Re: Re: X10 central heating control

["Paul Gordon" <paul_gordon@xxxxxxx>]

>
>
>True, you couldn't run the system if there was no power, but I think he
>meant the case where the power comes back on and the computer doesn't
>reboot properly or something.  Then you'd have no heating on even
though
>it could work.
>

Ah yes, of course, that makes sense... - that's the trouble with replying
to
email in a hurry at 10PM at night whilst still at work! Thing is, I've gone
to great lengths to assure the reliability (as much as is feasible) of my
PC
based HA controller, including putting it on a UPS, and having a
hot-standby
HA PC which continuously polls the main one & takes over all critical
functions if it fails, so such a catastrophic failure is quite unlikely in
my house. - Since I put in the hot-standby, on the few occasions when my
main HA PC has failed, it has faultlessly worked as designed, and assumed
the role of the HA PC and ensured the continuity of all critical HA
functions...


>My plan is to leave the controller in place (which does have a backup
>battery in it) and put the computerised control in parallel with it.
>

My setup has ONLY the boiler's timer & thermostat. - all but a few rads
have
TRV's on them for fine tuning, but these tend to be a "set and
forget"
operation. As I have no external timeswitch or thermostat beyond what's
built in to the boiler, interfacing with them could, I imagine, be a bit
tricky...

I have given some thought to the usual stated aim of leaving the original
controls in place, and in my case I pretty much have no choice, but I'm
concerned that if wiring X10/relays in parallel with the original controls,
(without switching the original controls out of the loop), then the
automated control would only function in one or other of the boiler
states..
- IE, assuming the "original controls" are a timer/thermostat
which makes a
240V contact closure to turn the boiler ON, then if an automated control to
do the same was wired in parallel with that, then when the "original
control" had the boiler switched on (contact closed, 240V supplied),
then
the automated control would not have control of the boiler, and wouldn;t be
able to turn it OFF. - however when the "original control" had
the boiler
OFF (contact open), then the automated control would have full control of
the operation... does that make any sense?

I would be willing to forego the use of the original controls, and have
them
switched out of circuit, and then use an imput to the HA system to turn the
heating/water on & off. But for SWMBO acceptance, I would absolutely
have to
leave the original control available as a backup, but I would want them to
have to be operated manually (IE swithced back "in" by a person
in the
house), but then there's the problem of what happens when the original
controls have been switched back in as the control mechanism, and then get
left that way? (SWMBO would do this!) - suppose the day before you go off
on
a 2-week holiday, someone switched the heating back to "original
control",
and the HA system was not able to control it? I would imagine that the only
conceivable reason for switching back to original control would be because
of some kind of HA system failure such as has already been mentioned.
Therefore, I would want to be able to switch back to original control when
required, BUT also give the HA system the ability to switch it back
automatically to sutomated control as well...

ie:

HA system is fully operational - heating is under HA control, manual
operation of CH & HW is by input to the HA system.

HA system "crashes" - SWMBO flicks a switch in the kitchen and
the boiler's
original controls can now be used to operate the CH & HW

HA system comes back to full operation - HA system undoes SWMBO's flick of
the switch and takes back control of the CH & HW  to automated control.

Thereby ensuring that if we go away on holiday & leave the boiler on
its
original control, (therefore turning the heating on for 5 hours a day for
14
days when there's nobody there!), that the HA system could automatically
assume control when it comes back to life, thus saving us a hefty gas
bill...

Phew! that was a bit long-winded!

And of course, the slight problemmette with all this is that I have
absolutely no idea how to accomplish it!

I think I should go to bed now, I think I'm rambling....

Paul G.




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