Applicable Systems
Carrier ComfortLink Thermostat/Controller
Symptoms
Alarm E1 indicates a high discharge temperature condition. The controller shuts down the compressor to prevent damage. The display shows the current discharge temperature exceeding the setpoint of 150C (302F).
Possible Causes
- Condenser fan motor failure or reduced airflow across the condenser coil
- Refrigerant overcharge causing excessive head pressure
- Discharge temperature thermistor drifted out of calibration
- Contaminated or non-condensable gases in the refrigerant system
Troubleshooting Steps
- Step 1: Check condenser fan operation - verify all fans are running and rotating in the correct direction
Replace any failed fan motor or capacitor - Step 2: Inspect condenser coil for dirt, debris, or physical blockage
Clean the coil with approved coil cleaner and verify airflow restored - Step 3: Connect a manifold gauge set and compare actual discharge temperature with the thermistor reading
If thermistor reads incorrectly, replace with OEM part - Step 4: Recover refrigerant, evacuate system, and recharge to manufacturer specified weight
Verify subcooling and superheat are within specification after recharge
How to Reset
To reset E1: 1) Press and hold the Alarm Reset button for 3 seconds. 2) Verify discharge temperature has dropped below 130C (266F). 3) The controller will automatically restart the compressor if all interlocks are satisfied.
Common Replacement Parts
- K10-2440: Discharge temperature thermistor, Carrier Prelude (Verify resistance at 25C is approximately 10k ohm)
- HK25-0452: Condenser fan motor assembly (Verify capacitor value matches nameplate before installation)
Frequently Asked Questions
- Q: What causes E1 on Carrier Prelude units?
E1 is triggered when the discharge temperature exceeds 150C (302F), typically caused by condenser airflow problems, refrigerant charge issues, or a faulty thermistor.
- Q: Can I reset E1 without fixing the problem?
The alarm will clear temporarily but will reappear once the compressor starts and discharge temperature rises again. The root cause must be addressed.
Source: Carrier Transicold Prelude Service Manual, Form 62-12788
Category: Refrigeration