220 on a Mitsubishi Heavy Industries Air-Conditioning Europe Hydrolution: High pressure alarm: The high pressure switch (63H1) has deployed 5 times within 60 minutes or has been deployed for 60 minutes continuously
Short answer
On a Mitsubishi Heavy Industries Air-Conditioning Europe heat pump, 220 means: High pressure alarm: The high pressure switch (63H1) has deployed 5 times within 60 minutes or has been deployed for 60 minutes continuously. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: High pressure alarm: The high pressure switch (63H1) has deployed 5 times within 60 minutes or has been deployed for 60 minutes continuously.
Part involved: High pressure alarm.
When it shows: The high pressure switch (63H1) has deployed 5 times within 60 minutes or has been deployed for 60 minutes continuously.
Likely causes:
- Insufficient air circulation or blocked heat exchanger; open/short circuit on input for 63H1; defective high pressure switch; expansion valve not connected correctly; service valve closed; defective control board in outdoor unit; low or no flow during heating; defective circulation pump; defective fuse FA.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: yes (select 'reset alarm' in the alarm menu).
What you can check
- Note the alarm number/text shown on the display. Check the consumer-unit breakers/isolators for the indoor and outdoor units are on. Check the outdoor unit is not blocked by leaves, snow or ice and its drain is clear (look only - do not open the casing). Check radiator/underfloor thermostats in the house are not all closed (user manual). Check the heating system pressure gauge reads in the normal range (about 0.5-1.5 bar when cold for Hydrolution per user manual). On the RC-HY controller you may select 'reset alarm' once (installation manual: 'in most cases it is enough'); if the red lamp stays or the alarm returns, select 'aid mode' (if enabled) or 'add. heat only' in menu 4.2 and contact the installer.
What the engineer will check
- Per manual 'May be due to': Insufficient air circulation or blocked heat exchanger; open/short circuit on input for 63H1; defective high pressure switch; expansion valve not connected correctly; service valve closed; defective control board in outdoor unit; low or no flow during heating; defective circulation pump; defective fuse FA. Refrigerant/outdoor-unit work (service valves, charge, sensors Tho-R/A/D/S, LPT, 63H1, fan motor, inverter/control PCBs) must be done by an F-gas certified engineer.
Who to ask for: Heat pump / refrigeration engineer (manufacturer-trained).
Certification: F-gas certification for refrigerant-circuit work; electrical competence (Part P/18th Edition) for PCB/wiring.
What you might notice
Sources
- Installation Manual - Air to Water Heat Pump using R32 refrigerant, Hydrolution (HM) ↗ · PSC012D169 (202201) · page PDF p.80 (printed 78) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026