57 on a Stiebel Eltron LWZ 5/8 CS Premium, LWZ 5 S Plus, LWZ 5/8 S Trend, LWZ 5 S Smart: Sensor to measure the oil sump temperature
Short answer
On a Stiebel Eltron heat pump, 57 means: Sensor to measure the oil sump temperature. 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: Sensor to measure the oil sump temperature.
Part involved: compressor / expansion valve / pressure switches.
When it shows: Sensor to measure the oil sump temperature.
Likely causes:
- Sensor fault.
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: no.
Manual reset: unknown.
What you can check
- Note the fault number shown on the programming unit display.
- Check the appliance breakers/MCBs at the consumer unit are on.
What the engineer will check
- Replace the sensor.
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
- COMMISSIONING AND NOTIFICATION LIST LWZ 8 CS Premium / LWZ 5 CS Premium / LWZ 5 S Plus / LWZ 8 CS Trend / LWZ 8 S Trend / LWZ 5 S Trend / LWZ 5 S Smart (doc-00081766) ↗ · A 338916-45679-9862 · page 19 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026