Medium
S.39 on Glow-worm Essential

Your boiler has detected that the external sensor or switch connected to your underfloor heating system is currently open, which is preventing the boiler from activating that heating circuit.

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

Underfloorheatingcontactopen

From this model's manual
Verified against the Glow Worm Essential installation & service manual, page 34.
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

S.38View →S.40View →

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