20104 on a Stiebel Eltron WPM heat pump manager / WPMsystem: High pressure exceeds SOA HD limit for impermissible length of time
Short answer
On a Stiebel Eltron heat pump, 20104 means: High pressure exceeds SOA HD limit for impermissible length of time. 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: High pressure exceeds SOA HD limit for impermissible length of time.
Part involved: compressor / expansion valve / pressure switches.
When it shows: High pressure exceeds SOA HD limit for impermissible length of time.
Likely causes:
- Refrigerant circuit cannot offset operating conditions to SOA range for compressor.
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
- Refrigerant circuit cannot offset operating conditions to SOA range for compressor.
Who to ask for: F-gas/refrigeration-qualified heat pump engineer (R290/A3 flammable-refrigerant competence for R290 models).
Certification: F-gas certification for fluorinated refrigerants (R410A/R454C); flammable refrigerant (R290) handling training for R290 models.
What you might notice
Sources
- WPM notification list (WPM V2.9) - multilingual; English section pp.15-26 (DOC-00081866) ↗ · WPM V2.9 · page 17 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026