Heat pumps · Error codes · Midea
P1Midea
P1 on a Midea heat pump: High pressure switch protection
Short answer
On a Midea heat pump, P1 means: High pressure switch 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: High pressure switch 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: High pressure protection.
Likely causes:
- Pressure sensor/switch not connected properly or has malfunctioned.
- Excess refrigerant.
- System contains air or nitrogen.
- High pressure side blockage.
- Poor condenser heat exchange.
- Main PCB damaged.
On the M-Thermal Mono R32 compact (MHC ...WD2N8-C, 5/7/9/12/14/16 kW)
The manual says: High pressure protection.
Likely causes:
- Heating/DHW: low water flow, high water temp, air in system, water pressure below 0.1 MPa, refrigerant overcharge, EXV stuck, undersized cylinder coil.
- Cooling: coil cover not removed, dirty/blocked coil.
On the M-Thermal Split R32 (MHA outdoor + HB hydronic box)
The manual says: High pressure switch protection.
Likely causes:
- Pressure sensor/switch not connected properly or has malfunctioned.
- Excess refrigerant.
- System contains air or nitrogen.
- High pressure side blockage.
- Poor condenser heat exchange.
- Outdoor unit main PCB damaged.
Is it safe?
On the M-Thermal Arctic HT R290 monobloc (MHC ...WD2N7)
| Does the heat pump stop? | Not stated |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| 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')
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| 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)
| Does the heat pump stop? | Not stated |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
On the M-Thermal Split R32 (MHA outdoor + HB hydronic box)
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| 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.
- Check the outdoor unit is not blocked by leaves, debris or snow and has clear space around it.
- Restart once via the controller (OFF then ON) as the manual allows; if the code returns, call an engineer.
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')
- Pressure sensor/switch not connected properly or has malfunctioned.
- Excess refrigerant.
- System contains air or nitrogen.
- High pressure side blockage.
- Poor condenser heat exchange.
- Main PCB damaged.
On the M-Thermal Mono R32 compact (MHC ...WD2N8-C, 5/7/9/12/14/16 kW)
- Heating/DHW: low water flow, high water temp, air in system, water pressure below 0.1 MPa, refrigerant overcharge, EXV stuck, undersized cylinder coil.
- Cooling: coil cover not removed, dirty/blocked coil.
On the M-Thermal Split R32 (MHA outdoor + HB hydronic box)
- Pressure sensor/switch not connected properly or has malfunctioned.
- Excess refrigerant.
- System contains air or nitrogen.
- High pressure side blockage.
- Poor condenser heat exchange.
- Outdoor unit main PCB 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 65 (table); 92 (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 77 (printed 74) · Reviewed 23 September 2026
- M-Thermal A Series Split R32 Service Manual (Midea CAC, 202004) ↗ · 202004 (file v31) · page 50 (table); 75 (troubleshooting) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026