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

["LeeUKHA" <mailinglists@xxxxxxxxxxx>]

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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