30502 on a Stiebel Eltron WPM heat pump manager / WPMsystem: When the safety valve is open, no water flow rate can be measured via the heat pump during a function test
Short answer
On a Stiebel Eltron heat pump, 30502 means: When the safety valve is open, no water flow rate can be measured via the heat pump during a function test. 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: When the safety valve is open, no water flow rate can be measured via the heat pump during a function test.
Part involved: water flow / pump / booster heater.
When it shows: When the safety valve is open, no water flow rate can be measured via the heat pump during a function test.
Likely causes:
- Check leads and the relevant plug-in connectors, and replace if faulty. The function of the charging pump must also be tested. Test the valves in the heating circuit. Determine whether a minimum flow rate is guaranteed. Replace if faulty.
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.
- Check the outdoor unit air intake/discharge is not blocked by leaves, snow or ice (air source units).
What the engineer will check
- Check leads and the relevant plug-in connectors, and replace if faulty. The function of the charging pump must also be tested. Test the valves in the heating circuit. Determine whether a minimum flow rate is guaranteed. Replace if faulty.
Who to ask for: Heating / 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 25 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026