SRL Service Manual
Revision 00
July 2007
Page 40 of 56
10.2.2 Low (Evaporator) Pressure (Alarm)
What it means: Low pressure switch registers a refrigerant pressure below 22 psig (1.5 barg) for 2
minutes or more.
What it does: Cuts power to compressor compressor contactor & alarm contacts. Turns dryer
OFF. Turns on Warning Light & blinks “LP” on the digital display.
Possible Causes & Remedies:
1) A low refrigerant charge is causing the compressor to pull the suction pressure
below 22 psig.
Remedy – Check or leaks at welds, threaded connections, schrader valve caps,
and joints of the condenser and evaporator. Repair the leak, pull the system to deep
vacuum and charge the dryer with the correct amount of refrigerant as specified in
the Section 2.3.
2) A defective low pressure switch is giving a wrong signal to the controller. Can be
confirmed by checking the evaporator pressure with a gauge.
Remedy - Replace the detective component.
To Reset: Press ALARM RESET. Power restored to alarm relay, Warning Light goes off.
Dryer remains OFF. Display clears.
Press ON/OFF to restart dryer.
Notes: Alarm can only be cleared if the pressure is above 36 psig (2.5 barg).
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