10503 on a Stiebel Eltron WPM heat pump manager / WPMsystem: The safety assembly of the heat pump has triggered a gas warning
Short answer
On a Stiebel Eltron heat pump, 10503 means: The safety assembly of the heat pump has triggered a gas warning. 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: The safety assembly of the heat pump has triggered a gas warning.
Part involved: ventilation module / fans / air sensors.
When it shows: The safety assembly of the heat pump has triggered a gas warning.
Likely causes:
- Possible ingress of refrigerant into the heating circuit. Do not bleed the radiators! Observe the procedure for venting heating systems; see operating and installation instructions for the heat pump. Poor system ventilation.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: yes - heat pump restarts after idle time (~10-12 min); locks out after 5 faults in 2 h run.
Manual reset: after 5 faults in 2 h: IWS/WPM reset.
What you can check
- Read and note the full message code and time from the WPM display (DIAGNOSIS / NOTIFICATIONLIST if accessible without a code).
- Check the heat pump and controller circuit breakers/isolators at the consumer unit are on.
What the engineer will check
- Possible ingress of refrigerant into the heating circuit. Do not bleed the radiators! Observe the procedure for venting heating systems; see operating and installation instructions for the heat pump. Poor system ventilation.
Who to ask for: MVHR/ventilation-competent heat pump engineer.
What you might notice
Sources
- WPM notification list (WPM V2.9) - multilingual; English section pp.15-26 (DOC-00081866) ↗ · WPM V2.9 · page 16 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026