30124 on a Stiebel Eltron WPM heat pump manager / WPMsystem: The minimum flow rate was undershot during defrosting
Short answer
On a Stiebel Eltron heat pump, 30124 means: The minimum flow rate was undershot during defrosting. 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 minimum flow rate was undershot during defrosting.
Part involved: water flow / pump / booster heater.
When it shows: The minimum flow rate was undershot during defrosting.
Likely causes:
- Water flow rate too low. If there is a filter in the heating circuit, check it.
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
- Water flow rate too low. If there is a filter in the heating circuit, check it.
Who to ask for: Heating / 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 22 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026