High
11 on Chaffoteaux Calydra 24 Green

Your boiler has lost the ability to measure the temperature of the water being sent to your radiators, so it has turned itself off to prevent overheating.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Central Heating thermistor faulty (open circuit)

From this model's manual
Verified against the Chaffoteaux Calydra 23 Green installation & service manual, page 17.
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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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