3B on a Viessmann Vitotronic 200: Hot gas temperature: Compressor may shut down as a result of changed refrigerant circuit conditions (only heat pumps without electronic expansion valve)
Short answer
On a Viessmann heat pump, 3B means: Hot gas temperature: Compressor may shut down as a result of changed refrigerant circuit conditions (only heat pumps without electronic expansion valve). The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Hot gas temperature: Compressor may shut down as a result of changed refrigerant circuit conditions (only heat pumps without electronic expansion valve).
Part involved: Hot gas temperature.
When it shows: Compressor may shut down as a result of changed refrigerant circuit conditions (only heat pumps without electronic expansion valve).
Likely causes:
- Hot gas temperature sensor lead break.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: Not stated per code; Vitotronic messages remain until the cause is removed and are acknowledged with OK (6150133 p.82). Unremedied acknowledged faults are redisplayed the following day.
Manual reset: Acknowledge with OK on the programming unit (user level permitted per 5817913 p.56-57) after the cause is remedied.
What you can check
- Note the 2-character message code and message text shown on the Vitotronic 200 display (press OK for details) and give them to your heating contractor (operating instructions 5817913 p.56).
- You may acknowledge the message once with OK as described in the Vitotronic 200 operating instructions; if it reappears, do not keep acknowledging it - call your contractor.
- Check the heating system pressure gauge reading and report a low reading to your contractor; make sure the filling loop is closed.
What the engineer will check
- Check resistance value (Pt500A) at terminals X25.15/ X25.16 (see "Controller and sensor PCB"); replace sensor if required.
Who to ask for: Viessmann-trained heat pump engineer with F-gas refrigeration certification.
Certification: F-gas certificate (UK F-gas Regulations; Viessmann: refrigerant work by authorised refrigeration engineers only).
Sources
- Service instructions Vitotronic 200 WO1C (5790974 GB, 2023-09) – brine/water & split variants ↗ · 5790974 VSA00002 · page 70 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026