On Wed, 17 Dec 2003 09:56:38 -0000, "Christian McArdle"
wrote:

If you have two (or more) room programmers, you could bring
their demand signals and connect them together, then go through
the switch, bring in the HW demand and then into the boiler.

You couldn't put the switch on the output of the programmers, as that would
short the outputs of them together, causing the zone valves to open in
unison, rather than being individually controlled. You could put the switch
on the microswitch outputs of the 2 port zone valves. However, this would
not be ideal, as if the boiler fires due to the HWC zone valve demanding
heat, then the heating zone valves may already be open, causing unwanted
heat in the radiators.

Does your last sentence make sense ? If the heating zone valves are already
open, then this can only be because one or both of their timers are on and
one or both of their stats are demanding heat. In what way is heat in the
radiators then "unwanted" ? Apart from that, yes, the outputs can only be
commoned at the boiler after the zone valves, or independent zone control
will not be achieved.

--
I have a vitally important role serving as a bad example.

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