Central Heating not turning off in evenings.

[mottsy]

Hi all,

My central heating seems to work fine in the mornings when the hot water and heating are only on for a short time, but in the evenings when they are both on for longer the room thermostat soes not turn off the heating and it gets warmer and warmer.

The motorised valve responds when I turn the thermostat up or down manually.

I have a Potterton Performa system HE with a Drayton thermostat with 3 wires that looks like this
http://www.diy.com/nav/fix/plumbing...hermostat-24601BQ-White-9271189?skuId=9280889

Is it worth me getting a new thermostatn or is it unlikely to be the problem?

Thanks

 

[Armo74]

Sounds more like a problem with the motorised valve.

 

[mottsy]

The mechanical part of the valve seems to be working OK.
(That art was replaced about 18 months ago as the old one went stiff). So luckily, I still have a new top part with the electics in it sitting in the box.

Is it just a matter of switchg off the electrics and replacing the old one following the same wires, or is there something I need to watch for?

Thanks

Tony