Re: Electrical Questions

On Tue, 06 Mar 2007 19:07:17 -0500, mm <NOPSAMmm2005@xxxxxxxxxxx>
wrote:

On Tue, 06 Mar 2007 09:48:24 -0600, Mark Lloyd
<mlloyd@xxxxxxxxxxxxxxxxxxx> wrote:

On Tue, 06 Mar 2007 04:47:18 GMT, "Tom Horne, Electrician"
<hornetd@xxxxxxxxxxxxxx> wrote:

greg6755@xxxxxxxxx wrote:
3. I noticed something very interesting in a 3-way switch arrangement
in my home. To power a receptacle, they grabbed an unswitched feed
from the light fixture by connecting a black wire to both travelers in
the box. Since there is always power on exactly one of them, this
seems to work. Is this allowable ?



Yes, it's called a loop switch.

It's fairly a common way to power a switch.

It also comes in handy when you want to switch half of an outlet.

Something is missing from your description here if you connect both
travelers to a load you would have connected them to each other and the
light would be on all of the time.

A lot of people say "both" when they mean "each". Connecting to EACH
traveler wouldn't cause the same problem.

How can one connect something to each traveler without connecting to
both?

There's a three-way switch at one end fo the travelers, and the
specifiec connection at the other, right?

Having seen the diagram, I offer an alternative verbal description
of the logic. To start, there is only one traveller.

There are three conductors.
One of them is permanantly hot.
One of them is permanantly nuetral.
Neither switch affects either of these.
The outlet is connected between them.

The CENTER pole of each switch is connected to the
third-wire, the lamp, and then the other switch.
the (up) pole of each switch is connected to the hot,
and the (down) pole of each switch is connected to the nuetral.

So Switch-1 controls whether one side of the lamp is hot
or nuetral, and Switch-2 controls whether the other side
of the lamp is hot or nuetral.

If both switches are set to "hot", then the lamp
is hot, but off. If both are "nuetral" then the lamp
is not hot, and off. If the switches disagree one way,
then the lamp is hot, and it's polarity is correct,
and if they disagree the other way, then the lamp is
hot, but the polarity is reversed.

I don't know if I'd call it "stupid", it's actually
kind of clever. But if the light fixture(s) in question
have exposed shells, or if the person doing the wiring
doesn't know what you've done, it's certainly dangerous.
(I mean, you can stick your voltage detector across
the two leads to the lamp, show zero volts, and still
get zapped when you start pulling wires apart. How
much fun is that?)
.

Relevant Pages

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