Low Refrigerant Pressure
refrigeration
Description
Suction pressure has been less than -6.3 psig (-0.43 bar) for the configured time or 10 seconds, whichever is less; engine operation shuts down the engine and unit and alarms, and electric operation alarms only or shuts down refrigeration with PSCON still energized if configured.
Activation Conditions
Suction Pressure has been less than -6.3 psig (-0.43 bar) for the Low Suction Pressure Configuration time or 10 seconds (whichever is less).
Unit Behavior
Engine Operation: Engine and unit shutdown and alarm. Electric Operation: Alarm only or (if configured for shutdown) refrigeration system shutdown and alarm with PSCON still energized.
Reset Conditions
Auto Reset when suction pressure rises above 0.0 (bar or psig). Alarm may be manually reset via keypad or by turning the unit OFF, then ON again.
Corrective Actions
1. Visually Inspect Unit - Visually inspect unit for damage to liquid line causing restriction or signs of temperature drop at the filter drier. All tubing from the receiver to the evaporator section must be in good condition. Verify that there is no temperature drop at the drier or anywhere on the liquid line. 2. Perform Pretrip Check - Clear Active Alarm list, then run Pretrip and check for alarms. Any active alarms must be corrected and cleared before proceeding. 3. Check for Low Refrigerant Charge - Check refrigerant level in the receiver. Refer to Section 8.7.2. Generally, level should be between upper and lower sight glasses with a refrigerated compartment temperature of 35°F (1.0°C) or lower. 4. Manually Defrost Unit - Defrost unit and terminate automatically. Typical defrost cycle time is 5-20 minutes. Suction pressure should rise gradually during cycle. 5. Check Evaporator Section - Check evaporator section, return air bulkhead, air chute, and evaporator coil for cleanliness and airflow. Refer to Section 6.4.10 6. Check System Pressures - Install manifold gauge set and check and compare compressor discharge and suction pressures with those shown on the microprocessor. Suction pressure must be above 0.0 (psig or bar) Suction and Discharge Pressures must have the same reading on gauges and on microprocessor display. 7. Check Transducer Wiring. Refer to Section 8.9.11 a. Inspect transducer connector pins & terminals: CSP-1 to 1-3MSM-32, CSP-2 to 1-3MSM-9, and CSP-3 to 1-3MSM-21. Verify that there is no physical damage to sensor and the pins in plug are not damaged or corroded. b. Check for 5 VDC from 1-3MSM-9 to CSP-2 and for ground from CSP-1 to 1-3MSM-32. 8. Check Compressor Suction Modulation Valve (CSMV) - Refer to Section 8.9.7. 9. Check Expansion Valve (EVXV) - Refer to Section 8.9.8.