In an earlier contribution to this discussion,
mike wrote:

"Roger Mills" wrote in
:


Can anyone see any problems with this arrangement?

It looks a lot like mine, only my valves are stacked vertically.

I haven't used a bypass, as I have no TRV on my hall rad where the
thermostat is, also there's a bathroom rad/towel rail.

If that's really bad, perhaps someone would tell me!


It's bad if your boiler needs pump over-run. With an S-Plan system *both*
valves close when both demands are satisfied - and if the boiler needs the
pump to keeo running for a bit after it shuts down, the water hasn't got
anywhere to go! With a Y-Plan system, there's always at *one* path open.


I'm a bit concerned about the gate valve on the return pipe - if I
read it right, ISTM it's a bit dodgy to be able to close off the
whole circulation like that - but I'm an amateur, and may be wrong,
the original installation didn't have one, so I didn't fit one.

I have a gate valve on the cylinder return at the moment, which was
installed to balance the CH and HW circuits so that when both are running at
the same time the HW doesn't hog all the flow. However, since I have
independent timing of CH and HW (uising a programmable stat for the CH) I
usually contrive not to run them at the same time - so the gate valve is
fully open. In the modified scheme it will disappear anyway - and be
replaced by a tee where the by-pass flow joins in.

My concerns about my modified arrangement are these:
1. Currently, the cylinder flow pipe only goes up as high as the top entry
point on the coil. In the new scheme, it will go higher and come down again.
I don't *think* that matters, but would welcome comments.
2. The by-pass return tees into the cylinder return rather than joining at
the same point where the CH and HW returns join. Again, I don't *think* that
matters because it will be an automatic by-pass which should only open under
pump over-run conditions - when *both* zone valves are closed - so there
*shouldn't be any scope for any obscure reverse circulation to take place.
FWIW, I'm also planning to fit a Grundfoss Alpha variable flow pump. Again,
comments will be welcomed!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!