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. Phase voltage at or above 265V
2. Phase voltage at or below 172V
3. Unstable AC power supply
4. Low ambient temperature (T4<3°C) combined with low water-side temperature triggers freeze protection
5. Water side temperature dropping below critical thresholds due to low flow, low ambient temperature, or system stoppage
6. Abnormal state detected requiring compressor protection
7. Set temperature reached (normal stop)
8. Damage to cables
9. Excessive number of connections
10. Terminals not made to original specification
11. Damage to seals
12. Incorrect fitting of glands
13. Abnormal system state detected

Where to start

1. Measure AC phase voltage supply
2. Check voltage stability and duration of any excursion beyond limits
3. Monitor discharge temperature (Tp) and suction temperature (Th) during compressor operation