20433 on a Stiebel Eltron WPM heat pump manager / WPMsystem: Major inverter fault, evaporator fan: DC link voltage too low (DCLinkVoltageLow)
Short answer
On a Stiebel Eltron heat pump, 20433 means: Major inverter fault, evaporator fan: DC link voltage too low (DCLinkVoltageLow). 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: Major inverter fault, evaporator fan: DC link voltage too low (DCLinkVoltageLow).
Part involved: compressor or fan inverter.
When it shows: Major inverter fault, evaporator fan: DC link voltage too low (DCLinkVoltageLow).
Likely causes:
- Inverter fault.
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 outdoor unit air intake/discharge is not blocked by leaves, snow or ice (air source units).
What the engineer will check
- Inverter fault.
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 20 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026