High
1 flash green on Main Insul 7

Your boiler has shut down because the water inside is getting too hot, too quickly, or cannot circulate properly through your heating system.

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

Temperature protection (Maximum flow temperature exceeded, Flow temperature rise rate too high, Excessive difference between flow and return temperature)

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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