H7 on a Midea heat pump: Power overvoltage and under-voltage protection
Short answer
On a Midea heat pump, H7 means: Power overvoltage and under-voltage protection. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 4 sources
What it means
On the M-Thermal Arctic HT R290 monobloc (MHC ...WD2N7)
The manual says: Power overvoltage and under-voltage protection.
Likely causes:
- See R290 service manual troubleshooting (section 6) for this code.
On the M-Thermal Mono R32 (MHC ...W/D2N8-B / -B2 'Arctic')
The manual says: Abnormal main circuit voltage.
Likely causes:
- Power supply voltage not within ±10% of rated voltage or a phase is missing.
- Outdoor unit powered on immediately after being powered off.
- Loosened wiring within electric control box.
- High voltage circuit error.
- Main PCB damaged.
On the M-Thermal Mono R32 compact (MHC ...WD2N8-C, 5/7/9/12/14/16 kW)
The manual says: Main circuit voltage failure.
Likely causes:
- Supply voltage outside range.
- rapid repeated power cycling.
- main control board circuit defect.
On the M-Thermal Split R32 (MHA outdoor + HB hydronic box)
The manual says: Abnormal main circuit voltage.
Likely causes:
- Power supply voltage not within 90%~110% of rated voltage.
- Outdoor unit main PCB is damaged.
Is it safe?
On the M-Thermal Arctic HT R290 monobloc (MHC ...WD2N7)
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
On the M-Thermal Mono R32 (MHC ...W/D2N8-B / -B2 'Arctic')
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
On the M-Thermal Mono R32 compact (MHC ...WD2N8-C, 5/7/9/12/14/16 kW)
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
On the M-Thermal Split R32 (MHA outdoor + HB hydronic box)
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
What you can check
- Read and note the exact code shown on the controller display.
- Check the heat pump's breaker/isolator at the consumer unit is on.
- If the breaker has tripped or trips again, leave the unit off and call an engineer; do not keep resetting it.
What the engineer will check
On the M-Thermal Arctic HT R290 monobloc (MHC ...WD2N7)
- See R290 service manual troubleshooting (section 6) for this code.
On the M-Thermal Mono R32 (MHC ...W/D2N8-B / -B2 'Arctic')
- Power supply voltage not within ±10% of rated voltage or a phase is missing.
- Outdoor unit powered on immediately after being powered off.
- Loosened wiring within electric control box.
- High voltage circuit error.
- Main PCB damaged.
On the M-Thermal Mono R32 compact (MHC ...WD2N8-C, 5/7/9/12/14/16 kW)
- Supply voltage outside range.
- rapid repeated power cycling.
- main control board circuit defect.
On the M-Thermal Split R32 (MHA outdoor + HB hydronic box)
- Power supply voltage not within 90%~110% of rated voltage.
- Outdoor unit main PCB is damaged.
Sources
- R290 M thermal Arctic HT Series Service Manual ↗ · 2025-10-15 v5 (from file name) · page 92 · Reviewed 23 September 2026
- Midea M thermal Arctic Mono (4~16kW) Service Manual ↗ · not stated (MBT Confidential) · page 64 (table); 87 (troubleshooting) · Reviewed 23 September 2026
- M-thermal Mono ATW Heat Pump Installation and Owner's Manual (5/7/9/12/14/16 kW) ↗ · 16125300001699 V4.0 · page PDF 76 (printed 73) · Reviewed 23 September 2026
- M-Thermal A Series Split R32 Service Manual (Midea CAC, 202004) ↗ · 202004 (file v31) · page 50 (table); 71 (troubleshooting) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026