HD-SENSOR-MAX on a Stiebel Eltron WPM 3 heat pump manager: The high pressure sensor maximum limit has been reached
Short answer
On a Stiebel Eltron heat pump, HD-SENSOR-MAX means: The high pressure sensor maximum limit has been reached. 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: The high pressure sensor maximum limit has been reached.
Part involved: compressor / expansion valve / pressure switches.
When it shows: The high pressure sensor maximum limit has been reached.
Likely causes:
- Heating flow rate too low; selected room temperature / heating curve too high.
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 - restarts after IWS fault time/idle time.
Manual reset: after 5 faults in 2 h run: IWS 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).
- Check room thermostat / set temperatures are not set unusually high.
What the engineer will check
- Heating flow rate too low; selected room temperature / heating curve too high.
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
- OPERATION AND INSTALLATION Heat pump manager WPM 3 (DM0000035521) ↗ · A 316199-43934-9674 · page 46, 47, 50 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026