Chiller Commissioning

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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Blue ammonia chiller with panel open during chiller controls company visit

Chiller Controls Company

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

Non Condensables

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

High Subcooling

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

Air Purging

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

Subcooling Readings

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

Dalton’s Law of Partial Pressures

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

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Electrical Problems

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

No Heater Burn Out

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

Ohms Checked by Chiller Controls Company

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

Run Signal

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

Blown Relay

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

Monitoring by Chiller Controls Company

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

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Software Upgrade by Chiller Controls Company 

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

Chiller Controls Company Reliability

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

Chiller Controls Company's Test Rig

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

Laptop Plug In

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

Chiller Controls Company Testing and Adjustment

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

Completion

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

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Chiller fault finding & diagnosis tool case and car boot

Chiller Fault Finding & Diagnosis

Accurate chiller fault finding & diagnosis saves money! This is because when the wrong parts are ordered and your machine still does not work- it has been a wasted visit with unneeded parts.

News Article No.12

Expert Training for Chiller Fault Finding & Diagnosis

All of our engineers are time served, attending the Government approved college course. This includes the F-gas HFC and BESA ammonia refrigerant handling certificates. Our engineers also go through rigorous training at The Maximus School of Chillers at Head Office in Droylsden. Here we have various chiller types ranging from small air cooled chillers, to the panels for large water cooled, screw and centrifugal chillers. They have been wired up as test rigs to simulate the various fault conditions. The manager will simulate a fault and the engineer will then have to follow it through to a successful diagnosis. This off site training ensures that when our engineer attends site, he is armed with all the skills he needs to follow through the fault finding easily.

Technical Support Desk

Whilst on site, our engineer is connected to our live stream, real time Technical Support Desk on his laptop and smart phone. He can also face time the support desk on his device. We often find that it is a lot easier to show somebody something than describe it. This service is available to you the customer too- free of charge. It is just one of the many features that help us to achieve The MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. PDF chiller manuals and wiring diagrams can be sent to our engineer’s phone and then printed off on your computer. This means that you have all the technical information you need, in the chiller panel for when our engineer is not in attendance. Just face time our support desk and we will talk you through. This helps to keep your service costs down as it will often save you the cost of a call out.

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Mobile Workshop for Chiller Fault Finding & Diagnosis

Each car boot is a mobile workshop with a blueprint of equipment repeated across each car in our fleet. We have recently opened The Spanish Office with one engineer down there now too. Our fleet of cars in the UK are Peugeot 508 and in Spain our engineer has a Seat Arona. In both countries the equipment is duplicated and standardised. This is so that Head Office knows what each engineer has at his disposal while on site, so he can find out what the problem is- fast!

Fuse Wire

It is the small things that we carry that help- fuse wire for example. This is so that a big box of spare fuses does not have to be carried.

Contactors

We carry 4 medium sized contactors which have 24vac, 24vdc, 110v and 230v coils. Each has NO (normally open) and NC (normally closed) contacts. This means that a blown relay, or a process chiller compressor single phasing- will be repaired while on site. Just another cost saving exercise for you the customer.

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Fluke Multi Meters

Our multi meters are calibrated annually for accuracy. They are equipped with fused leads to protect the engineer when working on high voltages. They have long, thin prongs too for access to the most difficult locations. Electrical plugs which are fixed onto relay boards are a good example. We test:

Resistance Temperature Detectors

RTDs are sensors that are often: NTC (negative temperature coefficient) where the resistance drops when warmed. PTC (positive temperature coefficient) where the resistance goes up when warmed. The sensor reacts to temperature in a predictable way, so a chart can be composed by the manufacturer. This chart shows the resistance reading, which should correspond to a given temperature. When a resistance reading on the multi meter is not where it should be on the chart- the sensor has failed. We carry crocodile clips for our multi meter prongs because sensor wires can be difficult to hold against our standard prongs.

DC Chiller Fault Finding & Diagnosis

We mostly fault find the direct current which is associated with the controls of a chiller. DC is also found in inverter drives before it is re inverted back into AC on the compressor. We usually fault find inverter drives on either end, however, when the volts are AC. PCB electronics usually run on 5vdc as computer components work well with this kind of voltage. That is not to say that there is not 24v and 230v present on a PCB, it may be part of other things that the PCB is doing. We have the function to read DC on our multi meters.

AC Chiller Fault Finding & Diagnosis

The most often used function on our multi meters is AC. This is because most components around a chiller panel are usually AC. The safety chain including the low pressure, high pressure and flow switches are usually fed by a 230v supply. The 415v line volts to fans, pumps compressors etc. are AC too. On large air cooled chillers, the panel is quite big to control all of the components and devices around the chiller. On large screw and centrifugal chillers, it is just a small panel with the compressor starter panel usually being separate.

Fridge System

Our calibrated gauges can be fitted to a HFC or ammonia chiller with a selection of fittings for each machine type. We carry digital thermometers with various probe types to access the different parts of the machine. Usually, however, the pressures and temperatures are available on the chiller controller. We use these pressures and temperatures, along with a comparator app to diagnose the condition of the fridge system. Superheat and subcooling values are worked out which are transmitted, real time, to our technical support desk. This means, along with the data plate of the chiller which is stored in our system, we can provide you with a Quote for the service job while the engineer is still on site.

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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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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


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

Control Panels

The first thing our engineers check at the start of the maintenance is the control panel of the chiller. 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

RCDs 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°C 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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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 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 or 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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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.

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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


6 large air cooled chiller condensers maintained with 12 fans each

Air Cooled Chiller Condenser Maintenance

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

Fan Speed Controllers

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

Air Cooled Chiller Condenser Maintenance Cleaning

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

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Design Considerations for Air Cooled Chiller Condenser Maintenance

The kind of condenser in this article is:

Multiple Row Tubing

3 Rows

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

6 Rows

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

Finned

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

Forced Convection Type

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

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Fan Replacement during Air Cooled Chiller Condenser Maintenance

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

Pressure Relief Valves

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

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

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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 often made 'in house' so they can be 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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