3 Port Valve - Mid Position May Be Sticking On Mixed

[thenashs]

Hi,

When our Heating and Hot Water are both being called the 3 port valve is in the correct position i.e. mid way, however tonight I noticed the house was a bit too warm. Checked the room stat and was reading above the required temperature, checked 3 port valve and it was still in the mid position and had not moved back to HW.

If the HW and Heating are on should the room stat send the signal to move the 3 port valve from mixed back to HW when the room stat has reached the required temperature?

Thanks

 

[oilhead]

If you had a HW demand, then yes, but if the HW is satisfied, then the valve will stay in the CH position, but the boiler and pump will not be switched on. Which 3 port valve is it? If Honeywell the difference between CH and Mid position is almost indistinguishable. If the valve is adjacent to the cylinder, you can check operation by operating the cylinder stat. There is also the possibility that the grey wire is fed from the switched feed instead of a permanent live. This will also give the symptom you describe.