Medium
F7 on Saunier Duval Isofast

Your boiler is struggling to accurately measure the temperature of the hot water it is producing, so it has safely shut down the hot water supply to prevent overheating.

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

Domestic hot water sensor fault

From this model's manual
Verified against the Saunier Duval Isofast installation & service manual, page 64.
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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