A LOOK AT SERVICE SAFETY
Operation
119
VI.
Internal Pressure Relief
Valves
Certain air conditioning compressors in the AJ, AB,
AW, AH, AV, AG, and SF families are equipped
with a unique internal pressure relief (IPR) valve.
The IPR valve is used in air conditioning and heat
pump systems. It prevents abnormally high head
pressures from developing 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.
The IPR valve may also open to relieve hydraulic
pressures in the event of slugging. This is apt to
occur on startup if refrigerant has been allowed to
migrate 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 pressures,
permit the IPR valve to close, and restart the com-
pressor to double check before deciding to change
the compressor.
Table 6-2: Compressors Having IPR Valves
AG Models
AHA7521Z
SFA5560E
AHA4520E
AHA7524J
SFA5572E
AHA4522E
AJC5519E
SFA5581E
AHA4524E
AJD7520E
SFAA530Z
AHA4531E
AV Models
SFAA536Z
AHA4540E
AW Models
SFAA540Z
AHA7513Z
SFA5554E
AHA7515J
SFA5558E
