MIN-SOURCE on a Stiebel Eltron WPM 3 heat pump manager: The defined minimum source temperature was not reached
Short answer
On a Stiebel Eltron heat pump, MIN-SOURCE means: The defined minimum source temperature was not reached. 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 defined minimum source temperature was not reached.
Part involved: brine circuit.
When it shows: The defined minimum source temperature was not reached.
Likely causes:
- Check the minimum source temperature and change it if required; check source flow rate and source sizing.
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 - restarts after IWS fault time/idle time.
Manual reset: after 5 faults in 2 h run: IWS 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.
What the engineer will check
- Check the minimum source temperature and change it if required; check source flow rate and source sizing.
Who to ask for: Ground source heat pump engineer.
What you might notice
Sources
- OPERATION AND INSTALLATION Heat pump manager WPM 3 (DM0000035521) ↗ · A 316199-43934-9674 · page 47 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026