41 on a Viessmann Vitotronic 200: Flow sensor HC3: Mixer heating circuit M3/HC3 is closed

What it means

The manual says: Flow sensor HC3: Mixer heating circuit M3/HC3 is closed.

Part involved: Flow sensor HC3.

When it shows: Mixer heating circuit M3/HC3 is closed.

Likely causes:

• Short circuit, flow temperature sensor, heating circuit with mixer M3/HC3.

Is it safe?

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 sensor: See mixer extension kit installation instructions.

Who to ask for: Viessmann-trained heat pump installer/service engineer.

What you might notice

• Some rooms cold

Sources

• Service instructions Vitotronic 200 type WO1C heat pump control unit (air/water split & monobloc, brine/water) (6150133, 2023-07) ↗ · 6150133 VSA00004 · page 91 · Reviewed 23 September 2026

A code explains what the controller detected, not a confirmed root cause.

Reviewed: 23 September 2026