Medium
A9 on Viessmann Vitodens 111-W B1LD 26kW

Your boiler is set up to receive heating instructions from a smart or connected room controller, but it isn't getting a signal from that controller, so it may not be controlling the heating as intended.

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

Control mode without OpenTherm device. Communication error, OpenTherm device

From this model's manual
Verified against the Viessmann/Viessmann Vitodens 111 W B1ld 5697789 installation & service manual.
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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Related fault codes

F22View →

All 28 fault codes on the Vitodens 111-W B1LD 26kW

Seeing a different code? Every code this model can display, in one place.

0A0C1018303850515859A3b0b7b8E3E5F0F1F2F3F4F8F9FAFCFdFF

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