Midea Heat pump fault H9

What it means

Tw2 Zone 2 water flow temperature sensor error. Occurs when Double zone is on (User Interface- For Serviceman - Temp. type setting - Double zone=1), while Main Control PCB cannot detect the right Tw2 sensor value.

Likely causes

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

Where to start

1. Inspect flow switch for leaks
2. Check start sequence of internal vs external pumps
3. Monitor Min(Twout,Twin,T1) against 15°C threshold for heat pump stop condition