In uk.d-i-y, Rob Convery wrote:
In my living room I currently have a single light which is controlled by a
single switch.

I have put in a number of halogen lights which now all trigger off the
single switch

I am looking to put some X10 control onto these lights such that there are
two circuits: Circuit 1 controls 3 lights & Circuit 2 controls 2 lights.

I am more than happy about how to convert the single circuit to 2 with the
X10 moules turning on the lights but I would also like the old light switch
to still work i.e. flick the old light switch and it turns on both circuits

The bit I am struggling on is how to wire this is that if you put the switch
to both circuits then it will cause a short on the X10 modules thus turning
all lights on when either X10 circuit is switched on.

Is it just a case of using the switch to turn on relay triggered feeds (thus
isolating each circuit? If so would some normal 240V 3A ones be OK? i.e.
http://www.maplin.co.uk/images/Full/37495i0.jpg

I don't know about the regulatory side of things, but in practice this
would work fine. I have a similar setup for the outside lights here,
which are all turned on by a wall switch, and just some of them turned
on by a PIR.

The only limitation with
this is you could not have them dimmable.)

Is there a way of doing this keeping the main dimmer with the capability of
dimming all lights?

I'm not sure if understand you correctly but clearly the relay coil
won't respond reliably to a dimmed input signal. But there's no reason
why it shouldn't switch a dimmed signal. Could you explain more fully?

--
Mike Barnes