30399 on a Stiebel Eltron WPM heat pump manager / WPMsystem: Outdoor air temperature preheated beyond permissible range (ventilation)
Short answer
On a Stiebel Eltron heat pump, 30399 means: Outdoor air temperature preheated beyond permissible range (ventilation). The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Outdoor air temperature preheated beyond permissible range (ventilation).
Part involved: ventilation module / fans / air sensors.
When it shows: Outdoor air temperature preheated beyond permissible range (ventilation).
Likely causes:
- Cable break, short circuit or faulty sensor, no comfort temperature control, preheating coil not running or only at low output.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: unknown.
Manual reset: unknown.
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.
What the engineer will check
- Cable break, short circuit or faulty sensor, no comfort temperature control, preheating coil not running or only at low output.
Who to ask for: MVHR/ventilation-competent heat pump engineer.
What you might notice
Sources
- WPM notification list (WPM V2.9) - multilingual; English section pp.15-26 (DOC-00081866) ↗ · WPM V2.9 · page 24 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026