Midea Heat pump fault PP

What it means

Protection triggered when the temperature difference between outlet water (Twout) and inlet water (Twin) exceeds the threshold for a sustained period. In cooling mode: Twout-Twin>=3°C for 15 minutes. In heating/DHW mode: Twin-Twout>=3°C for 15 minutes.

Likely causes

1. Outlet pipe and inlet pipe connected reversely
2. Tw_in sensor and Tw_out sensor connected reversely on plate heat exchanger or Main control PCB
3. Tw_out/Tw_in temperature sensor failure
4. Connection cable of 4-way valve disconnected or misconnected
5. Main Control PCB fault (no voltage output to 4-way valve port)
6. 4-way valve failure
7. Low ambient temperature (T4<3°C) combined with low water-side temperature triggers freeze protection
8. Water side temperature dropping below critical thresholds due to low flow, low ambient temperature, or system stoppage
9. Power supply is abnormal
10. Power supply abnormality
11. Refrigerant leak from container or system

Where to start

1. Feel temperature of 4-way valve pipes by hand - C pipe should be hot, E pipe should be cold
2. Check if outlet pipe and inlet pipe are connected reversely; re-connect securely if so
3. Check if Tw_in and Tw_out sensors are connected reversely on plate heat exchanger or Main control PCB