Please help with annoying CH/thermostat problem

[Cobain79]

Hi,

Thanks in advance for any help you can give with this.

I recently moved house and the CH appears to have a strange problem.
When the CH is switched on by the Programmer (Potterton EP2000 I think) nothing happens (boiler doesn't fire up). The room thermostat lights up stating it is below temp. However if you then turn the thermostat all the way down (So it reports Temp reached) and back up (so it reports below) then the CH fires up. Once it has fired up it works without problem (going on and off according to the room thermostat) until it is switched off by the programmer.

The HW is working perfectly fine.

The boiler is a Potterton Suprima about 10 years old (I found an old PCB for it in the junk the previous tenants left behind but I'm not sure when this was changed). Also the room thermostat is Potterton branded.

Any ideas?

Thanks

 

[ChrisR]

SOunds like a fault with a 3 port motorised valve - wrongly wired or sticking.

 

[T&P Gas]

Cobain, recently had the same problem with my nephew's system, exactly the same boiler and thermostat. Thats where the problem was, the thermostat. It sounds like the same room thermostat, they have a light on to say when temperature is reached or below. This thermostat has what looks like a pcb board on the back of it, we changed it, problem solved, we changed it to a Drayton one, different wiring, sorted. Hope this helps.