Originally Posted by Set Square

In an earlier contribution to this discussion,
Charlie Pie wrote:


Thanks all for advice so far.
As suggested both HW and CH are independent and connected to the
boiler (potterton neteheat 16-22 Mk2 F) with 28mm pipes.
The boiler supports valving according to tech help at Potterton so the
easiest option till I replace the boiler is to fit a 2 port to the HW
system.
Please excuse the dimwit questions but is this a major job, and
capping off the gravity circuit means what exactly?

It's not a *major* job, but there are a few things you need to bear in mind.
Firstly, there must be a clear - unvalved - path from the boiler to the
point where the fill and expansion pipes are connected. This usually means
that the 2-port valve needs to go very close to the HW cylinder, after these
connections. If the expansion pipe is connected too close to the cylinder to
allow this, you will need to re-jig the pipework a bit - and move the
expansion pipe connection a bit further away.

The valve must have a set of volt-free contacts which close when the valve
is open, and it must be wired up *exactly* as shown in the C-Plan diagram in
http://content.honeywell.com/uk/homes/systems.htm in order to ensure that
the boiler only runs when either the HW or CH (or both) are demanding heat,
and that the HW circuit is closed off once the HW demand is satisfied.

You will, of course, need to partially drain the system in order to fit the
valve - and then re-fill and bleed it - and top up the inhibitor -
afterwards.


--
Cheers,
Set Square
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