In an earlier contribution to this discussion,
Christian McArdle wrote:

* fit an automatic by-pass valve between the flow pipe above the
pump and the HW return - replacing the existing gate valve with a
tee (I can fit a gate valve on the inlet instead, if needed)

Personally, I would use the automatic bypass valve to "short out" the
hot water zone valve. I would also remove the balancing gate valve.
Hopefully, this will give hot water priority and the pump overrun
will dump any heat into the cylinder. This is NOT an appropriate
solution on an unvented cylinder. It should only be considered for
gravity cylinders and heat banks.

Christian.

Tha't an interesting idea. Dumping a bit of heat into the HW for a few
seconds (during pump over-run) certainly wouldn't do any harm.

Presumably you are referring to unvented *cylinders*? I assume that if I
convert the *primary* circuit to unvented, that wouldn't be a problem?

It's probably a good idea to get rid of the balancing gate valve - in fact,
I'll open it right up now to see what happens. Since I've fitted a
programmable stat on the CH, I generally heat the HW when the CH isn't on,
anyway - so there's no need for any balancing.

Can you see any other problems in what I want to do - with reference to the
pictures mentioned in my earlier post? [
http://www.mills37.plus.com/cylinder.JPG and
http://www.mills37.plus.com/cylinder2.JPG]
--
Cheers,
Set Square
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