CE on a Viessmann Vitotronic 200: KM BUS extension: Functions for components connected to Example: external extension H1 are not available.; No swimming pool heating.; No switching of lag heat pumps in a cascade.; No external …
Short answer
On a Viessmann heat pump, CE means: KM BUS extension: Functions for components connected to Example: external extension H1 are not available.; No swimming pool heating.; No switching of lag heat pumps in a cascade.; No external …. 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: KM BUS extension: Functions for components connected to Example: external extension H1 are not available.; No swimming pool heating.; No switching of lag heat pumps in a cascade.; No external ….
Part involved: KM BUS extension.
When it shows: Functions for components connected to Example: external extension H1 are not available.; No swimming pool heating.; No switching of lag heat pumps in a cascade.; No external demand/blocking, external changeover of operating status, or external control of mixers and pumps.
Likely causes:
- Communication fault KM BUS external extension H1.
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 external extension H1 connections and connecting cables. Check connection aVG KM BUS (see "Controller and sensor PCB"). A fluctuating DC voltage between approx. 20 ….
Who to ask for: Viessmann-trained heat pump installer/service engineer.
What you might notice
Sources
- Service instructions Vitotronic 200 heat pump control unit (5692896, 2011-02) – 222-G/242-G/242-S/333-G/343-G/350-A ↗ · 5692896 VSA00001 · page 65 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026