HEXADECIMAL-SWITCH on a Stiebel Eltron WPM 3 heat pump manager: Heat pump type DIP switch on the IWS set incorrectly (e.g. for cascade mode)
Short answer
On a Stiebel Eltron heat pump, HEXADECIMAL-SWITCH means: Heat pump type DIP switch on the IWS set incorrectly (e.g. for cascade mode). 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 DIP switch on the IWS set incorrectly (e.g. for cascade mode).
Part involved: water flow / pump / booster heater.
When it shows: Heat pump type DIP switch on the IWS set incorrectly (e.g. for cascade mode).
Likely causes:
- Isolate the heat pump from the power supply and set the DIP switch correctly.
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
- Isolate the heat pump from the power supply and set the DIP switch correctly.
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, 50 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026