High Discharge Pressure
refrigeration
Description
The compressor discharge pressure is over 200 psi with the switch open for 3 seconds, and the unit alarms; if the compressor is on, it also shuts down the compressor.
Activation Conditions
Compressor discharge pressure switch is open and discharge pressure is >200 psi. Pressure must be High for three seconds consecutively.
Unit Behavior
Compressor only: If activated while compressor is off, Alarm Condition only. If activated while compressor is on shutdown, compressor and alarm.
Reset Conditions
Compressor high discharge pressure switch closed and Power Switch is ON OR Alarm Reset OR Cycle Power
Corrective Actions
1. Check System Pressures - Install manifold gauge set, and check and compare compressor discharge and suction pressures with those shown in Unit Data. Refer to Section 8.9.11 for instruction on comparison. If discharge pressure is in normal range, proceed to step 3. 2. Check Airflow through Condenser Coil a. Inspect condenser. Ninety percent or more of the coil surface must be undamaged. Condenser coil must be clean. b. Check airflow (with unit running). Verify even airflow through the entire coil and no “dead” spots. c. Check condenser fan rotation/operation. Fan should operate correctly. Air should be directed in through cab side of condenser and out through the condenser fan. 3. Check Refrigerant Charge - Refer to Section 8.7.2. Charge must be correct. 4. Check HPS Power and Wiring a. Inspect switch, connector pins and terminals. Verify that there is no physical damage to the switch. Check the connections for damage and corrosion. b. Check continuity from the CCM J1-6 to HPS-B and J1-12 to HPS-A. If they are OK replace HPS. If good continuity is not present, check connectors and wiring between terminals for damage, moisture, or corrosion. 5. Check HPS a. With discharge pressure above minimum and below maximum switch opening pressure (refer to Section 2.10). Check continuity between the A and B position of the switch connector. Switch should be closed. b. Check switch operation. Test switch. 6. Refer to A/C Troubleshooting - Discharge must be in range for the current ambient and cab conditions.