"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Alan wrote:

I plan to install a new twin-coil solar HW cylinder soon, and plan to
convert the CH system from gravity-fed to fully pumped at the same
time. (Solar coil to be utilized at a later date)
Currently the boiler and pump are downstairs with 28mm gravity-feed
pipes and 22mm CH pipes heading upstairs.
There is currently 1 thermostat downstairs, and no cylinder stat.
TRV's on all rads but 1.

I plan to utilise the original pipework where possible but move the
CH pump to upstairs and install a motorized valve to divert flow
between CH and HW. I'll also fit a cylinder stat.

I *could* also use a motorized valve to create upstairs & downstairs
zones if worthwhile.
The programmer supports fully pumped with cylinder stat and (I think)
2 zones - will check.

Any recomendations from the group of which CH plan to go with and
whether it's worth creating upstairs & downstairs zones?

Any suggestions on plumbing config and type of motorized valves to
use?
Thanks in advance,

Alan.

A lot depends on the layout of the existing pipework. Presumably there are
4 connections to the boiler at present - 2 for the HW and 2 for the CH? If
you go fully pumped with a single pump, you'll only need 2 - although you
could keep separate returns, and have 3, if that was easier.

How is the downstairs CH circulated? Is it below the downstairs floor so
that the CH pipes going upstairs are only for the upstairs rads, or does
it *all* go up and then come down to each individual downstairs rad?

If you have a single pump upstairs, *everything* (including the water for
the downstairs rads) has to go up, and then be distributed using zone
valves - probably in the airing cupboard. The ease with which this can be
achieved depends on the current setup.

If it is difficult to achieve this, an alternative fully pumped strategy
is to keep the existing pipes and simply insert a second pump into the HW
circuit. You would control the pumps with the respective room and cylinder
stats, and you then need a bit of relay logic to turn the boiler on
whenever either pump is running. You would also probably need an
anti-gravity valve in the HW circuit to prevent any flow when the HW pump
isn't on.

Assuming that a single pump solution *is* viable, an S-Plan+ system would
give you the most flexibility - and allows you to have as many zones as
you wish. Whether or not it's worthwhile having separate up and down zones
really depends on how you use the rooms. If there are long periods when
you only want to heat upstairs but not downstairs, and vice versa, then it
is a good idea. However, you need to consider whether the bathroom needs
to be warm all the time. Going back to the question how about the CH is
distributed, if you have a single 'between the floors' circuit it will be
very difficult to have up and down zones. On the other hand, if they're
already separate, you'll have to solve the problem of getting the
downstairs radiator water upstairs and back down again.

If you *do* go for zoning, I would recommend using a programmable
thermostat for each heating zone. It doesn't then matter whether the main
programmer supports zoning - you just leave the CH control on that set to
'on', and use the programmer to time just the HW.

For an S-Plan plus system, you'll need one 2-port valve per zone - so
that's one for the HW and probably two for the CH. They need to have
auxilliary 'volt-free' contacts which can be used to switch on the boiler
and pump whenever one or more of the valves are open - as per the standard
S-Plan arrangement. [See
http://content.honeywell.com/uk/homes/systems.htm ]

Any reputable make of valve - Danfoss, Drayton, Honeywell, etc. - should
be ok. Even if you use the existing 28mm flow and return pipes from the
boiler to the airing cupboard, I assume that you will use 22mm after the
pump - so the valves only need to be 22mm.

HTH.
--
Cheers,
Roger
______

Roger,

Thanks for the informative response.
There are 3 pipes into the boiler - the return from the gravity circuit goes
in via a "Y" piece with the CH return.
I will need to cap off the current gravity output from the boiler and just
use the remaining 2 connections.

The output of the pump is teed and one leg feeds the downstairs CH circuit
and the other goes upstairs on one of the 22mm pipes.
Adding a 2nd pump isn't an option I had previously thought of, however from
what you say I can achieve what I need to with 2 or 3 valves.
The pipework for downstairs is all below floorboard level and starts and
ends by the boiler, so converting to seperate zones would be reasonably
easy, but as every room is used daily there may not be much point.

I will look at the S-Plan+ details, sounds like it's what I need.

Many thanks,

Alan.