from the plant. Therefore, the engineers decided to add new oil to get the system running. The only problem with doing this is that once running the machine, the oil has to be got back out. Therefore, the oil had to be adjusted a second time to resolve the oil return issue.

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Fan Decks

For this visit, scaffolding had been erected in accordance with the Risk Assessment. The old fan decks were lifted out by the two man team. A really good team was sent out: one of the men was more technical and the other more mechanical- complementing each other with their different skill sets. The new fans were an updated version and the wiring was different. The fault link had to be adapted, but the 0-10v input from the controller was the same. The controller reads the pressure from a transducer, then sends out a voltage which the fan turns into the corresponding speed.

System Testing

The fault link had been correctly modified, so the testing of the system was carried out. The machine loaded up to 62% and monitoring continued during the rest of the visit.

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

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Read More about International Institute of Ammonia Refrigeration Technology and Standards.

 


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