C5 on a Viessmann Vitotronic 200: Power-OFF: Compressor stops
Short answer
On a Viessmann heat pump, C5 means: Power-OFF: Compressor stops. The heat pump stops until the fault clears or is reset.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Power-OFF: Compressor stops.
Part involved: Power-OFF.
When it shows: Compressor stops.
Likely causes:
- Power-OFF active (triggered by power supply utility).
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Information only |
| Engineer needed? | No |
The heat pump stops until the fault clears or is reset.
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 heat pump breaker/isolator in the consumer unit is ON (do not repeatedly reset a breaker or RCD that keeps tripping).
- If this is a "Power-OFF" message from your electricity supplier the heat pump restarts automatically when the block ends - no action required.
What the engineer will check
- No action required. If the message is constantly present: Check connection at terminal X3.7 (feed) first, then at terminal X3.6 (230 V~) (see "Cross connect ….
Who to ask for: Viessmann-trained heat pump engineer / qualified electrician.
Certification: Qualified electrician for work on electrical equipment (Viessmann safety instructions).
What you might notice
Sources
- Service instructions Vitotronic 200 type WO1C heat pump control unit (air/water split & monobloc, brine/water) (6150133, 2023-07) ↗ · 6150133 VSA00004 · page 103 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026