Medium
545 on Viessmann Vitodens 100-W B1GA

Your boiler has detected a faulty connection in a temperature sensor for a secondary heating zone, so it has stopped that zone from heating to prevent potential damage.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Emergency function operating mode is activated for heating circuit 2: Mixer closes. Heating circuit pump is operational. Short circuit, flow temperature sensor for heating circuit 2 with mixer

From this model's manual
Verified against the Viessmann Vitodens 100 W B1ga installation & service manual, page 66.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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