Central heating won't go off!

elljay

My oil fired heating is set via timer to go off at around 8.15. However it hasn't!! Other than switching off at the mains it won't stop, as soon as I switch the mains back on it fires the boiler up again, even though the timer lights are all off and it's set to the off position.

Can anyone point me in the direction of which complicated bit of kit has failed so I can look to replace it? Common sense tells me it must be the timer but that was replaced not long ago apparently. Could it be anything else?

Very aggravating as now I'll have to get up in the morning and switch on, rather than waking to a warm house! Grrr!

Thanks for any guidance.

LJ

molerat

Diverter valve stuck. In simple terms the controller does not turn the boiler on it opens the valve and the microswitch, which is constantly powered, switches the boiler on. If the valve is stuck open then the boiler is powered up until the mains is turned off.

jd87

Sounds like there must be an off/timer/on switch, which obviously needs to be set to timer but you current have it set to always on.

Maybe take a photo of your control panel for people to take a look? People can't really advise without knowing what system you have.

albyota

Is the programmer / timer on the front of the boiler?

elljay

Thank you. The timer is on the wall, next to the mains switch, the boiler is on the floor. Last night I kept turning it on but the boiler fired up each time, until after leaving it off for about half an hour, suddenly when I turned it on, the boiler didn't fire up. So I left it on, with the timer in the timed position so it would hopefully come on this morning - which it did. It's due to go off at 8.15 so I'll see what happens then. It's almost as if it needed time to cool down for the timer to do its work, strange. The timer options are on constantly, timed, off constantly and an hours boost during the off periods.

I need to find out what a diverter valve looks like now . Thank you all again.

molerat

Google pictures of "3 port central heating valve". If it is working OK now it could be signs of a sticky valve. Been there done that

macman

Make and model of boiler and programmer might help...

gas4you

either the 3 port valve head, or the heating 2 port valve has failed open and on.

Look in your airing cupboard near the hw cylinder, this is the most likely place to find these valves.