Compressors, like everything else that is man made, can fail, and replacement usually comes at a very high cost. “Compressor failure”, however, cannot be considered a diagnosis in-and-of itself. In an estimated nine out of ten cases, compressor failure occurs as a direct result of issues found elsewhere in the system. If a compressor is replaced without determining and correcting the root cause of the failure, the new equipment is extremely likely to fail as well.
Lack of lubrication is the single most common cause of compressor failure, and there are a number of root causes for oil loss. One problem that can lead to lubrication issues is incorrectly-sized piping on split systems, which can trap oil and prevent it from returning to the compressor properly. Suction lines must be large enough to minimize pressure drop, but small enough to maintain required velocity for oil return. Liquid lines must be large enough to minimize pressure drop and small enough to avoid underchanging the system. The best way to ensure that piping is properly sized is to follow factory guidelines for piping and accessories.
Floodback is a problem that occurs when liquid refrigerant returns to the compressor through the suction pipe during the running cycle, washing oil from bearing surfaces. This dilution can lead to excessive wear in bearings, pistons, cylinders, rotors, and stators. Flooded starts result when refrigerant migrates and condenses in the crankcase oil during the off cycle. On startup, crankcase pressure drops and the refrigerant bursts from the oil, carrying oil out of the crankcase and washing oil from bearings, journals and rods. Both flooding and floodback are caused by a large variety of issues.
Another common compressor-killing issue is slugging, which occurs when a mass or “slug” of liquid refrigerant or oil (or both) returns to the compressor, usually on startup. Since compressors are designed to compress gas, not liquid, slugging usually results in damaged components that lead to equipment failure. Slugging can be due to a number of root causes.
These are only three of the multitude of reasons why compressors fail, and a defect in the equipment itself is rarely the case. Again, compressors should never be replaced without first determining and fixing the cause of failure, which requires an expert contractor like PJM.
PJM Mechanical Contractors, Inc. is a multi-faceted mechanical contractor providing construction and installation, service and maintenance, and design/build services in a comprehensive range of mechanical disciplines that include HVAC, plumbing, controls, refrigeration, custom metal fabrication, piping, fire protection, and backflow preventer testing. PJM primarily serves clients in pharmaceuticals, manufacturing, healthcare, institutional, and other various commercial and industrial sectors.