10500 on a Stiebel Eltron WPM heat pump manager / WPMsystem: An attempt to deactivate the charging pump to test the heat pump safety functions has failed. This may lead to a pressure drop in the heating circuit. It is possible to continue operating the system
Short answer
On a Stiebel Eltron heat pump, 10500 means: An attempt to deactivate the charging pump to test the heat pump safety functions has failed. This may lead to a pressure drop in the heating circuit. It is possible to continue operating the system. 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: An attempt to deactivate the charging pump to test the heat pump safety functions has failed. This may lead to a pressure drop in the heating circuit. It is possible to continue operating the system.
Part involved: compressor / expansion valve / pressure switches.
When it shows: An attempt to deactivate the charging pump to test the heat pump safety functions has failed. This may lead to a pressure drop in the heating circuit. It is possible to continue operating the system.
Likely causes:
- Check leads and the relevant plug-in connections.
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.
- Check the heating system pressure gauge reading is in the normal range stated by your installer.
- Check the outdoor unit air intake/discharge is not blocked by leaves, snow or ice (air source units).
What the engineer will check
- Check leads and the relevant plug-in connections.
Who to ask for: F-gas/refrigeration-qualified heat pump engineer (R290/A3 flammable-refrigerant competence for R290 models).
Certification: F-gas certification for fluorinated refrigerants (R410A/R454C); flammable refrigerant (R290) handling training for R290 models.
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