In an earlier contribution to this discussion,
Pete wrote:

Right - new problem (but I think I know the solution)

Just got the 2 port valve, and when having a look at the wire noticed
that the white didnt have an inner core (just a the plastic covering).

After checking the lid of the valve the diagram shows there is a
microswitch which just connects grey and orange when the valve is
open, thus we can fire the boiler when the HW is ON.

Am I right in thinking that this valve cannot be used without the NC
link to the pump heating?

After opening up the valve, I note that the "dummy" white cable is cut
short. I then consider swapping the relay for a SPDT, and after
looking find that one is already fitted but not wired? (why???)

I cannot connect the white wire as it is a dummy! so will need to
replace the 1m or so of flex to make a connection to the white.


[Apologies for not trimming the earlier reply - thought I had! The question
and answer *should* have looked like this, will all the previous stuff
removed].

If you're converting to a C-plan, the switch on the zone valve - which
operates when the valve opens - needs to be a changeover switch with NO,
NC and COM - otherwise it won't work. If your valve isn't like this, swap it
for one which is.

If, on the other hand, you're aiming at a fully-pumped S-plan system, with
two zone valves, the switches on those only need to be of the simple
on/off type.
--
Cheers,
Set Square
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