Heat pumps · Error codes · Cool Energy
P4Cool Energy · EcoStore all-in-one exhaust-air DHW heat pump
P4 on a Cool Energy EcoStore all-in-one exhaust-air DHW heat pump: Compressor overloaded protection (current >10 A compressor only, or >IEH+10 with e-heater, checked 10 s after start)
Short answer
On a Cool Energy heat pump, P4 means: Compressor overloaded protection (current >10 A compressor only, or >IEH+10 with e-heater, checked 10 s after start). The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Compressor overloaded protection (current >10 A compressor only, or >IEH+10 with e-heater, checked 10 s after start).
Likely causes:
- Compressor broken.
- System blocked.
- Air/water or excess refrigerant.
- Water temperature sensor malfunction.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
What you can check
- Read and note the code shown on the controller display, then contact your installer or service engineer.
- Check the heat pump's breaker/isolator at the consumer unit is switched on (do not repeatedly reset if it trips).
What the engineer will check
- Check compressor windings and wiring/phase sequence.
- Check inverter drive parameters match compressor model.
- Check operating envelope (flow, pressures, load).
Who to ask for: refrigeration / F-gas heat pump engineer.
Certification: F-gas certification; electrical competence.
What you might notice
Sources
- Cool Energy EcoStore Heat Pump Water Heater - manual Rev1 ↗ · Rev1 · page 24-26 (printed) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026