228 on a Mitsubishi Heavy Industries Air-Conditioning Europe Hydrolution: Failed defrosting: Failed 10 consecutive defrostings
Short answer
On a Mitsubishi Heavy Industries Air-Conditioning Europe heat pump, 228 means: Failed defrosting: Failed 10 consecutive defrostings. 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: Failed defrosting: Failed 10 consecutive defrostings.
Part involved: Failed defrosting.
When it shows: Failed 10 consecutive defrostings.
Likely causes:
- System temperature too low and/or poor flow; insufficient available system volume; significant wind effect; clogged particle filter.
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. 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': System temperature too low and/or poor flow; insufficient available system volume; significant wind effect; clogged particle filter. 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.81 (printed 79) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026