On Mon, 3 Oct 2005 11:31:30 +0100, "Set Square"
wrote:

In an earlier contribution to this discussion,
fred wrote:

In article , Army
writes

I wonder if anyone could confirm (or not) that I'm barking up the
right tree here. The bit I need further information on is the
wiring. Does anyone have any good pointers to where I may learn
about this?

In case you were in any doubt, the advice of Mr Square, supported by
Mr Lurch is sound, the other is er, not :-).

Indeed, in my post of 5:16pm on 1st October, I gave a reference to a
Honeywell site showing various heating plans with their associated wiring
diagrams, and explained that and S-Plan arrangement would be best - but also
explained how a Y-Plan could be adapted to suit the OP's needs if he really
wants to use a 3-port valve.

This information should be sufficient to enable any competent DIY-er to sort
out the wiring.

Hi Set Square, Lurch et all,

OP here, many thanks for all your helpful posts!

Set Square, your post at 17:16 on Oct-01 was very helpful thank you,
in particular your reference to the honeywell site was really usefull.
I've studied the wiring diagrams and that side of things is fairly
clear now. In order to further my education, a couple of questions
spring to mind if I may be so bold...

(1) Why is S-plan favoured over y-plan? Y Plan seems to be
considerably cheaper to implement (assuming a changeover stat is not
overly expensive) and neater (ie less clutter under the boiler and
disruption to pipework). Also, regarding failures, the Y plan is
never 'closed' so no chance of the pump being activated when both
circuits are off. (Clearly the boiler has a bypass if the above were
to occur on the s-plan). I guess I must be missing something here.

(2) What is a changeover stat?

(3) Why can the motorised valve(s) not be installed on the return
rather than the flow?

BTW, I don't have TRVs on any of the rads. We have lived in this
house for a year now and the system seems to hang together quite
nicely without them. In addition, most of the rads have microbore
into 'same-end' rad valves and I don't think I've seen TRVs in that
configuration before.

Thanks all


Mike