BoilerFaultCodesYour boiler is temporarily pausing because it is producing more heat than your radiators or hot water system can currently use or circulate.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Heat demand lower than energy supplied
What causes this fault?
This occurs when the boiler generates heat faster than your central heating system can carry it away, often because too many radiator valves are turned off or the internal pump is struggling to move the water. As a safety measure, the boiler briefly pauses to allow the internal temperature to drop before attempting to fire up again. This is frequently caused by a lack of 'bypass' flow or all your thermostatic radiator valves (TRVs) closing at the same time.
This code is more common in spring and autumn when only one or two radiators are turned on, making it difficult for the boiler to shed its minimum heat output.
DIY fix possible
Ensure at least two or three radiators have their thermostatic valves (TRVs) turned up to maximum.Check that all radiator valves are open and not stuck closed.Verify that your room thermostat is set to a temperature higher than the current room temperature.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 265 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.