D_Hailsham!
You say if just the CH is on, port A of the valve will be held open by the motor. When CH is satisfied, Port A is still be held open; but there is only 50-100v on the orange wire.
As I understand it, when CH is satisfied the room stat cuts off the supply to the white wire. It's this white wire that leads direct to the orange through the second micro switch, so how can there be any voltage on the orange when HW and CH are satisfied or not on?
If my understanding is wrong I'd welcome an explanation.
I agree the grey is still live and holds the valve CH only position.
You say if just the CH is on, port A of the valve will be held open by the motor. When CH is satisfied, Port A is still be held open; but there is only 50-100v on the orange wire.
As I understand it, when CH is satisfied the room stat cuts off the supply to the white wire. It's this white wire that leads direct to the orange through the second micro switch, so how can there be any voltage on the orange when HW and CH are satisfied or not on?
If my understanding is wrong I'd welcome an explanation.
I agree the grey is still live and holds the valve CH only position.