A7 on a Viessmann Vitotronic 200: Solar circuit pump: Inadequate change of temperature in the DHW cylinder

What it means

The manual says: Solar circuit pump: Inadequate change of temperature in the DHW cylinder.

Part involved: Solar circuit pump.

When it shows: Inadequate change of temperature in the DHW cylinder.

Likely causes:

• No flow in solar circuit (solar circuit pump stopped).

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 voltage at the solar circuit pump connection (if solar control function integrated into terminal 212.4). Check solar circuit pump and replace if necessary.

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

What you might notice

• No hot water

Sources

• Service instructions Vitotronic 200 WO1C (5790974 GB, 2023-09) – brine/water & split variants ↗ · 5790974 VSA00002 · page 82 · Reviewed 23 September 2026

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

Reviewed: 23 September 2026