Byron,

On Thu, 27 May 2004 13:43:33 -0400, Byron A Jeff wrote:

>...<
> I don't profess to be an electrician and I don't have a lot of experience.  I
> guess it shows. Every box I have in my 30+ YO home has hot, neutral and
> safety ground (SG). I'm just trying to envision a wiring diagram where only
> hot and switched hot (SH) are available in a box. I guess I can see it: hot,
> neutral, and SG come into the light fixture. A separate wire with hot and
> SH goes to the switch box. So there's three wires, but no neutral.

This is absolutely standard nowadays in the UK - it's known as "loop-in" wiring.  Light fittings ("ceiling
roses") have in and out connections for each of Line, Neutral, Earth, then a twin-and-Earth cable goes to the
light unit, and another twin-and-Earth goes to the switch.  The power cable goes from one rose to another,
"looping in" and out of each one, usually supplying all of the lights on one floor.  The pair going to the
switch has Line on one wire and obviously returns Switched Line on the other.  Older houses (like mine!) have
small junction boxes mounted on the celing joists doing the loop-in thing, with the ceiling roses having just
the two connections.

> BTW how is such a line (especially the white wire) supposed to be marked?

Our installed cables have red for Line and black for Neutral.  The Switched Line (black) wire has a red sleeve
(or tape!) placed on the ends to denote that it's not one you want to touch (or connect to the Neutral
anywhere!  :-)

The upshot is that our switches don't usually have a Neutral available, so X10 switches have to rely on there
being a resistive load beyond them, and get their power by leaking through it.  This means that there are X10
"light" and X10 "appliance" switches - the former are for resistive-load-only and don't need Neutral, the
latter are any-load-you-like but must have a Neutral connection.  Consequently "low energy bulbs", that are
actually flourescent lamps with electronics controlling them, can't be used with X10 "light" controllers.

Cheers,

Howard Winter
St.Albans, England

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