Advice on central heating problem

[ianwr]

Hi,

pulling my hair out with this one so any advice would be appreciated.

I have a fairly old central heating system that runs a back boiler. In the loft these is a hot water tank and with what looks like 2 motorized values of which one looks as if it has been replaced at some time.

My problem is that the sentral heating keeps switching off at points randomly and then switching on again randomly but then at other times i can't switch it on at all.

From my observations it looks as though the heating always comes on in

the morning when cold and then stays on for a while and at some point it the cuts off even though the timer is showing that it should be on. I can then switch off and on but it doesn't come back on. This is the same in the afternoon when it first comes on and is cold.

I have set the room thermostat in the hall way to different settings but makes no difference.Sometimes i can switch off the timer and back on and it will come back on sometimes it is all very random.

So i suspect the pump or boiler aren't problems as the system works at times. Do you think this could be a problem with the motorised values?

Thanks

ian.

[john]

Do you also have a thermostat on the hot water cylinder? If so, this could be calling for heat and getting priority.

John

[meow2222]

There are really too many possibilities, and the only way to find out is to go over the system when its refusing to heat to see whats running and what isnt. I'd start by checking John's suggestion, see if turning HW heat off brings the CH back on. Do it a few times in case its a dodgy connection near whatever youre switching on/off

NT