Heat pumps · Error codes · Stiebel Eltron
20504Stiebel Eltron · WPM heat pump manager / WPMsystem (controller platform)
20504 on a Stiebel Eltron WPM heat pump manager / WPMsystem: IWS update performed
Short answer
On a Stiebel Eltron heat pump, 20504 means: IWS update performed. The heat pump keeps running.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: IWS update performed.
Part involved: WPM/IWS firmware.
When it shows: IWS update performed.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Information only |
| Engineer needed? | No |
The heat pump keeps running.
Resetting itself: n/a.
Manual reset: n/a.
What you can check
The manual lists no checks for a homeowner. Note the code and call an engineer.
What the engineer will check
- Consult Stiebel Eltron service for this message.
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 21 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026