Boiler sounds like it's on when it's switched off

ripplyuk

I've noticed this a few times now. Previously I thought it was the neighbours boiler I was hearing but it's not. It seems to fire up just for a couple of minutes sometimes, even though it's switched off at the controls. It doesn't produce any heat at the radiators. It just makes the same noise as if it's on.

It's a conventional boiler. I only had an old range beforehand so I'm not used to boilers at all, but I assume it's not meant to do this. Do I need to get an engineer?

Mr.Generous

do you have a hot water cylinder (tank) or is it a combi boiler? combi's pre heat the water for a faster response when you turn on a tap.

ripplyuk

I have a hot water tank. It's definitely not a combi boiler.

It's an oil boiler. I can't remember the name of it atm (and I'm too scared to go outside in the dark alone to check!) but I remember it had the name 'Bluebird' on it.

Le_Kirk

It could be just the pump. When a boiler satisfies the demand for heat, the first thing that happens is that the fuel (in your case, oil) is shut off, then the pump will keep running until the water temperature has fallen below a pre-set temperature. This is controlled by a thermocouple clipped to the return pipe. Generally thermocouples work or don't work, they don't have a "oh I'll decide not to work now ...... and now I will work" but it could be where it plugs in to the circuit board. This happened to my system and it can be very disconcerting when the boiler apparently fires up in the middle of the night. You might need someone with relevant competency or certification to check it out - not suggesting you are neither of those things!

Hoploz

I've had a problem with a switch valve on my system, which meant the boiler would be on when it should have gone off by the timer. It was a switch that controlled the hot water only, so the radiators weren't on, but the boiler was heating the water all the time and ignoring the timer. My plumber changed the switch and it's ok now.

Perhaps this is the same as yours is doing?

southcoastrgi

Le_Kirk wrote: »

It could be just the pump. When a boiler satisfies the demand for heat, the first thing that happens is that the fuel (in your case, oil) is shut off, then the pump will keep running until the water temperature has fallen below a pre-set temperature. This is controlled by a thermocouple clipped to the return pipe. Generally thermocouples work or don't work, they don't have a "oh I'll decide not to work now ...... and now I will work" but it could be where it plugs in to the circuit board. This happened to my system and it can be very disconcerting when the boiler apparently fires up in the middle of the night. You might need someone with relevant competency or certification to check it out - not suggesting you are neither of those things!

For no other reason than clarification if someone decides to google what you said, it's a thermistor not a thermocouple

ripplyuk

Thanks for all the replies. I think I'll get someone out to look at it. No doubt it won't happen whilst the engineer is here but hopefully they'll be able to sort it out.

I've never thought to check if it's heating the water. It's harder to notice as I have the water on a lot so it's never really cold. I might try to leave it to cool down completely and see if the boiler is actually heating it when it fires up on its own.

Le_Kirk

southcoastrgi wrote: »

For no other reason than clarification if someone decides to google what you said, it's a thermistor not a thermocouple

Noted, it's my engineering background, we used thermocouples for measuring temperature and controlling burners on an industrial scale and the term has stuck with me. We also used thermistors in motor windings to detect over temperature so I should know the difference really!!