In an earlier contribution to this discussion,
Simon Hawthorne wrote:

On Sat, 20 Nov 2004 18:09:59 -0000, "Set Square"
wrote:

You really need a room stat in each zone, in a
room which *doesn't* have a TRV - and use this to close the
respective zone valve, and turn the pump off when both valves are
closed.

Hi SS

I do have this - two zones, two room stats - and when both stats close
the zones, the pump continues to run. There are no TRVs in the rooms
with stats - and won't be.

Do you think it could just be a simple wiring fix?

Thanks

Yes, but unless you also put a zone valve in the HW circuit, you can'e
achieve a boiler interlock - so the boiler will continue to cycle on its own
stat, and waste energy.

To fix the pump problem (i.e. simple fix without boiler interlock), it needs
to be wired thus:
The CH ON terminal on your programmer needs to be connected to the input
side of both room stats. The output side of each stat needs to connect to
the motor feed in its respective zone valve. The other side of the zone
valve motors should be connected to neutral.

Each zone valve should have a pair of "volt-free" (i.e. not connected to the
motor) contacts which close when the valve is in the open position. The COM
terminal on these contacts on both valves needs to have a permanent live
feed - or at any rate, a feed from CH ON on the programmer. The NO terminal
of both sets of contacts needs to be connected to the pump's live terminal.

The pump will then only run when either or both valves are open - which will
only happen when either or both room stats are calling for heat.

Hope this makes sense!
--
Cheers,
Set Square
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