In this month’s troubleshooting situation, our problem involves a 4-pin compressor that uses both an internal and external overload protector. Two other factors in regard to this particular piece of equipment are: A single-pole contactor is used in the compressor circuit, and it is equipped with high and low pressure switches that act as protective devices.
In this troubleshooting situation, the equipment is a walk-in refrigeration system in a busy restaurant that has experienced a compressor failure…specifically a mechanical failure.
Compressor burnout is a very specific mode of failure that may be caused by high temperatures in the motor windings or discharge area of the compressor.
Ninety percent of compressor failures can be attributed to problems found elsewhere in the system. And, serious consequences can result if technicians don’t determine the true source of the compressor failure.
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.
Should a compressor fail, the entire system will fail, and knowing how to properly test, diagnose, troubleshoot, and maintain that equipment will ensure minimal downtime while preventing future failures.
Bob and Tim were on their way to a no cooling call. The spring season was still cool at night and warm in the daytime. The customer told the dispatcher, “The unit started up at about 10:30 a.m. this morning and made a noise, but did not cool the house, even though it is still running.”
Compressor overheating is usually caused from high compression ratios. High compression ratios can be caused from a combination of high condensing pressures (temperatures) and low suction (evaporating) pressures.