Medium
CP020 on Baxi 400 Combi 2

Your boiler is experiencing a communication error between its internal heating zones, which may cause your heating to turn on or off unexpectedly.

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

Zone function

From this model's manual
Verified against the Baxi 400 Combi 2 installation & service manual, page 53.
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

CP021View →CP022View →

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