Category Archives: Chiller Components

6 green Bitzer scroll compressors being maintained in a chiller

Scroll Chiller Compressor Maintenance

Here at Maximus Chillers, we carry out scroll chiller compressor maintenance to extend the lifespan and reduce downtime to your critical plant. This planning ahead is central to how we do things- we resolve small problems before they become big problems. Having the capability to do anything is part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere.

How they Work

The refrigerant vapour passes in between two scrolls (spirals) One of these is fixed, the other orbits backwards and forwards against the fixed scroll using a swing link. This creates a series of crescent shaped gas pockets in between the scrolls. These gas pockets get smaller in size as the refrigerant travels from the suction at the edge, down the spirals to the discharge at the centre. It then leaves downwards through a port. There are check valves to prevent back feeding of refrigerant during off cycles when other compressors on the same system are still running.

Advantages

There are several gas pockets occurring at any one time through the scroll, therefore giving a smooth and continuous compression cycle. Other advantages are low internal friction resulting in a quiet operation and low vibration levels. These low vibration levels help to lower the occurrence of leaks around the compressor.

Oil Level during Scroll Chiller Compressor Maintenance

The correct oil level is noted on our detailed Tick Sheets for all of the compressors. This record helps with the diagnosis when things start to go wrong. We can look for a pattern where the level starts to drop off in the compressors on a particular system, then look at the other readings which may be the cause.

Oil Samples during Scroll Chiller Compressor Maintenance

At periodic intervals, we take oil samples which we analyse in our laboratory at Head Office in Droylsden. We look for white metal, coloured metal, refrigerant composition, acid and sludge. This means that we can notice, then resolve system issues before a costly compressor failure occurs.

Oil Changes during Scroll Chiller Compressor Maintenance

This kind of compressor is fitted with a service port for the draining and filling of oil. The correct procedure is followed due to system pressure being present inside. We then carry out the oil changes using our specialist oil handling tools. Our skilled engineers carry the correct PPE for the work being carried out. We also we provide Risk Assessment Method Statements for each job.

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Crank Case Heaters

In the photo you can see the silver band of the crank case heaters at the bottom of the compressors. They keep the oil at the required temperature so as to not cause compressor wear on start up. The heaters also have the effect of ensuring that the refrigerant cannot condense into liquid during cold weather. As a compressor cannot compress a liquid, compressor failure would occur. A normally closed contact on the delta compressor starter contactor usually runs the heater: it drops out when the compressor starts. The function of all of these heaters is checked on each maintenance visit.

Discharge Temperature

It is critical that the discharge temperature is not too high, as this is the cause of the refrigerant breaking down into acid and sludge as previously mentioned. The acid rots the insulation on the copper windings inside the compressor. When this has occurred, an electrical failure will result in the compressor, causing the fuses to blow and a fault condition on the chiller. Compressor swap out is the cure which is expensive and inconvenient. We take the discharge temperature readings during the maintenance so as to fault find the cause.

Suction Pressure

Adequate suction pressure is needed to ensure good oil return to the compressor and prevent low pressure trips. As the refrigerant entrains the oil around the system, a good mass flow rate is needed, or the oil will just ‘pool’ in the bottom of the evaporator. Poor oil return will result in a seized compressor. Therefore, particular attention is taken to the low pressure gauge by our engineers. System adjustments or recommendations are made to ensure the seamless operation of your plant. If system overhaul is required, a Quote will be submitted at the end of the visit.

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Compressor Holding Down Bolts

There are usually four of these on each compressor. They fit though a steel sleeve which, in turn, fits through a rubber mount. The whole assembly is bolted into the frame of the chiller. The function is to securely hold the compressor in place and to dissipate vibration. We check the tightness is correct with our torque wrenches and change the rubbers periodically. A compressor rattling around uncontrollably, especially during start up and stopping causes catastrophic leaks around the compressor. This usually leads to the whole, or the most part of the refrigerant charge being lost to atmosphere.

Motor Protection Module

A resistance sensor embedded in the compressor windings plugs into this module on the S1 and S2 terminals. The fault feedback to the controls is on the M1 and M2 terminals. The power supply to the module is on the L and N terminals. When the windings start to get hot, the module detects this after a pre determined level of resistance is reached. The M2 terminal opens and volts drop out to the relay board, then a lower volt control signal drops out to the controller. We check the sensor resistance and compare it to a chart to ensure it is within the allowable range on each visit.

Wire Tightening during Scroll Chiller Compressor Maintenance

We waggle the motor connectors and check for any cracking to the wires which may lead to an earth sort out. We tighten the wiring on the compressor starter contactors and check the condition of the contactor contacts. These become ‘splattered’ causing an uneven amount of amps to the compressor. This volt drop causes the contactors to fail and will eventually cause compressor motor failure. We change the contactor contacts from our range of parts at Head Office.

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Grey shell & tube chiller evaporator being maintained with centrifugal compressor above

Shell & Tube Chiller Evaporator Maintenance

With shell & tube chiller evaporator maintenance to be carried out- it was time to sign the permit to work and get going. There are 5 chillers in total, but 1 of the chillers had been dismantled by the previous company and is unlikely to run again. This left 4 flooded systems to be maintained while the factory was still in production. Therefore, it had been decided in the Method Statement that one chiller would be done at a time. The plant had been designed with N+1 in mind, as it is critical not to loose the process- causing a factory shutdown. This means that so long as 2 of the chillers are running, there will be no loss in production. With 1 chiller out of service and another being worked on, this left 3 chillers in operation. If 1 were to fail, then there would still be the minimum of 2 left running.

Hire Chillers

In the unlikely event that 2 of the 3 chillers left running were to fail, an action plan was in place to lift in 1 MW of hire chillers.

Pump Sets and Hoses

The hire chillers would come with 2 engineers to pipe the pump sets into the onsite water system. This water system has been designed with this in mind so ‘stab ins’ have been built into it with shut off valves for the connection of temporary hoses.

Vanes

The chilled water is close control with a critical 6° to 8° set point. The chillers in the photo are very good at achieving this close control as they use vanes on the inlet to the suction. These vanes can be adjusted from anywhere between fully closed, with a small amount of bypassing, to fully open.

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Buffer Vessel

The hire chillers, on the other hand would not be close control. They would be multiple system chillers with various stages of loading on each chiller. One 600 kW chiller and another 400 kW. Each of the chillers onsite are 1.3 MW, but as they never run at 100% the onsite maintenance manager agreed to the proposal. It is unlikely that this plan would be needed, but planning for it is critical. A 10,000 ltr buffer vessel was decided upon to make the hire chillers close control. The chillers discharge into the buffer vessel, then the water mixes around before returning back to the chillers. The process water too being discharged into the buffer vessel before returning to the process. The position of the inlet and outlet on both water systems being strategically decided upon to ensure a steady exchange of heat and a smooth water out temperature back to the process.

Valve off and Drain Down

The Water In and Water Out pipes were valved off and the contents of the evaporator drained down. There was no glycol or chemicals in the water system which made the job easy. Otherwise, the water in the evaporator would have to have been pumped into vessels for disposal.

End Plate Removal during Shell & Tube Chiller Evaporator Maintenance

The lift and shift team were on site to assist with the removal of the end plate. After the bolts were removed, they attached their lifting eyes and straps, then lifted the end plate to the side.

Evaporator Cleaning 

We have in our stores a specialist evaporator cleaning tool. After a period of time, the evaporator tubes become fouled with impurities picked up from the water system. Also, contaminants get in from the air into the water tower. The strainer has some effect, but thermal insulation builds up on the water side of the tubes. It prevents latent heat being absorbed into the fridge system from the process. After the cleaning process, the efficiency of the copper tubes was increased to the same level as when the chiller was new. This is part of what we call the MAXIMUS ADVANTAGE Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. 

Reassembly after Shell & Tube Chiller Evaporator Maintenance

The seal was replaced from our range of seal sizes, on the shelf in our stores. The reassembly being the reverse of the strip down, the lift and shift team aligning the end plate for refitting on guide runners. It was then tightened to the correct torque setting. A little at a time, the water system valves were opened until full flow and water system pressure was achieved. No leaks occurred, so it was time to go on to the next phase of the job…

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Run Up after Shell & Tube Chiller Evaporator Maintenance

After bringing this chiller back online, it went through a timer, then loaded up steadily to 68%. The refrigerant system readings had been taken previously, so they were compared to the readings taken after the job. A lot more heat transfer being achieved with more latent heat being absorbed from the process.

Remaining Chillers

The above mentioned process was repeated to the remaining chillers one at a time. No issues were encountered and the whole job proceeded steadily to completion.

Compressor Loading

The load from the factory is very steady, so each time another chiller evaporator was cleaned, the row of chillers would unload slightly. They were running at 72% on arrival, then 68%, then 63% then 59%. This was demonstrated to the customer as a visual way of proving how we had improved the efficiency of his plant. Compressor unloading uses less electricity, so lower carbon emissions and a lower electricity bill are the direct result of our maintenance. Also, kilowatt hour meters are linked to the maintenance manager's computer for monitoring.

Shell & Tube Evaporator Chiller Maintenance Tidiness

As with al of our jobs, the work location of the chillers was left in a better condition than when we arrived. Any waste and unused items being recycled or returned to the stores on site or the stores at our Head Office. The chillers being wiped down and the end plates re painted. With regular maintenance, we at Maximus Chillers will take years off the life of your plant. It is not unusual for us to keep this kind of plant running for more than 50 years.

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Green Bitzer screw chiller compressor with oil separator removed on bench in our workshop

Screw Chiller Compressor Maintenance

Open Drive Screw Chiller Compressor Maintenance

Open drive screw chiller compressor maintenance involves changing the shaft seal at intervals or if it leaks. This kind of compressor is used with ammonia as this refrigerant corrodes the copper windings and the insulation. It is also used with most large HFC (hydrofluorocarbon) and HFO (hydrofluoroolefin) chillers.

Semi Hermetic Screw Chiller Compressor Maintenance

Because all of the components are internal, this kind of compressor needs less maintenance. It is most often used with smaller chillers running on HFC and HFO refrigerants. This is the compressor type featured in the photo.

Matched Helical Rotors

This kind of compressor design uses a matched pair of helical rotors. These are accurately machined so as to trap, then compress the refrigerant as it travels along the screw. Oil injection is used to create a seal between the rotors. The two rotors are different in shape: the male rotor is driven by the motor and usually has 4 lobes. The female rotor meshes with male and usually has 6 interlobe spaces. The cylinder casting around the rotors is equally important as it seals in the vapour along the screw. Both rotors are helixes with the male rotor moving more rapidly. This compressor design provides a continuous pumping action, rather than pulsating as with a reciprocating compressor. Another advantage of this kind of compression is that there is very little vibration. Indeed, you can place a coin, on its side, on top of the compressors we look after and it does not fall over. This lack of vibration helps to prevent refrigerant leaks around the compressor.

Single Screw with Gate Rotors

This kind of compressor design uses one main rotor meshing with 2 star gate rotors. These are at right angles with the main rotor. The main rotor usually has 6 grooves.

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Screw Chiller Compressor Maintenance and Reliability

Both of these compressor designs are very reliable with a long bearing life. A maintenance free lifespan of 30 years for the bearings is not uncommon. It is quite common that the compressor will outlive the chiller. In the unlikely event of bearing wear, a characteristic is for there to be undue noise from the compressor at part load which goes away at full load. Higher oil temperature and an unsatisfactory oil analysis are also indicators.

Slide Valve

The capacity is seamless as it is regulated with a slide valve. A spring returns the valve to the unloaded position and a gear type oil pump gives above discharge pressure to load it. The oil pump is not for lubrication, it is just to give the valve enough force to slide with the discharge pressure acting against it. A slide valve potentiometer is fitted to a sliding rod on the end of the valve. It translates the movement along this rod into usually 4-20mA. This signal feeds back to the controller which converts it into a percentage loading reading.

Lubrication during Screw Chiller Compressor Maintenance

Pressures and temperatures are taken during the maintenance to ensure seamless operation. The oil sump is usually inside the base of the oil separator which is at discharge pressure. An oil return pipe is available from the oil sump to the suction side of the screw. Because of the pressure difference from discharge to suction, the oil naturally lubricates the compressor without any need of an oil pump. The oil lubricates the bearings and is injected with the refrigerant along the screw. This provides a seal between the rotors or gate rotors, it also lubricates the rotors to prevent excessive wear.

Oil Separator

The oil enters the oil separator after being discharged with the refrigerant from the compressor. This vessel is insulated so as to stop refrigerant condensing inside as it would in the condenser. An oil heater keeps the oil at the optimum temperature for the compressor. This heater also prevents liquid from forming in the oil separator during off cycles. A check valve on the outlet also prevents this from happening by stopping the migration of refrigerant from the condenser. As the oil sump is the oil supply to the compressor, a temperature sensor will make the program lock the compressor out, should the oil be too cold. This is usually because the main power supply to the chiller has been off during maintenance. The larger volume inside the oil separator slows the speed of the refrigerant so as to allow the oil to drop out. A common design is for the discharge to be directed to the top of the vessel, with a spiral going down to the sump. The oil falls out of the refrigerant vapour during this process. For additional oil recovery, the oil goes up through finer and finer layers of mesh. The oil sticks to this mesh and runs down in to the sump.

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Oil Return

Small amounts of oil that have escaped the oil separator will end up in various vessels around the system. On smaller HFC systems there is less of a problem as the oil is entrained by the refrigerant, round the system and back to the compressor. In larger, flooded HFC systems, the oil mainly ends up in the bottom of the evaporator. For ammonia systems, the oil does not entrain with the refrigerant so oil return devices must be used.

Eductor

This is a pot at the bottom of the vessel where the oil collects. At periodic intervals, discharge gas is blown across the top of the oil which has collected. This has the effect of picking it up and carrying it into the suction of the compressor.

Periodic Oil Changes

We at Maximus Chillers have the full range of refrigerant grade oil for all refrigerant types. It is part of what we call the MAXIMUS ADVANTAGE™ Any Chiller- Any Problem- Any Part- Any Refrigerant- Anywhere. It is critical that the correct oil is selected otherwise compressor failure will result. During each maintenance visit, we make a note of the compressor run hours and carry out oil changes at the correct intervals.

Oil Analysis

We take oil samples which we analyse in our laboratory for signs of compressor wear, oil quality and contaminants. This way, we can prevent untimely compressor failure. If one of your compressors were to fail, however, we have a remanufacturing facility and a lift and shift team to get the job done fast! 

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Chiller compressor failure of blue Grasso in enclosure

Chiller Compressors

System Testing for Chiller Compressors

Chiller compressors fail often the result of ineffective servicing and system testing. At Maximus Chillers, we carry out extensive tests during our visits to ensure that small problems are resolved before they become big problems. If we notice a reading starting to become abnormal, we can carry out the diagnosis, then do the necessary service. Some of the compressor readings we monitor:

Compressor Temperature

The suction, discharge, motor windings and bearing temperatures are recorded for comparison to previous visits. These are often available in the PLC for the chiller, or our engineer can take the readings with his test equipment. Problems with the oil cooler can be the cause of higher compressor temperatures, the system running outside of its nominal operating conditions is another reason. Magnetic drive systems have an advantage as they do not use oil.

Accelerometer

Portable vibration sensors are carried in of each of our company vehicles. This is an accelerometer to measure vibration. Along with other system readings, we keep an on going record of the vibration levels around the compressor. When internal components are coming out of alignment due to wear, this causes an out of balance condition in the compressor. This, in turn, causes a knock on effect- causing other components to go out of balance. Catching this condition early will prevent a compressor smash up resulting in the replacement of expensive internal components.

Oil Analysis

Another way of preventing big problems to occur is periodic compressor oil testing. Samples are taken, usually on alternate visits, which are sent off to a laboratory for analysis. The acid level is tested to provide pre warning of a potential compressor motor windings burn out. This is because acid in the compressor oil rots through the electrical insulation on the motor windings. The presence and quantity of white metal and yellow metal is analysed too. This is a window through to a component starting to wear inside the compressor.

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Screw

The compressor in the photo is a screw compressor. It operates with ammonia refrigerant. This refrigerant is usually used for low temperature applications, mainly associated with food production. This compressor, however, has a 1° refrigerant saturation and is used to cool computer rooms. Common causes of compressor failure on this kind of compressor are:

Leaking Compressor Castings

The various compressor components are sealed together using ‘o’ rings or paper gaskets. ‘O’ rings are especially prone to leaks due to work hardening and flattening of the sealing face of the ‘o’ ring. The system can be pumped down and the compressor valved off. Then, our lift and shift team can remove the compressor to our remanufacturing facility for strip down.

Leaking Shaft Seal

The mating surface of a shaft seal has a mirror smooth finish. This is to reduce friction and aid with a better seal. Over time, this starts to wear, causing an ineffective seal and a leak of refrigerant and oil. A service visit can be arranged to change the shaft seal on site. The shaft couplings can be split, the shaft seal can then be removed and replaced. A quick job, then the machine is up and running again.

Slide Valve Potentiometer

This is an electronic device with a slide attached to the moving compressor slide valve. The device has a start and an end position programmed into it during commissioning. The potentiometer converts the slide valve position, usually into a 4-20mA signal which is fed back to the chiller PLC. They are prone to reading out or the reading being jammed in one position. This results in a trip out from the controls, as the controller is not able to determine the true position of the compressor slide valve. We have an off the shelf stock of slide valve potentiometers for the various compressor range. A service visit can be arranged to replace the part after diagnosis has been carried out.

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Centrifugal

Centrifugal compressors are a very reliable kind of compressor but when they go wrong, they can go wrong in a big way. Compressor overhaul is expensive, this can be carried out onsite, or a better option is a lift and shift to our remanufacturing facility. Proximity sensors are usually fitted to monitor the distance between the impeller and the casting. This is an added protection along with the other sensors and transducers around the compressor.

MCS

We are on account with Micro Control Systems- an American company who specialise in building panels to order for specific chiller compressors. We easily fit this control system to any compressor to control the loading of the vanes in accordance to the available load from the process. The control panel has previously been fitted to other machines of the same model number, so any teething issues have already been ironed out. Maximus Chillers can achieve seamless operation of your plant.

Oil System for Chiller Compressors 

Newer centrifugal compressors are oil free so as to eliminate any of the service issues relating to oil. There are a substantial amount of compressors, however, that use oil to lubricate the bearings. This kind of compressor, if properly serviced, can last for 50 years. The oil system picks up impurities which are caught by various filters. These filters can be changed or cleaned according to the prescribed service schedule. Our engineers make sure that spares are ordered and kept onsite prior to a visit.

Cost Effective

Our visits and ongoing upkeep of your plant saves money. Money spent as a preventative measure saves so much more money in the long run. With competitive prices on specialist internal compressor parts- Maximus Chillers completes the picture. When compressor failure occurs, you are in safe hands with years of industry experience invested in each of our engineers.

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Scroll

These are some issues affecting a scroll compressor:

High Discharge Pressure

With high discharge pressure, there is a corresponding increase in discharge temperature. This means that the compressor is operating beyond its recommended values. The cause of this is often a poorly maintained condenser. Especially on industrial chillers, there can have been gaps in the schedule where the condenser was not correctly serviced. This condition is often rectified easily by an onsite engineer by giving it a brush down. Where the fins are bent over- we carry a specialist tool to straighten them back out- how they came out of the factory. We also use different formulas of chemicals to rinse the various kinds of dirt from deep within the fins.

High Suction Pressure on Chiller Compressors 

Some chillers are used where very high water temperature can come back from the process if the chiller were to be off line for a short period. Usually, this happens in factories where certain industrial processes are being carried out. When the onsite engineers start the plant back up, the chiller experiences a high heat load to deal with.

MOP Expansion Valves

Maximum operating pressure expansion valves limit the pressure in the evaporator to a given level, regardless of the available heat load from the process. They do this by having a limited amount of liquid refrigerant in the bulb. When this runs out, the power element cannot push the orifice open any further- thus limiting the suction pressure. This is important to prevent scroll compressor failure as it prevents putting added strain on the compressor motor windings due to high suction pressure.

Oil and Refrigerant Shortage

Where there is a shortage in refrigerant, there follows a low oil level condition. The refrigerant mass flow rate, carries the oil around the system and back to the compressor. This is greatly impaired when the chiller is short of gas. The oil cools the compressor and lubricates the shaft bearings. These bearings and other internal components wear down and seize causing failure. Maximus Chillers can put together a package to minimise chiller compressor failure.

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Yellow oil drums, ammonia refrigerant cylinders and flammable flushing agent of chiller parts supplier

Chiller Parts Supplier

Chiller Parts Supplier of Compressors

Centrifugal

As a chiller parts supplier, all kinds of centrifugal compressors are remanufactured in our workshop. With an over head gantry crane and specialist equipment to hand- Maximus Chillers completes the picture.

Screw

Screw compressors are remanufactured on the bench. With compressed air and bearing tools- our skilled screw compressor technicians are seasoned in high tolerance measurements.

Scroll

We have a range of off the shelf Copeland compressors for a fast lead time on process chiller repairs.

Chiller Parts Supplier of Condensers

Air Cooled

When the condenser on an air cooled chiller is in poor condition- our site survey team will attend to measure up for a new bespoke condenser.

Shell and Tube

This type of condenser is used on water cooled chillers.

Chiller Parts Supplier of Evaporators

Shell and Tube

This is the most popular type of evaporator for large chillers. The low temperature refrigerant is on the outside of the tubes in liquid form. The water is pumped through the tubes, releasing heat from the process into the refrigerant. This is latent heat as the liquid refrigerant boils off into a vapour.

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Chiller Parts Supplier

Vibration Eliminators

We have all the sizes of anacondas on the shelf in our stores. This saves on the delivery time to site when your process if off due to the chiller. Maximus Chillers will get you up and running- fast!

Flushing Agent

For when things go wrong… we stock a solvent based flushing agent which is blown through the system with nitrogen.

Refrigerant Economizers

These are another term for a subcooler. If the refrigerant is further subcooled after the condenser- the system will run more efficiently.

Chiller Parts Supplier of Controls

Pressure Transducers

We can make temporary repairs to faulty pressure transducers using our test equipment. This will keep your plant running while the part arrives onsite.

Chiller Parts Supplier of Ammonia and HFC refrigerant

A full selection of refrigerants are available in our stores including: anhydrous ammonia, R407c, R134a and R410a.

Chiller Parts Supplier of Compressor Oil

Low, medium and high viscosity oils in 5ltr cans and 20ltr drums are ready for shipping from our storage area.

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

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

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.

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° 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 maintenance click the Tag at the top of the page.

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

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