On Mon, 25 Sep 2006 17:44:31 +0100, Roger
wrote:

Where do the feed and return ultimately lead to?

At present, they terminate at one radiator (which is actually not in
Zone 1 or Zone 2) The feed goes into that radiator and the return
comes from it. The boiler does have a by-pass valve too, so that if
all the rads are off, the feed will just by-pass the system and go
directly into the return, whereupon the return water temperature will
shut off the flame and pump. At least, that's how I understand it.

If to the domestic hot
water how is that controlled?

It's a combi boiler. DHW is controlled as per most combi boilers.

I am planning to insert the programmed zone valve in place of the
stopckock shown for Zone 1 (or perhaps next to it).

Replace would probably be easier. I am not sure what continuing purpose
the stop cock could have once you have a motorised valve to control the
flow. To completely isolate the zone so it could be drained down
independently would require a stop cock on both legs.

It occurred to me that I could site the zone valve in the return pipe
for the zone, opposite the stop cock which is in the feed pipe for the
zone. Then I can isolate the zone for draining purposes and plumbing
work etc. Would that be okay?

Thanks,

Mike W