In an earlier contribution to this discussion,
Matthew Humphreys wrote:


Which of the connections to the valve should be live for just the hw
to be heated?


Essentially none - but the wire which is connected to Pin 8 in the junction
box will be live because Pin 8 is powered from elsewhere. Some of the others
may glow dimly on your screwdriver because they're connected via the motor
windings etc.

The valve is least active in the Hot Water only position. It sits at its
"home" (spring return) position, where it directs water only to the heating
coil in the hot water cylinder. In this position, the actuator plays no part
in switching the boiler and pump - they are switched by the cylinder stat.
--
Cheers,
Set Square
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