HW OK no CH, arghhh

[vussey]

Hello, I have a Potterton Suprima 70, the hotwater works fine on the programmer, and if hit "override" or "+ 1 hour", unfortunately the CH doesn't. With the HW off, the CH timer and manual buttons have no effect, the red light comes on the timer as "CH on" but no activity on the boiler or pump. Indeed if the HW is running, i.e. I have switched it on "override" and I switch on the CH by choosing "override" , the boiler turns off. I have recently replaced the pump and 3 port valve and motorised unit complete, it's a Siemens device from Wickes....The room thermostat does click on temperature, and I have also shorted the red and yellow manually no joy...any ideas? thanks in advance

p.s. if both CH and HW are "on" the boiler doesn't go at all. The HW will only fire the boiler if it's on without the CH.

 

[Agile]

It sounds as if the motor valve may have failed!

Tony

 

[MANDATE]

I've had same problem on two occasions.
1st was due to a faulty motor, so valve never moved to CH position.
2nd The motor was ok and valve did move to CH position but boiler did not light due to a faulty micro switch.
remove actuator head and make sure valve spindle is not stiff
replacing the actuator head will cure both the above problems.

 

[vussey]

Thanks for the tips chaps, I believe I found the problem, with CH on at the programmer, there is no power to pin 1 of the room thermostat, I also can't hear the relay in the programmer clicking for CH, although it's fine on HW, so I am guessing a faulty ST6400c.

Cheers!

 

[seco services]

if you have no power to room stat from programmer. yes faulty programmer.