High
L1 on Ideal i Combi 2

Your boiler has shut down because it thinks the water inside is getting too hot or is not moving through the system properly.

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

Flow temperature overheat lockout or no water flow lockout

From this model's manual
Verified against the Ideal I Combi 2 installation & service manual, page 56.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs when the water inside the boiler exceeds a safe temperature limit or isn't circulating correctly. The most common reasons are a failed pump that can't move the water, a blockage caused by sludge in the system, or a faulty sensor giving an incorrect temperature reading.

This issue is more frequent during the first cold snap of autumn when heating systems are turned on after being dormant all summer, which can cause internal pumps to seize.

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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