When a compressor fails on a piece of refrigeration equipment, determining that it failed and identifying its replacement are relatively simple and common procedures. Discovering why the original compressor failed, on the other hand, may not be as simple. However, it’s extremely important for the service technician to do so. Replacing a defective compressor without finding the cause can surely cause the replacement compressor to fail. Replacing the compressor a second, third, or fourth time is not advantageous to the service contractor or to the customer. It can cause the service contractor to lose money and, quite possibly, lose the customer, too.
Replacement compressors fail at a much higher rate than compressors used on new systems, which indicates there is most likely a system issue that causes a replacement compressor to be needed in the first place.
In most cases, it’s difficult to determine what caused the compressor to fail before the compressor has been replaced. The compressor is not normally running, and the system is not refrigerating. However, after replacing the compressor, the technician should spend time diagnosing why the original compressor failed. Usually, with a detailed inspection, the technician should be able to find the cause. The inspection should include checking the running suction and discharge pressures, the temperature of the returning refrigerant, the amount of superheat at the inlet of the compressor, the compressor’s amperage draw, and its applied voltage. Comparing these readings to the manufacturer’s specifications will help identify the cause of the failure.
Some typical causes of a compressor failure are liquid returning to the compressor, high return gas temperature, high discharge temperature, or incorrectly applied voltage to the compressor. Most of these causes can be found once the compressor is up and running.
There are times, however, when the apparent cause cannot be found upon startup. The technician should then monitor the system’s operation for a period of time so the cause can be determined. The problem may develop after the system has been running for some time — for example, during or after a defrost cycle or as a result of an iced evaporator coil.
Another helpful troubleshooting tool is to disassemble the defective compressor and examine the valve plates, pistons, crankshaft, bearing surfaces, and windings. This can help immensely in identifying or confirming the cause of the original failure. Although this is a time-consuming step, it’s well worth the time and effort.
It’s also helpful for the technician to speak with the customer to gain the system’s operational history. Discovering if the compressor has been replaced prior to the tech’s involvement or if there has been any other major work done on the system will aid in finding the cause.
Preventing repeat compressor failures is a must for any successful service contractor. Not only do repeat failures take away from the contractor’s profit margin, they also tarnish a company’s professional image. Finding the cause and repairing it not only keeps the customer happy, it keeps the contractor profitable.
Publication date: 11/2/2015
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