Midea M-Thermal Arctic HT R290 Mono fault P5

What it means

P5 triggers when the temperature difference between outlet water temperature (Twout) and inlet water temperature (Twin) exceeds specified thresholds. Triggering conditions: Twout-Twin≥30°C in heating/DHW mode; Twout-Twin≥17°C in cooling mode.

Likely causes

1. E8/E0 error occurring at roughly the same time (water flow related issue)
2. Water flow smaller than normal due to blocked pipe or filter, or incorrect water pressure/flow rate
3. Flow switch leak due to faulty sealing ring
4. External pump starts before internal pump (PUMPI) starts
5. The water flow in the pipe is not consistent with arrow on the flow switch
6. Flow switch FS plug (CN8) is not connected properly
7. Water flow switch rake mechanically damaged
8. Flow switch not installed properly
9. Water flow switch mechanically damaged (rake does not trigger contact closure)
10. Pump stalling due to impeller obstruction
11. Water pump internal failure despite correct wiring
12. Water pump malfunction indicated by abnormal indicator light status
13. Water pump leak due to faulty sealing ring
14. Water pump connection is correct, the water pump icon on the User Interface is lit, while no indicator lights on water pump is lit
15. Pump idling
16. Pump idling due to insufficient water/air in circuit

Where to start

1. Check 'Unit Status-Operation Parameter-water flow' value against normal range
2. Pull out Tw_out/Tw_in sensor from plate heat exchanger, leave in air for 10 mins, compare sensor and air temperature
3. Check whether heat pump runs in DHW mode and heat exchanger coil size