On Fri, 16 Sep 2011 06:41:00 -0400, Paul Franklin
wrote:

On Thu, 15 Sep 2011 22:55:39 -0700 (PDT), Ivan Vegvary
wrote:

Want to install several X10 relay switches in the house to turn on lights remotely. This would obviate my walking across the room in the dark to get to the light switch.

Problem: The X10 switch/relay requires full power at the wall switch location. Several of my switches have only a hot leg coming into the box with no neutral. X10 docs. recommend simply running a neutral wire into the box.
Question: Most of my wiring is within the attic and some of the switches are on the exterior walls. These locations are inaccessible from the attic since this is where the roof meets the ceiling ergo providing mere inches of crawl space. It would be much easier to run the neutral wire from below (I have a generous 42" high crawl space).
Question: Does this neutral have to come from the same circuit? Can I simply come from any circuit (even a separate new circuit) and run a white neutral wire to each switch box? Does it have to be from the same phase? X10 docs. do mention that if not from the same phase, then the phases can be joined at the box.

All comments, advice and suggestions appreciated.

Ivan Vegvary


It will work if you connect any neutral, but don't do it and here's
why: Suppose you are doing some remodeling or repairs down the road.
You kill the breaker to a circuit, check with your meter to make sure
the circuit is dead and start unwiring the circuit to replace a bad
outlet say. You disconnect the neutral, and all of a sudden it's hot
because upstream somewhere you connected your X10 from a different hot
circuit to the neutral of the one that you turned off. When you break
the neutral, the X10 provides a path to the other hot leg, and the
disconnected neutral becomes hot. Yes, it's current limited by the x10
and wouldn't power a toaster say, but there's more than enough current
available to make *you* toast.

This exact situation (doorbell xfmr, not x10) happened to me and I got
a good shock. It's especially dangerous because you can check the
circuit with a meter all you want before you break the neutral, and it
won't show that it's hot (because it's not, at that time). This is
why I always treat the neutrals as hot until they are disconnected and
verified to be dead.

So bite the bullet and do this some other way. And it is against
code, if you need another reason.

HTH,

Paul F.
Can you say "red herring" or "straw man"?

When you shutt of a breaker you ONLY shut off the "line" - not the
neutral.

When you go to replace that theoretical outlet, the neutral is STILL
GROUNDED at the panel - so there is NO voltage differential between it
and ground. Also, the X10 is not a load, like a bell transformer. It
is a voltage controlled device - not current - so it is only
"injecting" a couple of milliamps into the neutral - so even IF it was
ungrounded at the panel (which would make the circuit totally
inoperative) it would be doing good to give you a little tickle -
muchless harm you.