20045 on a Stiebel Eltron WPM heat pump manager / WPMsystem: Deviation between set and actual compressor speed values for a defined period of time (low pressure compressor in the case of two compressors)
Short answer
On a Stiebel Eltron heat pump, 20045 means: Deviation between set and actual compressor speed values for a defined period of time (low pressure compressor in the case of two compressors). 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: Deviation between set and actual compressor speed values for a defined period of time (low pressure compressor in the case of two compressors).
Part involved: compressor or fan inverter.
When it shows: Deviation between set and actual compressor speed values for a defined period of time (low pressure compressor in the case of two compressors).
Likely causes:
- Inverter or compressor not working correctly. Check inverter BUS connection.
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.
What the engineer will check
- Inverter or compressor not working correctly. Check inverter BUS connection.
Who to ask for: Heat pump service engineer (electrical/controls).
Certification: Qualified electrician competence for live-work on appliance electrics.
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