On Fri, 2 Jan 2004 16:54:01 -0000, "Set Square"
wrote:



In your case, there is no room stat at present, so the CH demand from the
programmer goes straight to the zone valve motor. You need to intercept this
wire, and connect the switching end of your room stat in series with it. You
should be able to do this all within the airing cupboard - provided this
will give you adequate radio contact with the programmable/display end of
the stat.

It would be better to take the timing function for the CH from the
existing programmer out of the occasion completely because this type
of room controller has timing functions with setback, optimisation
etc. wihich will do a better job. I suppose there's nothing wrong
with leaving it in place but setting the existing controller to 24hr
mode to provide a permanent live.......




You should be able to trace the cables ok with your meter. In the programmer
there are 2 changeover switches - each with C, On and Off. There is very
likely a mains feed to each of the C terminals. The CH On terminal will
become live when the CH is turned on, and likewise the HW. Neither Off
terminal will be connected.

Incidentally, you should really replace the TRV on the rad in the room where
the roon stat will be with a conventional valve - otherwise you'll have two
independent control mechanisms which will fight with each other. For
example, if the TRV cuts that radiator before the room is up to the
temperature set on the stat, the stat will never operate and the system will
just run contnuously, as at present.

..andy

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