P05 on a Toshiba heat pump: Power supply voltage failure
Short answer
On a Toshiba heat pump, P05 means: Power supply voltage failure. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 4 sources
What it means
On the R32 Estia 1-Series (split, Wall-Mounted and All-in-One)
The manual says: Power supply voltage failure.
Part involved: mains supply, inverter board.
When it shows: Supply voltage extremely high or low.
Likely causes:
- Supply voltage (1ph 220-240V / 3ph 380-415V +-10%).
On the Estia (Series 4) Standard & Powerful
The manual says: Power supply voltage error.
Part involved: mains supply, inverter board.
When it shows: Supply voltage extremely high or low.
Likely causes:
- Supply voltage (AC230 V +-23 V).
On the Estia 5 Series (Standard)
The manual says: Power supply voltage error.
Part involved: mains supply, inverter board.
When it shows: Supply voltage extremely high or low.
Likely causes:
- Supply voltage.
On the Estia 5 Series Powerful (Hi Power / Extreme)
The manual says: Power supply voltage error.
Part involved: mains supply, inverter board.
When it shows: Trigger thresholds not printed in the IM; see SM.
Likely causes:
- Supply voltage.
Is it safe?
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: no.
Manual reset: Cause must be fixed by an engineer; hardware faults reappear until repaired.
What you can check
- Note the check code shown on the remote controller and the outdoor/hydro model numbers before contacting an engineer.
- Check the consumer-unit breakers/isolators for the outdoor unit, hydro unit and backup heater are switched on.
What the engineer will check
On the R32 Estia 1-Series (split, Wall-Mounted and All-in-One)
- Follow manufacturer's check-code flowchart.
- Supply voltage (1ph 220-240V / 3ph 380-415V +-10%).
Who to ask for: Heat pump engineer with electrical competence.
Certification: Electrical competence (Part P / 18th Edition).
On the Estia (Series 4) Standard & Powerful
- Follow manufacturer's check-code flowchart.
- Supply voltage (AC230 V +-23 V).
Who to ask for: Heat pump engineer with electrical competence.
Certification: Electrical competence (Part P / 18th Edition).
On the Estia 5 Series (Standard)
- Follow manufacturer's check-code flowchart.
- Supply voltage.
Who to ask for: Heat pump engineer with electrical competence.
Certification: Electrical competence (Part P / 18th Edition).
On the Estia 5 Series Powerful (Hi Power / Extreme)
- Follow manufacturer's check-code flowchart.
- Supply voltage.
Who to ask for: Heat pump engineer with electrical competence.
Certification: Electrical competence (Part P / 18th Edition).
What you might notice
Sources
- Air to Water Heat Pump Service Manual - Wall Mounted Type (File No. AE0-2101W) ↗ · AE0-2101W · page p.117 (printed page; PDF page +1) · Reviewed 23 September 2026
- Quick Reference Air to Water Heat Pump Series 4 Standard & Powerful Types ↗ · Quick Reference Series 4 Standard & Powerful (undated) · page p.63 (printed page; PDF page +1) · Reviewed 23 September 2026
- Air to Water Heat Pump Service Manual (File No. A10-1704) - Estia 5 Series Indoor/Outdoor ↗ · A10-1704 · page p.91 (printed page; PDF page +1) · Reviewed 23 September 2026
- Hydro Unit Installation Manual EF99812301-4 (Powerful) ↗ · EF99812301-4 · page p.60 (printed page; PDF page +1) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026