RE: X10 control of CH and HW - Y plan confusion reigns...

["Dean Smith" <dean@xxxxxxxxxxxxxxx>]

The need for the "no hot water signal" is a quirk of the Y-Plan
wiring.

I did a lot of reading when doing when my heating and at the time
understood
exactly why this was - the fine detail escapes me now but if you're happy
to
have "Nothing", "Hot Water" and "Hot Water +
Heating" you should be able to
make do with 2 appliance modules. Some older systems/controllers in fact
only give these options.

I found this diagram
http://www.eatworms.org.uk/YPlan-CentralHeatingWiring.jpg
when I was
searching but could never find the original sourc again afterwards (so
apologies to the original authors

There also some good stuff on the honeywell site that explains it aswell.
http://content.honeywell.com/uk/homes/Technical/Yplan%20Installation%20Guide
.PDF

I wired relays controlled by comfort (which can do the X10 part aswell):-
http://www.eatworms.org.uk/

Dean
-----Original Message-----
From: LeeUKHA [mailto:mailinglists@xxxxxxx]
Sent: 10 October 2004 18:54
To: ukha_d@xxxxxxx
Subject: [ukha_d] X10 control of CH and HW - Y plan confusion reigns...


A while back when I bought my current home, I replaced the (rather
knackered) CH/HW timer with a new digital one. At the time I never really
understood the wiring, but it's been working fine for a couple of years so
I
guess it was OK.

However, now I'm attempting to control the CH and HW from the HA server...

After some googling I appear to have a standard Honeywell Y-plan set up
(?).
I can get the CH to fire by shorting out two links (live into CH request?)
on the timers backplate, which I'm guessing I can simulate by having an
X10
appliance module feed 240V into that connection. But the HW I have a
problem
with, there appear to be two HW connections, one for "HW request"
and
another for "no HW request". I not sure I understand why this is,
but
shorting 240V in the MW request does not fire the boiler, when I thought
it
ought to...

What am I missing here? Can this system be automated with two appliance
modules? Will the current leak that keeps power indicators lit (like on my
elecy blanket) cause problems? Why didn't I just put cat5 to the boiler?

Any suggestion gratefully accepted...
Lee

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