Internal Pressure Relief Valves - Tecumseh AH5540E Service Handbook

Internal Pressure Relief Valves

Certain air conditioning compressors in the AJ, AW, AH, AV, AG, and SF families are quipped with a
unique internal pressure relief (IPR) valve. It prevents abnormally high head pressures from devel-
oping if a condenser fan motor fails or air passages in the condenser coil become blocked by dirt,
leaves, paper, etc. The IPR valve relieves pressure from the high pressure side to the low pressure
side of the system. It does not relieve pressure from the system to the atmosphere. See Table 6-2.
Compressors with IPR valves are frequently used in air conditioning and heat pump systems, and
occasionally used in refrigeration systems. The IPR valve may also open to relieve hydraulic pres-
sures in the event of slugging. This is apt to occur on startup if refrigerant has been allowed to mi-
grate to the compressor crankcase. It is a characteristic of the IPR valve that once it has "popped,"
it will not reset until the compressor has been stopped and the pressure allowed to equalize.
If a high to low side leak within the compressor is suspected, stop the system, equalize the pres-
sures, permit the IPR valve to close, and restart the compressor to double check before deciding
to change the compressor.
AG Models
AV Models
AW Models
AHA4520E
AHA4522E
AHA4524E
AHA4531E
AHA4540E
Table 6-2: Compressors with IPR valves
AHA7513Z
AHA7515J
AHA7521Z
AHA7524J
AJC5519E
AJD8520E
SFA5554E
SFA5558E
SFA5560E
SFA5572E
SFA5581E
SFAA530Z
SFAA536Z
SFAA540Z
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