Boiler - help

[Prudie]

We have a Baxi Solo boiler for heating and water which runs on a timer and everything seems to be working fine except - for the last month or so I've noticed that although it goes off about 10 at night and the radiators go cold the noise of it running keeps going. It's driving me mad lying in bed at night listening to it.Seems to be noticeable mainly from the loft and sounds exactly as it does when switched on. Sometimes it stops about 1.30 am with bubbling noises in the radiator, other times it's been going on all night. My OH sleeps through it all but I coulld scream in the middle of the night when I'm desperate for it to go away. Obviously somethings not right - any CH engineers out there with advice?

[The Builder]

Don't know much about these Prudie.............but it sounds like the pump is switching off (timer), but the boiler is still running....................nothing else for it......do get it looked at by a heating engineer....especially if it's overflowing into the loft!

[buildersmate]

Might this not be a symptom of the frost stat malfunctioning? - forcing the boiler into action because it reckons the temperature around the area of the boiler has got really low.
It depends where the frost stat is located and where the boiler is. You could try adjusting it - maybe it got knocked.

[Prudie]

Thank you both for your replies. Someone at work said something about frost stat but we'd not heard of it. Just to clarify the noise is that of the normal CH when it's on but it's not on. The radiators are cold, the boiler in the kitchen is not running, not even the pilot light is on and it's not making any noise. Tonight I'm going to switch the boiler off at the wall and see what happens.

[gucciman]

this is a really strange one and difficult to suggest anything without being able to examine the system in person.

i was going to agree with the builders about the frost stat until you said that the boiler isn't fired up.

the only other component thats going to make a noise is the pump, the pump would normally shut down when the programmer switches the system off, although many modern boilers utilise a pump over run stat to dissipate any latent heat from the boilers heat exchanger so perhaps that could be malfunctioning if your boiler has one.

i have come across a system that had a pump that ran constantly but that had been wired up wrongly in the first place, they don't usually start malfunctioning like that of their own accord.

is the pump for your system in the loft? next time you hear the noises during the night see if you can find your pump and and if its running, you shoud be able to feel it vibrating or hear it.

please let us know what your heating engineer finds as its good to know.

[Prudie]

Well gucciman i know nothing about how these systems work but I've thought all along it was like the pump keeps running but not doing anything. The noise is definitely from the loft not in the kitchen where the boiler is mounted in a cupboard. Would the pump be in the loft? And this frost stat where would that be whatever it is? If it's relevant the house is about 9 years old but this problem only about 6 weeks.

[gucciman]

its strange though because if the pump runs then the boiler normally does too has they are both powered from the programmer.

the pump could be anywhere to be honest but you usually find them next to the hot water cylinder or next to the boiler

if your boilers in the kitchen then it may not have a frost stat (unless it has a built in one) has they are usually only added if the boiler is in a cold room such as a garage or outhouse.

[Prudie]

Thanks again, I've been away with work for a couple of days but if anyone has anymore brainwaves the latest fact is I switched the boiler off at the mains on sat night and the noise stops immediately so got a good sleep but of course the heating's not on in the morning. Gonna have to get someone round.