Operational Testing.

TM5-4110-234-14

TO 40R7-5-7-1

(b) If valves are leaking or a gasket is blown, the pressure will equalize rapidly. Maximum allowable

discharge pressure drop is 3 psi per minute after initial drop of 10-15 psi in first half minute. The compressor bank with a

blown gasket can also usually be detected by touch, since the head temperature will normally be much hotter than a bank

with good gaskets.

assembly and inspect suction valves.

(2) Excessive or unusual noise.

(a) Check oil level.

(b) Check mounting.

d. Motor burnout. (F1OOOOR-6 only.) When a compressor motor burns out it is necessary to replace the

complete motor compressor assembly and clean the refrigeration system of all contaminants. Burnout of a compressor

motor is indicated by lack of continuity of the motor windings and the condition of compressor oil. Cause of compressor

motor burnout include the following:

(1) Low line voltage, which causes motor windings to overheat. Before burning out completely, the overheated

windings cause chemical breakdown of the refrigerant and the oil to form sludge and other system contaminants.

(2) Loss of refrigerant. An inadequate charge of refrigerant. gas in the system reduces the amount of cooling

gas within the compressor, resulting in gradual overheating of the motor and failure of the winding.

(3) High head pressure. High head pressures can be caused by clogged or dirty condenser coils or screens, or

by an inoperative condenser fan. High head pressure requires the compressor to work harder, creating additional heat

which ultimately can result in motor burnout. Poor ventilation around the condenser, and extremely high ambient

temperatures can also cause motor failures.

(4) Moisture in system. Leakage of air into the refrigeration system starts a chain reaction which can result in

motor burnout. Air contains oxygen and moisture which combined with refrigerant gas form hydrochloric and hydrofluoric

acids. These combined with compressor oil form an acid sludge which is carried throughout the system, and which

attacks the motor windings, causing short circuits and burnout.

(5) It is important to diagnose the type of compressor motor failure for two reasons. Simple failure, without motor

burnout, does not require the extensive cleaning of the entire refrigeration system that burnout requires. Also, motor

burnout indicates other problems that have contributed to the failure, and these problems must be corrected or avoided to

prevent repetition of the burnout. Drain a small quantity of oil into a clear glass container. If the oil is clean and clear, and

does not have an acrid smell, the compressor did not fail because of motor burnout. If the oil is black, contains sludge and

has an acrid odor, the compressor failed because of motor burnout, and the refrigeration system must be cleaned to

prevent residual contaminants from causing repeated burnouts when the compressor is replaced.

e. Clean-up procedure after a burnout. (F10000RG-6 only.)

(1) Close compressor suction and discharge service valves and bleed refrigerant from compressor. Save

remaining refrigerant in system.

(2) Remove suction and discharge shut-off valve bolts and all other connections to damaged compressor.

Remove damaged compressor and replace with a new compressor. On severe motor burnouts, discharge the system and

clean all valves and components before connecting the replacement compressor.

(3) Install new liquid line filter-drier.

(4) Evacuate and dehydrate replacement compressor and check to see that oil in compressor is at proper level.

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