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Replacing An Air Conditioning Compressor

By: Philip Hamer, Sat May 29th, 2010

Replacing the compressor in an air conditioning unit is a job for an air conditioning maintenance engineer. The electrical supplies to both the outdoor and indoor units should be isolated for safety. The refrigerant will need to be removed from the system using a refrigerant recovery machine which will transfer any refrigerant into a service cylinder for recycling. It is best to replace the refrigerant as it will contain acids caused from the compressor burn out. The recovery machine is connected to the air conditioning unit via a service manifold. When the recovery process has been completed all of the refrigerant will have safely been removed from the system. Most refrigerants are ozone depleting substances and should be handled carefully with minimal release to the atmosphere. The external panels of the unit are removed to gain access and in some cases most of the internal components such as circuit boards and contactors are removed. A suitable point is chosen to cut the copper pipes feeding the compressor and a circular pipe cutter is used to make the cut. After disconnecting the electrical wires and retaining fixings the compressor can be removed. The remaining pipe stabbings are removed using a high temperature brazing torch. Oxygen free nitrogen is purged through the pipe work whilst it is heated to prevent scale build up within the pipes. Scale build up breaks down into small flakes which can damage the new compressor. The copper stabbings are cleaned and brazed to the new compressor in the same orientation as they were removed. The compressor is then fixed back into the unit and the pipe work brazed back together with copper fittings. A line filter is installed to the suction line close to the outdoor unit directly into the pipe run. If the unit contains a heat pump make sure that the filter can be used in both directions. A pressure test would then be carried out generally to around 400 psi with oxygen free nitrogen. Leak detector spray is applied to all brazed joints to check for a leak. If there is no change in pressure over a duration of 24 hours then the brazing was carried out successfully. All components can now be fitted back to the unit and the wires connected back to the compressor. The system would be vacuumed down for at least 2 hours then new refrigerant can be charged back into the system. We would always introduce an 'acid shot' to the system with a special tool. The acid shot is poured into a special injector which can be connected to the refrigerant lines. It is briefly vacuumed to remove condensable gasses and then connected between the high and low sides using the engineers manifold. The unit can then be operated for the first time and the acid shot is forced into the system by briefly joining the high and low sides via the manifold. The acid shot will cause any acids within the system to be retained in the filter previously installed. The unit is inspected whilst running to ensure the compressor is working correctly and a leak detection test carried out with an electronic leak detector.

Magma Energy Services Ltd specialise in air conditioning installation, air conditioning repair and air conditioning maintenance.

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