Y plan no ch

[mamamaka]

Hi, I have no heating on my y plan system, I have 240v on white wire and 0v on orange wire, calling for heating with timer and stat, what do I need to replace? Tia

 

[Johntheo5]

If you have a Y plan then 240V on the white wire should drive the valve to around mid position where the valve internal contacts change over, the lefthand contacts then provide 240V via the HW OFF contacts to droive the valve fully to the CH position and the righthand contacts provide 240V to the orange wire to fire the boiler.

 

[Echo the husky]

As above. Do you have 240v on the grey wire too?

 

[Johntheo5]

Also, to rule out a programmer/wiring HW OFF fault, put the HW heating on as well as the CH and turn down the cylinder stat, the grey wire should then be live from the HW ON contacts via the cylinderstat SAT contacts.