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11.7.1 OIL MANAGEMENT FOR RACK APPLICATION
Scroll refrigeration compressors may be used on multiple compressor parallel rack applications. This requires the
use of an oil management system to maintain proper oil level in each compressor. The sight glass connection
supplied can accommodate the mounting of the oil control devices.
11.8 SCROLL FUNCTIONAL CHECK
Refrigeration scroll compressors do not have internal suction valves. It is not necessary to perform
functional compressor tests to check how low the compressor will pull suction pressure. This type of test
may damage a scroll compressor. The following diagnostic procedure should be used to evaluate whether a
scroll compressor is functioning properly.
• Verify proper unit voltage.
• Normal motor winding continuity and short to ground checks will determine if the inherent overload
motor protector has opened or if an internal short to ground has developed. If the protector has opened,
the compressor must cool sufficiently to reset.
• With service gauges connected to suction and discharge pressure fittings, turn on the compressor. If
suction pressure falls below normal levels, the system is either low on charge or there is a flow blockage.
• Single-Phase Compressors - If the suction pressure does not drop and the discharge pressure does not
raise to normal levels the compressor is faulty.
• Three-Phase Compressors - If the suction pressure does not drop and the discharge pressure does not
rise, reverse any two of the compressor power leads and reapply power to make sure the compressor was
not wired to run in the reverse direction.
The compressor current draw must be compared to publish compressor performance curves at the
compressor operating conditions (pressures and voltages). Significant deviations (±20%) from published
values may indicate a faulty compressor.
11.9 STARTING SOUND LEVEL
During compressor start the sound level of compressor is slightly higher than during normal running
operation.
3-phase motor reverse wires connection is characterized by initial noise. To correct reverse rotation.
disconnect power and switch any two of the three power wires at the unit contractor. Never switch wires at
the compressor terminals
