Wiring 3 port valve to tank stat, no boiler

10 Feb 2007
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United Kingdom
I want to wire a mid-position 3 port valve to divert based on tank water temperature. When temperature is in high range it goes one way, in the low range it goes the other.
Using a tank stat from a Y Plan only two terminals to use whilst we have 3 "live" wires to the valve White, Orange and Grey. No programmer

I am trying to copy what I have seen. Fused spur to junction box, then flex from that to tank stat, flex to zone valve 1 and flex to zone valve 2 from the junction box.
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You would be better off with a Diverter valve, rather than a 3 port mid position valve.
This is plumbing electrics I know...umm I've been moved?
Thanks for that reply and I see your point, it does not want to flow to two places at once!
How would the wiring be configured based on this relatively straightforward design. I want to divert hot water to a second indirect HW storage tank once tank A has got 100% 65 degree DHW. One side would have been conventionally HW the other hot flow to rads on the three-way valve. No programmer though.
How can this be done?
The first cylinder will be heated on the cyl stat 'call for heat' terminal, the second cylinder will be heated by the valve changing over when the 'heating satisfied' terminal on the cyl stat is energised automatically when the first cyl is up to temp.

You could then have a 2nd cyl stat on the other cyl that would turn off the boiler when both are heated and up to temp.
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If you use a three port, one cylinder will always 'lead'.

Why don't you use two 2 ports and two cyl stats? Then both cylinders will get to temperature entirely independently.

You haven't stated your heat source but you could always fit a bypass valve in front of the two ports?

Are you using a fuel burning stove and are worried about the return temp causing incomplete combustion?
It would using the dreaded solar energy!
An undependable heating source, but very productive when seen in action.
It would always be backed up with an automatic boiler system though on one cylinder.
The one I have seen installed is an unvented cylinder into a combi. It diverts by the method I described. If the unvented gets to temperature it lets it direct to DHW, if not then stat closes one zone valve, opens other and sends to combi for finishing off first.
My design query is a little different with three port.
To get a 3 port valve to move from rest position to the other end without stopping/resting at mid point it would mean both the white and grey wire would need to be made live by the stat.
In normal use the white only takes it half way (room stat)and the grey the second half (cyldr. stat or programmer) If grey not live then it does not go beyond mid point
The orange is not a live going to the valve!, it is a switched live (triggered by microswitch) coming from valve to light boiler when CH only is demanded. In your case not required so it would have to be made safe.
:rolleyes: :rolleyes: :rolleyes:

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