Boiler Keeps Switching Off

Overheating (thermal cutout activation)

If water cannot circulate fast enough, the boiler overheats and its safety cutout trips. Caused by a failing pump, sludge blockage, or limescale on the heat exchanger.

Low water pressure

Most boilers lock out when pressure drops below 0.5–0.8 bar. Re-pressurising resolves the immediate lockout, but the underlying cause must be found.

Frozen condensate pipe

In cold weather, the condensate pipe (the plastic pipe running outside) freezes, causing the boiler to lock out. Defrosting the pipe with warm water restores operation — but we can re-route it to prevent recurrence.

Faulty flame sensor

The flame sensor detects whether the burner has lit. A dirty or failing sensor causes the boiler to cut out seconds after firing, thinking ignition has failed.

Gas supply issue

Insufficient gas pressure or a partial gas supply interruption causes repeated lockouts. Our engineer checks incoming gas pressure and burner operation.

Faulty printed circuit board (PCB)

The boiler brain. Sporadic lockouts with no consistent fault code often point to a failing PCB — a more significant repair but one we can usually complete on the second visit.

Is it safe to keep resetting a boiler that keeps switching off?

Resetting once or twice to see if it was a one-off is fine. If your boiler locks out more than twice in a day, or if it smells of gas, do not reset it — call an engineer.

What does my boiler's fault code mean?

See our Boiler Fault Codes guide — we cover 140+ codes across 20 brands. Or call us and we'll look it up for you.

My boiler turns off after a few minutes every time — what is it?

This 'short-cycling' pattern is usually overheating from a circulation problem (pump, sludge, limescale) or a faulty flame sensor. Both are one-visit repairs.

How quickly can you attend a boiler lockout?

RARE targets a 2-hour response for emergency call-outs across our Central London service area, 24/7 including weekends.