Midea M-Thermal Arctic HT R290 Mono fault H7

What it means

Protects the M-Thermal Split from abnormally high or abnormally low AC supply voltages. Triggered when phase voltage is at or above 265V, or at or below 172V.

Likely causes

1. Input voltage too high (≥265V)
2. Input voltage too low (≤170V)
3. Transient power off/on event (temporary, self-clearing)
4. Inverter PCB failure
5. Phase voltage at or above 265V
6. Phase voltage at or below 172V
7. Unstable AC power supply
8. Low ambient temperature (T4<3°C) combined with low water-side temperature triggers freeze protection
9. Water side temperature dropping below critical thresholds due to low flow, low ambient temperature, or system stoppage
10. Abnormal state detected requiring compressor protection
11. Set temperature reached (normal stop)
12. Abnormal system state detected

Where to start

1. Check if H7 occurs when power off, or occurs when power turned on immediately after power off and lasts 5 minutes then disappears automatically - if yes, this is normal system protection and no action is needed
2. If not a transient condition, measure the input voltage on terminal blocks - check if it is too high (≥265V) or too low (≤170V)
3. If input voltage is out of range, adjust the input power supply