Air Cooled Chiller Superheat Maintenance

Vacuum pump and green compressor during air cooled chiller superheat maintenance

Air Cooled Chiller Superheat Maintenance

Air cooled chiller superheat maintenance at Maximus Chillers. During the visit, we found a high superheat condition with an Italian chiller. The customer had reported a low refrigerant charge trip out. The customer raised the order, so we got straight to work on the leak during the maintenance visit.

Pressure Temperature Relationship

Put simply, the higher the pressure, the higher the temperature of the refrigerant- this is consistent with Charles’s Law of Constant Volume. The refrigerant was found to be at a higher temperature above saturation (or boiling point) than usual- which is a high superheat condition. The chiller runs on R134a, which is a HFC refrigerant.

Air Cooled Chiller Superheat Maintenance with Leak Finding

Our engineer used his leak identification equipment to find the leak. After looking around the chiller he found the leak adjacent to the shell and tube evaporator, where 4 bolts hold the suction pipe on. This coupling is sealed with a gasket.

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Chiller Pump Down

Because of the location of the leak, our engineer decided to pump the chiller down to the condenser and valve the evaporator off. A lot less time consuming than setting up the recovery unit to decant the refrigerant.

Air Cooled Chiller Superheat Maintenance with Leak Repairs

He used his Allen key set to remove the suction pipe from the evaporator. On inspection, the paper gasket had deteriorated then been pushed out by the pressure in the system. All of our engineers carry an extensive range of commonly used parts and materials as standard in their cars. This is to reduce down time for the customer. He made up a new paper gasket, coated it with a special sealing compound, then re fitted the suction pipe to the evaporator. He then used his torque wrench on the Allen key bolts to the correct manufacturer’s recommendations. The system was then pressure tested and dehydrated as per standard industry guidelines.

Screw Compressor

The superheat value at the Bitzer screw compressor was found to be within normal operating values after additional refrigerant was added to the system. A further follow up leak test was carried out at a later date according to F-gas regulations. The paperwork being kept in the F-gas file in the chief engineer’s office.

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

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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 during packaged chiller service 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° 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 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 | Click Here


Green Bitzer compressor being vacuumed during HFC chiller service

HFC Chiller Service

The HFC chiller being serviced in the photo is 600kw. It consists of two systems with a large Bitzer compressor for each system. It has a bespoke Micro Control System front end to run the machine and stop it should there be a fault condition. The chiller had been reported by the customer to have tripped out on a low pressure fault.

HFC Chiller Diagnosis Service

The readings of superheat and subcooling are available in the controller of the HFC chiller being serviced. This removes the need to fit instrumentation carried by our engineers. The process of diagnosis was therefore speeded up. The result being that the chiller was found to be running short of refrigerant.

Return Visit to Decant the Refrigerant

A Quote was submitted to the customer for approval. Once the Order was raised, a convenient time was arranged to return to site and carry out the HFC chiller service. The remaining charge of refrigerant was decanted into our recovery vessels with one of our fast pump out units which are carried by each of our engineers.

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Looking Around the Pipework for a Leak

Nitrogen, an inert gas, was introduced into the system to assist in the location of the leak. The leak was quickly found on one of the end turns of the condenser.

Brazing and Pressure Testing

Our engineer made good the leak using his brazing torch. Then, the integrity of the system was proven to industry standards with a system pressure test.

The Evacuation Process for HFC Chiller Service

The picture shows a 10 cfm (cubic feet per minute) vacuum pump being used to dehydrate the system during HFC chiller service. Each of our engineers carries a vacuum pump of this capacity as it speeds up the process. One refrigerant hose being fitted to the discharge pipe and another, smaller hose being fitted to the suction pipe. The system being vacuumed to a deep vacuum.

Recharge and Run Testing

After the chiller had been recharged with some of the charge of the refrigerant R134a, the remaining refrigerant was charged in its liquid phase, away from the compressor, until the superheat and subcooling values were within industry limits. A large amount of load was available as the chiller feeds an air blown film plastic manufacturing facility.

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Mirror looking for leak during chilled water system EEV service

Chilled Water System EEV Service

Chilled water system EEV service was being carried out because the mechanical parts had failed. This particular valve is prone to this fault. It is an OEM part so our technician found the voltage for the motor and found a similar part with the same amount of steps.

Chilled Water System EEV Service

The EEV driver was found to be functioning satisfactorily during the chilled water system service. Sometimes, depending on how the mechanical part of the EEV has failed, the driver can be overloaded and burned out.

Electronic Component Refurbishment

Where electronic parts, such as the EEV driver, are found to be burned out- Maximus Chillers has a refurbishment laboratory at head office. We have the capability to strip down the component and fault find where it has blown. Usually it is quite simple: the jammed mechanical part of the electronic expansion valve has burned out the power control on the driver for example. More complex fault finding and component replacement on the circuit board can be carried out also. Another option is to replace the driver with a like for like swap or retrofit to a different driver.

0161 370 7193

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Pump Down for Chilled Water System EEV Service

The chiller was pumped down and valved off. This saves on the time and recovery vessel to pump the refrigerant out.

Remove and Replace

Once pumped down, our engineer removed and replaced the valve, sealing it on it's knife edge seal. The wire was passed up the conduit and into the panel. The wiring colour scheme was different on the new valve, so some time was taken to ensure it was wired up correctly.

Open it up and Switch it on

After leak testing, the refrigerant system valves were opened back up and the plant switched back on. The correct superheat and subcooling valued were achieved concluding a successful chilled water system service visit.

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To read the Institute of Refrigeration guide to expansion valves Click Here


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