NO-IWS-PARAM on a Stiebel Eltron WPM 3 heat pump manager: Heat pump type was not transferred to the controller
Short answer
On a Stiebel Eltron heat pump, NO-IWS-PARAM means: Heat pump type was not transferred to the controller. 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: Heat pump type was not transferred to the controller.
Part involved: water flow / pump / booster heater.
When it shows: Heat pump type was not transferred to the controller.
Likely causes:
- Select the heat pump type via the HEAT PUMP TYPE parameter.
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.
- Check the outdoor unit air intake/discharge is not blocked by leaves, snow or ice (air source units).
What the engineer will check
- Select the heat pump type via the HEAT PUMP TYPE parameter.
Who to ask for: Heating / heat pump engineer.
What you might notice
Sources
- OPERATION AND INSTALLATION Heat pump manager WPM 3 (DM0000035521) ↗ · A 316199-43934-9674 · page 46, 47, 51 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026