Hot water but no heating

[daveatrempstone]

I have a conventional boiler system, working in conjunction with a 3-port valve, room stat etc.
The hot water comes on via the programmer as normal, however the heating does not. The programmer heating light comes on to call for heat, but the boiler does not fire.
Following a previous problem, I have recently fitted a new sync motor in the 3-port valve and the system worked fine for a month or so.

Any suggestions?

 

[Agile]

You have not mention if the three port valve is working.

My expectation is that its not !

Tony

 

[daveatrempstone]

Not entirely sure whether the 3-port valve is working or not? Is it likely the problem lies with the 3-port?

 

[MANDATE]

Try calling for HW and CH, but you may need to run a little hot water from your hot tap to ensure the demand is there. If you find your radiators now begin to warm up it is because the boiler is receiving its power from the cylinder stat. As soon as the HW is satisfied the valve will or should move to the CH only positon and the boiler then receives its power from the valve (cyldr stat now satisfied), but it comes via a microswitch. The question is? does the valve move to the CH only position? if it does, suspect the microswitch.
Can't you take the actuator head off the spindle and watch the D shaped engagement hole as you try all the options. Thats what I did and found it moved correctly but there was no voltage on the orange output wire when on CH only. The problem was a faulty microswitch. Also just ensure the room stat is ok, when there is a demand for CH the white input wire to valve should be 'live', otherwise the valve can't move from the HW only position.