Chiller Call Out

Ammonia warning sign and yellow light flashing during chiller call out

Chiller Call Out

Chiller call out is the essence of what a company like Maximus Chillers is all about. It is a time when our engineers come into their own. Read on to see examples of how we do it…

News Article No.22

Chiller Call Out for Ammonia Leak Alarm

At first sight this appears to be a dangerous situation as ammonia is very harmful to human health. This is because of its corrosive and toxic characteristics. Each of our engineers carries breathing apparatus and full length ammonia PPE should it be required.

Location Assessment

The work location in the photo is assessed using an NH3 detector. This is sensitive enough to detect lower than the 35 parts per million short term exposure limit. The detector is fitted to the work wear of our engineers whilst near to the plant. When the alarm does not sound and there is no smell of ammonia- it is safe to proceed.

Electrical Fault

Usually this alarm is due to a controls issue rather than a leak. There are various reasons:

UPS and Alarm System Malfunctions

Chiller panels for this kind of plant have a UPS (uninterruptible power supply) This is a battery which is charged by the mains. When a power failure occurs, the charge in the battery supplies 240v to the ammonia alarm. This means that the chiller continues to be protected. When malfunctions occur to the UPS or the alarm system, the yellow warning light and siren is activated which needs to be manually reset.

Sensor Failure

The sensors have to be calibrated at regular intervals. The base setting of 0 parts per million has to be set and then the trip outs of 35 and 25 parts per million. These sensors can be knocked out of calibration by small leaks over a long period of time, or they can malfunction internally. If you require the service of your leak alarm- email our Technical Support Desk and will arrange a site visit.

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Chiller Call Out for BMS Failure

Chillers can get blamed for everything as the customer can notice a building that is getting warm and then call us out. An example of this is when a new customer of ours signed up to a maintenance contract after a long period of neglect. They did so because the office workers in a large office block had started to leave their desks and walk out of the building.

Investigation

When our engineer attended site, he found various faults with a row of four, 500 kW chillers on the roof. There was found to be N+1 redundancy built in, so he considered there to be sufficient cooling available to satisfy demand.

No Run Signal

Despite there being available load, the chillers were not being given the run signal from the BMS. The toggle switches on the BMS panel did not give the run signal to the chillers when they were put into Hand. This was found to be because of other issues with the poorly maintained panel.

Link Out

Our engineer therefore decided to link out each of the chillers in their respective panels. He consulted the wiring diagram and made the modifications accordingly. He then entered the password for that particular chiller and adjusted the program settings. These changes made the chillers stand alone and not reliant on the BMS run signal.

Chiller Call Out for Pump Sets

The pump sets were also found to be in poor condition. There were found to be failed pumps, blown contactors and defunct controls. The good news was that by changing components in the panel, he managed to at least one of each pair of pumps going for the various water systems used for around the building.

Pressurisation Unit

This is a machine with an internal pump and a pressure switch which is used to maintain the pressure of the water system. Both the run and the standby pumps were found to have failed with other component failure in the unit as well. Our engineer decided to manually fill the water system with mains water to build up the pressure.

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Get it Away

Having done all this, our engineer got the chillers away and watched the water temperature come down from 24°C to 6°C. As the chiller systems came down to set point, they unloaded to match the demand from the building.

Return to Work

The office staff started to return into the building and resumed work at their desks.

Fault Finding

Now that the pressure was off, our engineer carried out the necessary fault finding to the systems that had failed:

Chiller Call Out for Refrigerant Leaks

Three of the systems were found to be locked out with low pressure alarms. He assessed the quantity of recovery cylinders and refrigerant that was required. Then, he submitted a report to Head Office for a return visit to carry out the repairs.

Blocked Condensers

Some of the systems were found to have blocked condensers. The call out was during the summer when a high pressure condition was more likely to occur. A build up of contaminants had reduced air flow and caused the high pressure switches to be activated. We arranged a site visit with a special cleaning agent to remove the contaminants and restore the air flow through the condenser fins.

Chiller Call Out for Flow Switches

These are a switch used to detect water flow and two of them were found to have had failed. There are various types for different applications. We select a suitable flow switch and then make the necessary adjustments to the internal control screws. This ensures that the switch will function correctly when problems with the water system occur. 

Related Articles:
F-gas Chiller Leak Testing

Chiller Fault Finding & Diagnosis

Air Cooled Chiller Condenser Testing

Chiller Breakdown

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 gas detectors on Wikipedia.


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

Improve Chiller Efficiency

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

News Article No.18

Improve Chiller Efficiency with a Clean Condenser

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

Improve Chiller Efficiency by Removing Evaporator Thermal Insulation 

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

Blocked Strainer

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

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Improve Chiller Efficiency with Correct Refrigerant Charge

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

Refrigerant Leak Repairs

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

F-gas Register

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

Blocked Pump Fan

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

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Waste of Money

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

Maintenance Visits Improve Chiller Efficiency

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

Mobile Workshop

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

Kilowatt Hour Meters

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

Scheduled Chiller Maintenance

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

Technical Support Desk

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

Related Articles:
Air Cooled Chiller Condenser Testing

Shell & Tube Chiller Evaporator Maintenance

F-gas Chiller Leak Testing

Planned Preventative Chiller Maintenance

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

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


Nitrogen cylinder and regulator with gauges attached for f-gas chiller leak testing

F-gas Chiller Leak Testing

Regulations

The regulations for F-gas chiller leak testing have been devised to reduce the environmental impact of HFC refrigerants. They are standardised regulations which are implemented across Europe. Now that we have left the EU, we will continue to be aligned with these regulations.

News Article No.14

Leak Test Frequency Required

The frequency of leak tests depends on the type and quantity of the refrigerant. For example, a system which runs on R134a, the frequency is:
• once every 12 months for a charge less than 3.5 kg.
• once every 6 months for a charge less than 35 kg.
• once every 3 months for a charge less than 350 kg.
All of our maintenance schedules far exceed these minimum requirements. This is because our customers require maintenance visits more often to ensure the efficient running of their plant.

Static Leak Detectors

These leak detectors must be fitted to systems with more than 500 tonnes of CO2 equivalent. For the refrigerants most commonly used in chillers this is:
• R410a 239 kg
• R407c 282 kg
• R134a 350 kg

Global Warming Potential

The GWP numbers below represent the amount of greenhouse effect each refrigerant has, by comparison with an equal mass of carbon dioxide:
• R410a 2,088
• R407c 1,732
• R134a 1,300

Now we have had a look at some of the regulations, let’s have a look at a day in the life of our engineers here at Maximus Chillers. Read below for three different examples of leak testing carried out in the field…

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Pressure Testing Following a Leak

In the photo a leak has just been brazed on the condenser. It is recommended in the industry to use a steel braided line with a ¼ turn valve. This is so that if a nitrogen regulator malfunctions, it can be valved off, instead of a system being filled with bottle pressure from the cylinder. For a small system, this could cause a catastrophic explosion. We decided, therefore, to use a small cylinder which would expand into the large volume of the chiller. Should this fault occur, the safe working pressure would not be exceeded. This was taken into account when writing our Risk Assessment Method Statement. The pressure was built up in stages until the test pressure was achieved. This was recorded on our Pressure Test Certificate and witnessed by the customer. The result of the pressure test 4 hrs later was satisfactory and also witnessed by the customer.

Follow up Actions

A return visit was arranged 2 weeks later to leak test the chiller again. Our engineer carried out a visual inspection of all of the parts of the refrigerant pipework. He then used an electronic leak detector to see if it went into alarm. All was okay, so he completed the F-gas Certificate and left it in the customer’s file.

Routine F-gas Chiller Leak Testing during Maintenance

On another site, we look after 6 air cooled MW chillers in a row outside a building at a petrochemical facility. Our engineer ran the systems up, one at a time, to 100% so as to show up any refrigerant shortages. He was looking at the subcooling and superheat values. Two of the systems had poor readings which alerted his attention to a potential leak. On one of the systems, the poor readings were found to be caused by a faulty expansion valve. On the other, he diagnosed that the chiller was running short of refrigerant. He then carried out an inspection and found signs of a leak on a liquid pipe, just after the filter/ drier. The system was locked off with the refrigerant valves closed either side of the leak. This was to prevent the refrigerant from carrying on leaking to atmosphere. Then, he sent a report into Head Office detailing the estimated refrigerant addition needed to replace the refrigerant lost. Refrigerant removal was not needed as the area of the leak had been valved off from the rest of the system. He also detailed the materials required for the job and the necessary labour time that would be needed.

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Looking for a Leak

There are a variety of methods that can be used to identify the location of a refrigerant leak. Here are some examples…

Ultrasonic F-gas Chiller Leak Testing

An ultrasonic leak detector uses a microphone on the end of a wand. This is connected to a battery and processing pack, which is where headphones are plugged into. The sensitivity can be adjusted on the processing pack until a good working level is found. The various components on the chiller can then be inspected to find an audible sound of a leak.

Electronic F-gas Chiller Leak Testing

Otherwise known as a sniff tester, the electronic leak detector is one of the most popular types of leak detectors. The battery can be recharged via the cigar lighter in a car, or can be recharged back at the office with a transformer plugged into the mains. The heated diode sensor and the filter can fail or need to be replaced, so replacement parts are available. The instrument needs to be calibrated to a no refrigerant atmosphere, then it takes samples of the atmosphere being tested. It compares the two atmospheres and looks for a difference. Most electronic leak detectors work with all HFC refrigerants.

Bubble Up F-gas Chiller Leak Testing

There are a variety of bubble up leak detection sprays that are available off the shelf. At Maximus Chillers we make our own leak detection solution in our laboratory at Head Office. We mix two chemicals together in the correct proportions. This solution is carried in sprayer bottles in the boot of each of our company vehicles. When looking for a leak, our engineers use it around the suspected areas of a leak. It is the best form of leak detection that we know, as it can find the smallest of leaks, right up to large leaks which are audible to the ear.

Related Articles:
Chilling Plant Service

Chilled Water System EEV Service

Water System Service of Evaporator

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Breakdown

Chiller Fault Finding & Diagnosis

Chiller Commissioning

Air Cooled Chiller Condenser Testing

To read more about the f-gas chiller leak testing procedure hit the Tag at the top of the page.

Read more about checking F-gas equipment for leaks on the Government website


Blue recovery unit with a grey recovery cylinder during a chiller breakdown

Chiller Breakdown

A rainy day for a chiller breakdown for our engineer in the North West.

News Article No.8

Electrical Faults during Chiller Breakdown

Our customer called us out because he was having electrical faults with the chiller. The power supply to part of the panel had gone down and he required our assistance. Our engineer found a blown fuse which he replaced and tested operation- it blew again. Using his multimeter, he followed the diagnosis though to an earth fault on the flow switch…

Water System Flow Switches

The flow switch vapour seal had failed allowing rain water to ingress. This caused an earth failure on the 240v control circuit, and so blowing the fuse. The customer raised an order forthwith and so our engineer replaced the flow switch with the stock from his car. Each of our engineers keeps a range of flow switches for a variety of applications…

Stainless Steel

Where water system chemicals are corrosive, we carry corrosion resistant flow switches. This type has a longer working life due to the use of stainless steel. They are more expensive due to the higher manufacturing costs, but they are worth the money as they are less likely to fail, causing a potential loss of production.

Outside Use

This was the type fitted by our engineer on site in this news article. It has been developed and tested across a range of adverse weather conditions including freezing conditions and heavy rain. The electrical and switching compartment is protected by a sealing gland to keep the weather out. A rubber ‘o’ ring provides the seal into this compartment.

Inside Use

Some applications have the flow switch located inside the building in the plant room with the control cable extending out to the chiller controls. Another configuration allows for the flow switch to trip out the building controls and so dropping out the run signal to the chiller. In either case there is no need for weather proofing. This kind of flow switch is cheaper due to the lower construction costs.

High Pressure

Some water systems operate at considerable pressure. Therefore, high pressure flow switches have been developed for this application. They are capable of preventing water ingressing from the water system and into the electrical and switching compartment.

Test and Adjustment

Our engineer carried out testing and adjustments to the flow switch to ensure that it ran reliably. He achieved this by monitoring the water system readings and measurements against the design specifications of the switch. When he got it to settle down, he replaced the fuse and ran tested the chiller...

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Condenser Fans

The condenser fans were not coming on at all at first and later only slowly. They are controlled by a fan speed controller which is sensitive to pressure. A minimum value of volts is supplied to the fans, so as to prevent stalling and over heating of the internal motor windings. The fans were found to be in good working order, so he decided to turn his attention to…

Pressure Temperature Relationship of Refrigerant

There was found to be a lower pressure and so a lower temperature in the condenser. After careful fault finding and diagnosis involving putting the pressures and temperatures into a calculator, our engineer decided that the chiller was running short of refrigerant. This is consistent with Charles’s Law of Constant Volume. It is one of the fundamental scientific principals of how a chiller works: the higher the pressure- the higher the temperature/ the lower the pressure- the lower the temperature.

Recovery Units for Refrigerant

After receiving a further order from our customer, we gave the go ahead to our engineer to use his recovery unit to decant the gas. The refrigerant is sucked into the unit using a small one cylinder reciprocating compressor. The compressor discharges into the on board condenser which is cooled by a fan. The subcooled refrigerant travels down a refrigerant hose which is connected to the recovery cylinder in the picture. After this process was complete, he started looking for a leak...

Leak Testing and Pressure Testing

The leak was identified on the flange for the expansion valve. This component was removed, cleaned with our in house refrigerant grade solvent, then the joint re made with a compound suitable for the temperature range of the component. After a satisfactory nitrogen pressure test, the evacuation process can begin…

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Refrigerant System Vac Pumps

Each of our engineers carry a high capacity vacuum pump of the highest quality. We believe in investing in state of the art equipment as this is part of how we provide the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. Good equipment makes the job go easy.

Vane Pump

The pump works by sucking vapour into the inlet port. A rotary vane system extracts the vapour and discharges it through the top of the pump module. Oil is used to lubricate the vanes that slide around the pump cylinder. The vanes are kept a tight fit against the cylinder with the use of springs. As our pumps are high capacity, an oil filter is fitted to the outlet with a gauze inside to catch any oil droplets.

Electric Motor

This motor fits onto the back of the vane pump module. It comes from the factory set to 240v, but we change the pins for the electrical connections to convert it for use with 110v. This is because customers and engineers demand the use of 110v as if is safer for use in the UK climate. The 110v plugs and extension cable are shrouded and weather resistant. Weather resistant does not mean weatherproof, so we take measures to limit the exposure to adverse weather conditions. The pump motor, however, is not weather resistant at all, so care is taken to locate it somewhere dry. After a long time running, the motor runs hot, so our engineers take readings and carry out adjustments to ensure that it stays within its nominal operating temperature range.

Oil Changes during Chiller Breakdown

The vac pump oil is changed before each use with our specialist grade, high quality oil. Contact our office for prices and delivery times. The manufacturer of the pump recommends these oil changes as moisture and impurities absorb into the oil and so reduce its performance, also the working like of the pump.

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Refrigerant System Evacuation

Having set up the vacuum pump, our engineer started the evacuation process.

Torr Gauges used During Chiller Breakdown

We use analogue Torr gauges as they are more reliable than digital ones. Also, they do not need batteries and it does not matter if they get wet. Our engineer attached the Torr gauge to a suitable part of the system with a refrigerant hose, ensuring that a good seal was made between the components with a sealing compound.

Fittings used during Chiller Breakdown

Fittings were used to get between the different thread types from the vac pump to the fridge system. Having warmed up the pump for half an hour he was ready to start the process.

Non Condensables Removed during Chiller Breakdown

One purpose of evacuation is to remove the gasses that will not condense such as nitrogen remaining in the system from pressure testing. Another non condensable is air that has entered the system from when the expansion valve was removed. These non condensables affect how a fridge system works according to Dalton’s Law of Partial Pressures: that all gasses in a vessel act as if they are on their own. The non condensables cause a higher head pressure in the condenser. When this pressure is added into our calculation- it throws out the sum and so gives a false reading of subcooling.

Dehydration during Chiller Breakdown

The other purpose of evacuation is to dehydrate the system. Water, as we know, has a boiling point of 100°C at sea level, which is 1bar absolute or 760 Torr. As you start to drop the pressure, so correspondingly, the boiling point also drops. For example, water boils at the top of Mount Everest at around 68°C. If we continue vacuuming a refrigerant system, eventually we can remove all moisture by dropping the pressure below the saturation point of water. This works even in the winter in UK ambient conditions. Moisture in the system causes system failures and malfunctions leading to expensive breakdowns.

Related Articles:
Chilling Plant Service

Chilled Water System EEV Service

Water System Service of Evaporator

HFC Chiller Service

Process Chiller Vacuum Service

Chiller Service Company

Industrial Chiller Service

Chiller Service Company Visit

Chiller Fault Finding & Diagnosis

F-gas Chiller Leak Testing

Chiller Commissioning

Air Cooled Chiller Condenser Testing

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

Read more about rotary vane pumps at Wikipedia


Large air cooled brown chiller with test equipment during planned preventative chiller maintenance

Planned Preventative Chiller Maintenance

Featuring planned preventative chiller maintenance, which is part of a series of longer, in depth articles.

News Article No.2

This time concentrating on the checks, adjustments and diagnosis our engineer carries out while on site. We can extend the life of your plant and reduce energy costs- just with the effect of our maintenance. As well as completing a detailed checklist, which is sent to your office in PDF form, our engineer carries out extensive F-gas leak testing.

Planned Preventative Maintenance of Chiller Controls

The first part of the maintenance is carried out to the controls of the redundant systems. This is because all the pressures and temperatures should be reading the same. If not, this is an opportunity for:

Sensor Calibration

Before calibrating a sensor that is reading out, our engineer carries out a diagnosis to assess the serviceability of the sensor. With NTP (negative temperature coefficient) and PTC (positive temperature coefficient) sensors, the resistance is taken at a given temperature, which is then compared with a chart. With pressure transducers the 0-5vdc feedback signal is analysed to see if it is within the allowable tolerance. Once this diagnosis is complete and the sensor is deemed to be in good working order, our engineer will then calibrate the sensor. A password is entered into the PLC (programmable logic controller) to gain access to the service menu. From here, he can select the particular sensor, then offset it by the required amount. A lot of controls are not linear, that is to say, a sensor reading 2°C high being reduced by 2°C may not calibrate correctly. An amount of trial and error is often required. Also, monitoring the sensor against a digital thermometer at various temperatures is carried out.

Program Settings and Timers

Each program setting and timer in the various menu levels is checked against the previous maintenance checklist. Sometimes these are changed accidentally by the onsite engineer when looking for something else- it is easily done.

Planned Preventative Chiller Maintenance of Safety Chain

Each component on the safety chain is manually tripped or the fault condition is replicated to cause the device to trip. This part of the PPM (planned preventative maintenance) is essential to ensure the safety chain protects the chiller during a fault condition. Compressor failure or evaporator freeze up can occur with dramatic cost implications. We routinely prevent small problems, such as a faulty switch, becoming big problems.

Planned Preventative Chiller Maintenance of Wiring

Each wire on the chiller is checked for tightness including the fans (on air cooled chillers) This includes the compressor motor connectors and compressor contactor contacts. Loose line wiring will cause breaker and fuse faults. Loose control wiring will cause error messages and chiller faults. This is a call out in between visits that can be eliminated. With the effect of our maintenance, any chiller becomes more reliable and has lower energy costs.

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

Superheat

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

Refrigerant Shortage

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

Expansion Valve Failure

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

Thermostatic Expansion Valves

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

Electronic Expansion Valves

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

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Subcooling

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

Related Articles:
Air Cooled Chiller Planned Maintenance

Water Chiller Maintenance

Process Chiller Maintenance Visit

Chilled Water System Maintenance

Centrifugal Chiller Maintenance

Industrial Chiller Maintenance

Air Cooled Chiller Condenser Maintenance

Glycol Chiller Maintenance

Chiller Maintenance Schedule

Air Cooled Chiller Maintenance

Chiller Maintenance Company

Chilling Plant Maintenance

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

Further reading on the subject of preventive maintenance on Wikipedia


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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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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Read more about reducing refrigerant leaks at the Institute of Refrigeration


Frost covered blue oil return vessel during the removal of industrial refrigeration sludge

Industrial Refrigeration Sludge

This industrial refrigeration visit is to remove sludge from the system. There had been a long period of neglect prior to Maximus Chillers attending site, so regular oil changes had not been carried out. Two oil changes have now been carried out and still a small amount of sludge remains in the system.

Industrial Refrigeration Sludge Removal

Due to previous sludge removal, the plant was down to about half of its 60kg charge of refrigerant. It was starting to show signs of refrigerant shortage as the machine was preventing loading up. An ammonia suitable pump out unit was used to decant the remaining refrigerant into a cylinder for disposal.

Pressure and Temperature

Once this had been carried out, any residual refrigerant in the oil and liquid on the low side of the plant was carefully handled until the plant was at the same pressure and temperature of the surrounding environment. See picture of some remaining liquid boiling off in an oil return vessel on the bottom of the flooded evaporator.

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Industrial Refrigeration Oil Sludge

Once the pressure and temperatures equalized, our engineer drained the oil in the system from four different vessels. The oil was then removed from site for recycling. Usually, pressure helps with the process, but as the system was empty, gravity was sufficient for most parts of the plant. Nitrogen being introduced to the oil supply pipe to push it back to the oil separator.

Flushing Agent

A flushing agent specially formulated for use in ammonia systems was used to aid the removal of sludge and oil from the pipework around the chiller.

Evacuation

After a pressure test, the evacuation process was started. This was to boil off any remaining flushing agent, to remove non condensables and remove any moisture. A near perfect vacuum was achieved.

Run up

New refrigeration grade anhydrous ammonia was charged into the system, a little at first to check for any leaks. Then, the plant was checked for effective running conditions. All readings were okay with the compressor loading up to 100% before backing off to match the load.

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Read more about ammonia systems oil draining at the Institute of Refrigeration


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