5 on a Hitachi heat pump: Reception of abnormal operation code for detection of power source phase
Short answer
On a Hitachi heat pump, 5 means: Reception of abnormal operation code for detection of power source phase. 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: Reception of abnormal operation code for detection of power source phase.
Part involved: power source phase detection.
Likely causes:
- Power source with abnormal wave pattern; main power supply phase reversed or one phase not connected.
Is it safe?
Switch the heat pump off at its isolator and call an engineer.
| 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: Stop the unit (via unit controller / power off-on) after the cause is fixed.
What you can check
- Read and note the alarm code and any retry code (e.g. P70) shown on the unit controller.
- Check the heat pump supply breaker/isolator at the consumer unit is ON.
- Restart once via the unit controller (or switch off/on at the isolator) - the manual states the unit must be stopped to release most alarms; if the code returns, call an engineer.
What the engineer will check
- Follow SMGB0146 section 6.7 troubleshooting flowchart for alarm 5.
- Measure supply voltage and phase sequence/imbalance at the terminal board.
- Check supply cable size and connections per manual.
Who to ask for: Electrician / heat pump service engineer.
Certification: BS 7671 competent electrician for supply issues.
What you might notice
Sources
- Service Manual - YUTAKI R32 / R410A series (Split, Monobloc and Hydrosplit systems) ↗ · SMGB0146 rev.0 - 12/2022 · page table printed p.652 (viewer p.678); troubleshooting flowchart printed p.669 (viewer p.695) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026