In an earlier contribution to this discussion,
Clive M wrote:

Your best bet is to keep your semi-gravity system, but to convert it
to a C-Plan - which stops the gravity flow once the HW is hot enough
and turns off the boiler whenever neither HW or CH require heat.

As I though. HW recovery rate is ok, so main reason is control of HW
temp.


You *must* have a clear route from the boiler to the expansion pipe
with no valves in the way. You must therefore put the valve in the
short bit of pipe between the T-piece and the connection to the top
of the cylinder coil.

This would mean that the 2port *would have* to be fitted in the main
loft on the cylinder which would be a pain in the a**. I was already
going to use a RF tank stat to get from the boiler to the main loft.

It would be very much harder to go for a Y-plan because this would
require the 3-port valve to be installed in your downstairs loft -
where the CH & HW circuits split - and you would have to re-pipe
your overflow all the way from the boiler side of this junction.

As I suspected - virtually impossible to add a new pipe -

Is your problem that of having to run cables to the valve located next to
the hot cylinder? If so, there are obviously pipes which travel the required
route. Can't you run the cables alongside the pipes?

One thing I forget to mention in the previous post: If you *do* decide on an
S-Plan fully pumped system - by putting an additional 2-port valve in the
heating circuit - you will, of course, have to move the pump into the common
section of pipe near the boiler, before the circuits split.
--
Cheers,
Set Square
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