Why Does My Combi Gas Boiler Make A Noise When The Central Heating Is Off?

[dave50]

It sounds as though it is running but the heating is off. Anybody any ideas please?

[jno]

sometimes it will just switch itself on for a short while to make sure water is warm when you want it. Happens around 1am for ours.

[Buenchico]

https://www.duffyheating.ie/blog/why-does-my-boiler-fire-up-randomly/

[johnk]

Ours does overrun for a while after it's switched off. I think it's to cool the boiler down before the pump switches off.

[Hopkirk]

Is it when you turn a hot tap on?

[theshedman]

Ours does that as it has a comfort setting which keeps a small amount of water warm to make it quicker when you turn on the water or heating.

[dave50]

Thank you for all your answers but the sound is constant even though the heating has been off for hours and no tap has been turned on. If I put my hand on the boiler I can feel slight vibration as though something is running.

[The Builder]

if none of the above, dave, then it's likely a fault somewhere.
Sorry if that sounds like a statement of "the bleedin' obvious" but boilers are full of little gizmos, and any one of them can cause this.

Most likely a small thermostat/thermistor fault.
Or... a stuck valve
Or... circuit board problem
Or... a controller problem.

Or... or ... etc

Best to call someone out Dave :o(

[dave50]

Thanks builder.