Bryant R-22 Compressor Failures, Mechanical Failures, Copeland Scroll Compressor, Scroll Gas Flow

COPELAND SCROLL COMPRESSOR

Scroll Gas Flow

Compression in the scroll is
created by the interaction of
an orbiting spiral and a
stationary spiral. Gas enters
an outer opening as one of the
spirals orbits.	1

2	3
The open passage is sealed off	As the spiral continues to orbit,
as gas is drawn into the spiral.	the gas is compressed into an
	increasingly smaller pocket.

4	5
By the time the gas arrives at	Actually, during operation, all
the center port, discharge	six gas passages are in various
pressure has been reached.	stages of compression at all
	times, resulting in nearly con-
	tinuous suction and discharge.

A90198

Fig. 11 – Scroll Compressor Refrigerant Flow

The compressors used in these products are specifically designed to operate with designated refrigerant and cannot be interchanged. The compressor is an electrical (as well as mechanical) device. Exercise extreme caution when working near compressors. Power should be shut off, if possible, for most troubleshooting techniques. Refrigerants present additional safety hazards.

!CAUTION

PERSONAL INJURY HAZARD

Failure to follow this caution may result in personal injury.

Wear safety glasses, protective clothing, and gloves when handling refrigerant.

The scroll compressor pumps refrigerant through the system by the interaction of a stationary and an orbiting scroll. (See Fig. 11.) The scroll compressor has no dynamic suction or discharge valves, and it is more tolerant of stresses caused by debris, liquid slugging, and flooded starts. The compressor is equipped with an internal pressure relief port. The pressure relief port is a safety device, designed to protect against extreme high pressure. The relief port has an operating range between 550 to 625 psi differential pressure for Puronr and 350 to 450 psi differential pressure for R-22. Scrolls have a variety of shut down solutions, depending on model, to prevent backward rotation and eliminate the need for cycle protection.

Compressor Failures

Compressor failures are classified in 2 broad failure categories; mechanical and electrical. Both types are discussed below.

Mechanical Failures

A compressor is a mechanical pump driven by an electric motor contained in a welded or hermetic shell. In a mechanical failure, motor or electrical circuit appears normal, but compressor does not function normally.

!WARNING

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal injury or death.

Do not supply power to unit with compressor terminal box cover removed.

!WARNING

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal injury or death.

Exercise extreme caution when reading compressor currents when high-voltage power is on. Correct any of the problems described below before installing and running a replacement compressor.

Locked Rotor

In this type of failure, compressor motor and all starting components are normal. When compressor attempts to start, it draws locked rotor current and cycles off on internal protection. Locked rotor current is measured by applying a clamp-on ammeter around common (blk) lead of compressor. Current drawn when it attempts to start is then measured. Locked rotor amp (LRA) value is stamped on compressor nameplate.

If compressor draws locked rotor amps and all other external sources of problems have been eliminated, compressor must be replaced. Because compressor is a sealed unit, it is impossible to determine exact mechanical failure. However, complete system should be checked for abnormalities such as incorrect refrigerant charge, restrictions, insufficient airflow across indoor or outdoor coil, etc., which could be contributing to the failure.

Runs, Does Not Pump

In this type of failure, compressor motor runs and turns compressor, but compressor does not pump refrigerant. A clamp-on ampmeter on common leg shows a very low current draw, much lower than rated load amp (RLA) value stamped on compressor nameplate. Because no refrigerant is being pumped, there is no return gas to cool compressor motor. It eventually overheats and shuts off on its internal protection.

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