P6 on a Baxi heat pump: Module protection
Short answer
On a Baxi heat pump, P6 means: Module protection. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 2 sources
What it means
On the Assure Monobloc ASHP (Assure Mono 5/7/9/12/16)
The manual says: Module protection.
Part involved: inverter module, compressor, PFC.
Likely causes:
- Supply voltage low; units too close; heat exchanger dirty/blocked; fan not running; refrigerant overcharged; low water flow/air/insufficient pump head; outlet sensor loose; DHW coil too small; module wires/screws loose or thermal paste dried; wire connection loose; drive board defective; compressor defective.
On the HP40 / Baxi Assure HP50 Monobloc ASHP
The manual says: Inverter module protection (L0-L9 sub-codes).
Part involved: inverter module, compressor, PFC.
Likely causes:
- Check heat pump system pressure; compressor phase resistance; U/V/W connection sequence inverter board-compressor; L1/L2/L3 connection inverter board-filter board; inverter board.
Is it safe?
On the Assure Monobloc ASHP (Assure Mono 5/7/9/12/16)
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: unknown.
Manual reset: Power OFF/ON after correcting cause (ISM 13.4).
On the HP40 / Baxi Assure HP50 Monobloc ASHP
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: unknown.
Manual reset: Installer: correct cause then power OFF/ON (ISM 13.4).
What you can check
- Note the exact code shown on the controller and when it appeared.
- Check the outdoor unit is not blocked by leaves, debris, snow or covers and has clear airflow.
- Check the heat pump's consumer-unit breaker / isolator is on (do not open any panels).
- If the code persists or returns, contact a heat pump engineer.
What the engineer will check
On the Assure Monobloc ASHP (Assure Mono 5/7/9/12/16)
- Supply voltage low; units too close; heat exchanger dirty/blocked; fan not running; refrigerant overcharged; low water flow/air/insufficient pump head; outlet sensor loose; DHW coil too small; module wires/screws loose or thermal paste dried; wire connection loose; drive board defective; compressor defective.
Who to ask for: heat pump engineer with electrical competence.
Certification: Qualified electrician / manufacturer-trained heat pump engineer; F-gas if refrigerant circuit is opened.
On the HP40 / Baxi Assure HP50 Monobloc ASHP
- Check heat pump system pressure; compressor phase resistance; U/V/W connection sequence inverter board-compressor; L1/L2/L3 connection inverter board-filter board; inverter board.
Who to ask for: heat pump engineer with electrical competence.
Certification: Qualified electrician / manufacturer-trained heat pump engineer; F-gas if refrigerant circuit is opened.
What you might notice
Sources
- Installation and owner's manual - Heat Pump air/water 'inverter' Assure Mono 5, 7, 9, 12, 16 ↗ · Back cover shows '7762758 - v05 - 19082020' (same number as the Assure Split manual - probably shared back-cover artwork) · page 75 · Reviewed 23 September 2026
- Installation and Service Manual - Heat Pump air/water 'inverter' HP40/50-4-1PHMB to HP40/50-13-3PHMB (United Kingdom) ↗ · 784570-01 (v1) · page 77 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026