heating on when not required

[oggymorris96]

I am working on a potterton prima f boiler with 2 x 2 port danfoss valves I am not sure which make of programmer the problem I have got is the boiler works fine on hot water when calling for demand but on the heating side there is no control the room stat is on 0 the programmer is is off and I have also removed the programmer from the wall but the boiler still fires up can you help
Thanks
oggy morris

 

[45yearsagasman]

CH valve end switch still closed. If you are qualified and"working on a Prima boiler" you should be able to work out what is wrong.
What other fault finding have you done on this system, and have you got a multimeter? Those heads are removable so you can check the valve spindle etc.

 

[oggymorris96]

Hi pete i am newly qualifid. I think i have worked it out if the ch valve has
gone to an open circuit it would then power up the boiler is that correct Gary

 

[45yearsagasman]

No, that is not correct. You have an S Plan system, and one of the switches in one of the power heads is remaining closed and sending a feed to the boiler via the orange wire. Google S plan diagram and study it to get to grips with the way it works.