100 on a Hitachi heat pump: Compressor protection (shown as EE on outdoor unit) - alarms 02, 07, 08, 45, 47 three times within 6 hours
Short answer
On a Hitachi heat pump, 100 means: Compressor protection (shown as EE on outdoor unit) - alarms 02, 07, 08, 45, 47 three times within 6 hours. 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: Compressor protection (shown as EE on outdoor unit) - alarms 02, 07, 08, 45, 47 three times within 6 hours.
Part involved: compressor protection.
Likely causes:
- Repeated refrigerant-circuit protection trips.
Is it safe?
Switch the heat pump off at its isolator and call an engineer.
| 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: After cause 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 100.
- Review alarm history for the underlying 02/07/08/45/47 alarms and resolve that cause.
- Check compressor windings/insulation and refrigerant circuit.
Who to ask for: F-gas certified refrigeration / heat pump engineer.
Certification: F-gas certificate (Category I); A2L training for R32 units.
What you might notice
Sources
- Installation & Operation Manual - YUTAKI series and YUTAKI Cascade Controller (R410A series / R32 series) ↗ · PMML0510 rev.1 - 10/2019 · page p.147 (PDF p.158) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026