134 on a Hitachi Yutaki S80: Power supply phase anomaly - reverse/open phase (S80)
Short answer
On a Hitachi heat pump, 134 means: Power supply phase anomaly - reverse/open phase (S80). 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: Power supply phase anomaly - reverse/open phase (S80).
Part involved: S80 power phase.
Likely causes:
- Reverse or open phase.
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 134.
- 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.657 (viewer p.683); troubleshooting flowchart printed p.742 (viewer p.768) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026