Second Opinion Needed? Central Heating Automation on the cheeep..

["Ian Lowe" <ian@xxxxxxx>]

Okay,
I am looking at my Central Heating, which I am fairly certain is about as
standard as standard can be (cheap builder) I already swapped the dumb
timer
for a smart(ER) one, but the inflexibility of even this quite complex
controller is just getting annoying..

Given our current HA setup (see SWMBO thread ;) ) the prospect of bringing
the heating within the whole Web/TV Menu/Server setup is extremely
appealing..

Now, there seems to be a standard wallplate for all of these controllers.
You want to add a controller with more features, you click off the old one,
click in the new...

the faceplate looks like a pattress box, with a row of pin contacts across
the top..

the contacts are labelled:
N  L  1  2  3  4

And the helpful wiring diagram shows that "L" is the live feed,
"N" is
Neutral Return *for the timer only*, and the connectors have the following
behaviour..

1 is connected to live when the Hot Water is "off"
2 is connected to live when the Central Heating is "off"
1 is connected to live when the Hot Water is "on"
2 is connected to live when the Central Heating is "on"

This seems to be a "cover everything" setup, as our own system
doesn't make
any use of the "off" connections...

Basically, it looks like the entire function of the controller is to act as
a timed relay, throwing two switches.. (the thermostat etc are all wired
into the ratsnest control box which actually works the motorised valves etc
below this...)

Now, the point:

I have trivially automated this using two AM10's. :)

Much prodding with my multimeter, with the system in it's various states
shows me that the Neutral return from the controller does, in fact, only
allow the timer to be powered, it serves no extra purpose. Also, the
"live"
feed to this connector block is a true "live", not switched about
or
processed in any way. (all the control is on the Neutral leg of the
circuitry).

This indicates to me that the entire Heating system can be viewed as a
Black
box from this point.

I have an AM10 for each system. Plugged into the AM10, is a short lead,
which has *only* the live wired, (the system is double insulated) and the
live *only* from this is connected to the wire which used to be connected
to
pins "3" and "4" respectively.

This works nicely, and I'm rather pleased.

I would just like to know, is anyone currently sitting hand across mouth
saying "you what? My God Man, rip it out before your house catches
fire!"?

:)

Ian.