High Lockout
919 on Ideal Response SE

Your boiler has shut down because the water returning to the unit is too hot, typically meaning the heat isn't being distributed around your home 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.

Technical description

Maximum temperature - Return temperature T2 too high

What causes this fault?

This fault occurs when the water traveling back into the boiler is nearly as hot as the water leaving it, indicating that heat isn't being transferred to your radiators. The most common reasons are a failed pump that isn't circulating the water or a blockage in the system, such as a build-up of sludge or closed radiator valves.

This fault often appears when heating is first turned on after summer, as pump components can seize up during long periods of inactivity.

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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