BoilerFaultCodesYour boiler has failed to heat the hot water tank to a high enough temperature to kill off bacteria, which is a safety routine it performs periodically.
This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.
Technical description: Legionella (cause of Legionnaires’ disease) protection temperature not reached
What causes this fault?
This fault occurs when the boiler tries to perform its weekly safety cycle but fails to heat the water in your cylinder to the required 60°C within a set timeframe. The most common reason is a communication breakdown between the boiler and the hot water tank, often caused by a faulty sensor or a motorized valve that is stuck and preventing hot water from flowing to the cylinder.
DIY fix possible
Check that your hot water cylinder thermostat is not turned down too lowEnsure your hot water timer is set to allow the boiler enough time to complete a full heating cycleReset the boiler to see if the cycle completes successfully on the next attempt
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like 127 — no call-out fees, no surprises.
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