Trane TVR Pro CO Series Service Manual page 105

2.21 P4, H6: Discharge temperature protection
Digital display output
Description
 Discharge temperature protection.
 All units stop running.
 Error code is only displayed on the unit with the error.
Trigger / recover condition
 Trigger condition:
For P4 protection: Discharge temperature (T7C1/2) ≥ 120
For H6 protection: P4 protection appears three times in 100 minutes.
 Recover condition: Discharge temperature (T7C1/2) ≤ 90
 Reset method:
For P4 protection: Resume automatically.
For H6 protection: Manually restart.
Possible causes
 Outdoor unit stop valves are closed.
 Temperature sensor/switch not connected
properly or has malfunctioned.
Procedure
ODU stop valves are closed
Compressor top temperature sensor,
discharge pipe temperature sensor
and/or discharge temperature switch
connections on main PCB are loose
Compressor top temperature sensor
and/or discharge pipe temperature
sensor have short circuited or failed
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P4 / H6
No
1
No
2
No
C.
o
o C.
 Insufficient refrigerant.
 System blockage.
 Indoor load too large.
Yes
Open the stop valves
Ensure the sensors and switch are
Yes
Yes
Replace the faulty sensor(s)
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104
 System contains air or nitrogen.
 Poor condenser heat exchange.
 Main PCB damaged.
connected properly