Lockout vs normal cycling
Boilers switch on and off as the house reaches temperature – that's normal. A lockout is different: the boiler stops completely, often with a fault code or a warning light, and needs resetting.
Common causes
Frequent shutdowns are often caused by:
- Low system pressure
- A frozen or blocked condensate pipe
- Overheating due to sludge, a pump problem or closed valves
- A thermostat in the wrong place, switching the heating off too early
- Ignition or flame detection faults
- An oversized boiler cycling on and off rapidly
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What to do
Check the pressure, look for a fault code and, in freezing weather, check the condensate pipe. Reset once if the manual allows. If it keeps happening, call a Gas Safe registered engineer.
