Problem with my potterton 2000 programmer?

That suggests a stuck valve - they often have a lever you can operate to push it fully over against the return spring to the CH only position. Somtimes you can latch the lever to keep it in the CH position.

http://www.wickes.co.uk/content/ebiz/wickes/invt/443033/3-Way-Mid-Position-Valve_large.jpg

Continuing good luck...

Peccavi
April 2010

Thanks for your help Peccavi, think I'll call a plumber to try and sort it out, also the other day the HW was put on constant and it heated all the radiators in the house when the CH was off.

John
April 2010

Probably something else - the route of the control signal to turn the boiler on in CH only mode is shown here...

http://www.gasheating.co.uk/Mid-Position-Valve.html

From the timer/programmer to the room stat and then to the Mid Position Valve - the Mid Position Valve motors over to the CH position and makes a microswitch. The fire-up signal is then routed to the boiler from the microswitch on an orange wire - but only when the motor has moved the valve and made the microswitch.

If the motor in the MPV fails or the valve sticks or the Microswitch fails then CH only will not work.

When Both CH & DHW are called for together the circumstances are different.

Good luck...

Peccavi
April 2010