Archive for March, 2019

Compressor Electrical Problems

Grounded, Open, or Shorted Motor Hermetic motors are rugged and reliable but they can fail in several ways. A broken wire in a motor winding can prevent the motor from running. It can also fail due to an internal short circuit where one or more motor winding conductors short together or short to ground. Any […]

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Other System Problems that can Result in Compressor Failures

In addition to the failure modes previously described, there are several other system-related problems that, if not corrected, can result in the mechanical failure of a compressor. The major ones are listed here for consideration when troubleshooting compressors. Detailed coverage about the cause and effect of each of these system problems is beyond the scope […]

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Causes of Compressor Failures – Leaks

If a leak exists at the electrical terminals of a hermetic compressor (Figure SP-9-5), it cannot be repaired and the compressor must be replaced. If a leak exists at the girth weld or at the stubs, recover all refrigerant and repair the leak with silver brazing alloy. If the leak cannot be repaired, replace the […]

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Causes of Compressor Failures – Low or No Capacity (Runs But Does Not Pump)

Compressors depend upon their valves and rings to provide a seal between the high-pressure and low-pressure sides of the system and the compressor. If either is damaged, correct operating pressures can never be developed. This condition can be checked using the gauge manifold set. If the system is properly charged, but the suction pressure is […]

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Compressor Types

The most common types o f compressors encountered when servicing residential and light commercial equipment are the reciprocating, rotary, and scroll-type hermetic compressors. In a hermetic compressor (Figure SP-9-1) the motor is connected directly to the compressor crankshaft. Both components are sealed in a welded steel enclosure or shell. Because it is sealed, the entire […]

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COMPRESSOR CHECKS AND ELECTRICAL MEASUREMENTS

Purpose – The compressor is the heart of the cooling system. It creates the pressure difference that causes the refrigerant flow around the system. Compressor motors are one of the primary electrical loads used in cooling systems. Compressor checks and measurements are made mainly when troubleshooting the unit. Since compressors are expensive and their replacement […]

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Switches and Contactor/Relay Switched Contacts Troubleshooting

Once a switch or set of contactor/relay switched contacts (F ig u re SP-8-4) have been identified as the probable cause of an electrical problem by using hopscotch troubleshooting, the contacts should be tested to confirm their position (open or closed). Switches and contactor/relay switched contacts can be tested with continuity measurements. A continuity measurement […]

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