High
2 flashes green on Main Insul 7

Your boiler has detected that an external safety control, such as a heating programmer or a smart thermostat, is not communicating with or is disconnected from the unit.

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

Shutdown input (BL terminals on User Interaction Controller are open circuit)

From this model's manual
Verified against the Main Boiler Ins 3 9 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 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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