294 on a Mitsubishi Heavy Industries Air-Conditioning Europe Hydrolution: Incompatible heat pump: The outdoor air heat pump is not compatible
Short answer
On a Mitsubishi Heavy Industries Air-Conditioning Europe heat pump, 294 means: Incompatible heat pump: The outdoor air heat pump is not compatible. 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: Incompatible heat pump: The outdoor air heat pump is not compatible.
Part involved: Incompatible heat pump.
When it shows: The outdoor air heat pump is not compatible.
Likely causes:
- Upgrade of outdoor unit failed; no software in outdoor unit.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| 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. 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': Upgrade of outdoor unit failed; no software in outdoor unit. Check sensor wiring/resistance, settings, flow (particle filter, pump) and supply as applicable.
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.82 (printed 80) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026