7–7 62-11637
00013 HIGH DISCHARGE PRESSURE
• ACTIVATION: Compressor discharge pressure switch (HPS) contacts are open. HPS contacts open when
the discharge pressure rises to 465 psig (32 bar).
• UNIT CONTROL: Shutdown and alarm.
• RESET CONDITION: Auto reset after 15 minutes if the compressor discharge pressure falls below 350
psig (24 bar), or alarm may be manually reset using the display mounted keys or by turning the unit off,
then back on again.
NOTE: Follow the steps below until a problem is found. Once a repair or correction has been made, the active
alarm should clear itself (refer to reset condition above). Operate the unit through the appropriate modes to see if
any active alarm occurs. Continue with the steps below as necessary.
CORRECTIVE ACTIONS:
1. If Alarm Occurs During Pretrip Test 12, 13 or 14
Check that SV1 is opening. During Pretrip tests 12, 13 and 14, SV1 may be de-energized for 1 second
to reduce discharge pressure. If SV1 fails to actually open during the 1 second that it is de-energized
this alarm may occur. Repair SV1 as required.
2. Check System Pressures
Install manifold gauge set and check and compare compressor discharge & suction pressures with
those shown in Unit Data. Refer to Section 8.9.12 for instruction on comparison. If discharge pressure
is in normal range, proceed to step 5.
3. Check Airflow Through Radiator & Condenser Coil
a. Inspect condenser & radiator. Ninety percent or more of the coil surface must be undamaged. Con-
denser/Radiator coil must be clean.
b. Check airflow (with unit running). Verify even airflow through the entire coil, and no “dead” spots.
c. Check upper and lower fan belt tension & condition. Verify no glazing, cracking, or slipping. Replace
if required. Refer to Section 8.6.
4. Check Refrigerant Charge
Refer to Section 8.7.2. Charge must be correct.
5. Check HPS Power And Wiring
a. Inspect switch, connector pins & terminals. Verify that there is no physical damage to the switch.
Check the connections for damage and corrosion.
b. Disconnect switch connector and check for power at the A position (includes J1, SROS, and SP-9).
If a minimum of 11 VDC is not present, check connectors and wiring between terminals for damage,
moisture or corrosion.
c. Check continuity from the switch connector B position to PCM-15 (includes SP-5). If good continuity
is not present, check connectors and wiring between terminals for damage, moisture or corrosion.
6. Check HPS Switch
a. With discharge pressure below the switch closing pressure (refer to Section 2.9). Disconnect switch
connector and check continuity across the switch. Switch closed.
b. Check switch operation. Test switch. Refer to Section 8.9.11 step b.
7. Perform Pretrip
Run Pretrip and check for alarms. Any active alarms must be corrected and cleared before proceed-
ing.
8. Refer to Refrigeration Troubleshooting
Refer to Section 9.3. Discharge must be in range for the current ambient and refrigerated compart-
ment conditions.
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