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User Portal Sign in Register. Thermal Discovery Center ThermalTools. View Recorded Webinars. Learn More. Our people make the difference. Service And Support. View Locations. Foreign Particles Due to handling. Fill the compressor crankcase from a known-good source of lubricant. Always use an oil specified by your service manual.
Use clean rags and fill from clean containers when adding lubricants. Always use an oil pump to replace the oil, using good techniques such as making sure there is a solid hose of oil no bubbles from the pump. Charge your refrigerant loop from a known-good source of gas. If a refrigerant or lubricating loop must be opened, be sure it is protected from contamination and is clean when re-sealed.
Due to operation. Common causes of contamination: Chips from broken reed valves Dirt from the casting process used for the compressor body, heads, and other cast iron components. As expected under such circumstances, the new compressor will eventually fail as well at rate several times higher than for original installation.
For the majority of compressors, which do not fail in 15 years, there must be a condition of part variation that withstands all of the applied operating conditions. Other compressors with more serious variations eventually experience the operating condition that will cause failure. Compressors, operated within their limits, do not wear out. In one documented instance, a compressor ran more than 30, hours and 16, cycles.
When it was subsequently torn down and all its parts were measured, they were found to be still within new compressor specifications and tolerances. Then why do compressors fail? Two extreme cases may lead to a general conclusion. First, a compressor can be subjected to abusive conditions, such as a harsh tropical environment. Extremes of temperature or pressure can eventually make any compressor fail.
Secondly, a compressor can contain a gross manufacturing defect. Oil does not return at a satisfactory rate when there is: a low, refrigerant velocity, short cycling, low load, traps or piping errors. Airside problems are known to be a significant cause of flooding. The compressor manufacturer determines maximum compression ratios.
Determining the compression ratio that a compressor is running at is easily done. See Info-Tec 32 for a full explanation. If a compressor is running with a compression ratio outside its design limits, the reason or reasons must be found and corrected or the compressor will burn out. The gauge readings taken will guide the service technician to a starting point. High head pressures with an air cooled condenser may be caused by a dirty or blocked condenser, fan problems, high ambient air temperatures, non-condensables in the system, misadjusted, or malfunctioning fan controls.
On water-cooled equipment, look for scaled-up condensers, high inlet water temperature, especially with cooling towers, and low water quantity. Usually, low suction pressure is the more common problem when too high a compression ratio is encountered. Low load, misadjusted, or improperly sized expansion device, mismatched or defective evaporator, poor suction pipe sizing and sloppy installation can all contribute to low suction pressure.
As mentioned in Info-Tec 32, the problem may be poor system design, making it necessary to operate the compressor outside its design conditions for the system to perform at all. If no other reason can be found for high compression ratio, recalculate the size of a system using all the known parameters to see if the present system should be able to handle the now accurately known load.
More refrigeration will need to be added. Perhaps the original design engineer was not notified of the entire load, or more load has been added to the original design. Overheated compressors suffer suction valve failure, worn pistons, sludge and carbon formation, and since proper lubrication is impossible, the compressor will eventually seize up.
Electrical failures are a major cause of compressor failure. Three-phase motor compressors can suffer from voltage and current imbalance. See Info-Tec 61, part II. Imbalance causes overheating. Single phasing, where one leg of the three phase is lost, is the ultimate imbalance.
Failure is rapid. There are many inexpensive devices that detect phase loss, imbalance, too high or too low a voltage, and quickly take the compressor off line before it can be badly damaged.
This may even involve the local electric utility. A three-phase compressor is a big, expensive item. Every protective device available ought to be used to prolong its useful life. Single-phase motor compressors may employ a complete set of starting components, or at least, a run capacitor. Should any of the components fail, the compressor will draw locked rotor current when trying to start.
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