Why Does My Boiler Keep Cutting Out?

Low water pressure

If the boiler pressure has dropped below 1 bar, most boilers will cut out as a safety precaution. Check the pressure gauge and repressurise using the filling loop if needed. If the pressure keeps dropping, there is a leak in the system that needs finding.

Frozen condensate pipe

In winter, this is one of the most common causes. The condensate pipe freezes, blocks the drain, and the boiler shuts down. Thaw the pipe with warm water and reset the boiler. Lagging the pipe prevents it from happening again.

Faulty thermostat

If the room thermostat or the boiler’s internal thermostat is reading the temperature incorrectly, the boiler may think the house is warm enough and shut off early. Try turning the thermostat up by a few degrees. If the boiler stays on longer, the thermostat may need recalibrating or replacing.

Overheating

If the boiler fires up and then cuts out within a minute or two, it may be overheating. This can be caused by:

• A failed pump (water is not circulating, so the boiler heats up too fast)
• A blocked heat exchanger (sludge restricting flow - see power flushing)
• A stuck valve (water cannot flow to the radiators)

The boiler’s safety devices detect the overheating and shut it down to prevent damage. Do not keep resetting it - call an engineer.

Ignition problems

If the boiler tries to ignite but fails, it will lock out after a few attempts. This could be a faulty ignition lead, a dirty burner, or a gas valve issue. Some of these show error codes, others just result in the boiler shutting down silently.

When to call us

If the boiler cuts out more than once and a simple pressure top-up or condensate thaw does not fix it, call us on 01932 943 009. Intermittent faults can be tricky to diagnose without proper testing equipment, and repeatedly resetting the boiler can make some problems worse.