Wiring A Switch: One NM Run Or Two Best ?

[Robert11]

Hello:

Over the years, I have done a bit of relatively simple wiring around the
house.

Have just finished reading the book by H. Richter, Wiring Simplified, 40th
ed.
with great interest. A very handy little volume.

Have the following question for those of you who might be doing
this stuff for a living, please:

Whenever I have wired a new wall switch, I have always brought a piece of NM
wire from
the source to the switch, the black going to one terminal.
Then I ran a second piece of NM with the black from the other switch
terminal to the new light fixture,
along with its white lead. (the whites would also be tied together for the
two pieces of NM at the switch box).

I see in the book (p 110) where it is apparently permissible to just use a
single piece of NM to the switch, with the white being re-marked black.
This NM would then effectively be placed in series with the normal black
wire from the source and to the fixture. (the white from the source also
going to the light fixture).

The approach i have been using which I described in the first paragraph
isn't even described in the book.

So, other than the first approach using twice the amount of NM, is there any
advantage one way or the other ?

What do you folks do in a simple situation like this ? Why ?

Thanks,
Bob

 

[Brian]

Look in your book under 1960's wiring methods. Renaming sucks.



Hello:

Over the years, I have done a bit of relatively simple wiring around the
house.

Have just finished reading the book by H. Richter, Wiring Simplified, 40th
ed.
with great interest. A very handy little volume.

Have the following question for those of you who might be doing
this stuff for a living, please:

Whenever I have wired a new wall switch, I have always brought a piece of NM
wire from
the source to the switch, the black going to one terminal.
Then I ran a second piece of NM with the black from the other switch
terminal to the new light fixture,
along with its white lead. (the whites would also be tied together for the
two pieces of NM at the switch box).

I see in the book (p 110) where it is apparently permissible to just use a
single piece of NM to the switch, with the white being re-marked black.
This NM would then effectively be placed in series with the normal black
wire from the source and to the fixture. (the white from the source also
going to the light fixture).

The approach i have been using which I described in the first paragraph
isn't even described in the book.

So, other than the first approach using twice the amount of NM, is there any
advantage one way or the other ?

What do you folks do in a simple situation like this ? Why ?

Thanks,
Bob

 

[[email protected]]

Hello:

Over the years, I have done a bit of relatively simple wiring around the
house.

Have just finished reading the book by H. Richter, Wiring Simplified, 40th
ed.
with great interest. A very handy little volume.

Have the following question for those of you who might be doing
this stuff for a living, please:

Whenever I have wired a new wall switch, I have always brought a piece of NM
wire from
the source to the switch, the black going to one terminal.
Then I ran a second piece of NM with the black from the other switch
terminal to the new light fixture,
along with its white lead. (the whites would also be tied together for the
two pieces of NM at the switch box).

I see in the book (p 110) where it is apparently permissible to just use a
single piece of NM to the switch, with the white being re-marked black.
This NM would then effectively be placed in series with the normal black
wire from the source and to the fixture. (the white from the source also
going to the light fixture).

The approach i have been using which I described in the first paragraph
isn't even described in the book.

So, other than the first approach using twice the amount of NM, is there any
advantage one way or the other ?

What do you folks do in a simple situation like this ? Why ?

Thanks,
Bob

If you want power to be available at the switch
box location (for example, for a combination
switch/receptacle) you have no choice - you must
run a cable from the source to the switch location
and a cable from there to the light.

If the above is not the case, then the physical
layout determines the best way.

An additional advantage (besides possibly using
less wire) to a switch loop versus 2 cables is box
fill. When you add a second cable, box fill
calculation increases by 4 cu in for #14 wire, or
4.5 cu in for #12 wire. A small utility box is
not code compliant for a switch and 2 cables.

Ed

 

[Paul Hovnanian P.E.]

If you want power to be available at the switch
box location (for example, for a combination
switch/receptacle) you have no choice - you must
run a cable from the source to the switch location
and a cable from there to the light.

If the above is not the case, then the physical
layout determines the best way.

An additional advantage (besides possibly using
less wire) to a switch loop versus 2 cables is box
fill. When you add a second cable, box fill
calculation increases by 4 cu in for #14 wire, or
4.5 cu in for #12 wire. A small utility box is
not code compliant for a switch and 2 cables.

Ed

Good point about the box fill. Also about needing power in the switch
box. I've retrofitted my house with X10 switches, receptacles, etc. X10
switches (switches that can be controlled either manually or remotely
via X10 commands) require a hot and neutral to the X10 switch and
provide a switched hot out to the controlled fixture. I've been caught a
few times when the existing switch had only one NM run, i.e. no neutral.
My solution was to pull in a 12-3 plus ground. One NM cable with two
hots, a neutral and a ground. The second hot (red) was used for the
switched leg.

If I were wiring my next house and I didn't mind spending a few bucks,
I'd think about running 12-3 to each switch.

 

[Roy Q.T.]

Wiring A Switch: One NM Run Or Two Best ?

Group: alt.engineering.electrical Date: Wed, Mar 30, 2005, 12:56pm
(EDT-1) From: [email protected] (Robert11)
Hello:
Over the years, I have done a bit of relatively simple wiring around the
house.
Have just finished reading the book by H. Richter, Wiring Simplified,
40th ed.
with great interest. A very handy little volume.
Have the following question for those of you who might be doing this
stuff for a living, please:
Whenever I have wired a new wall switch, I have always brought a piece
of NM wire from
the source to the switch, the black going to one terminal. Then I ran a
second piece of NM with the black from the other switch terminal to the
new light fixture,
along with its white lead. (the whites would also be tied together for
the two pieces of NM at the switch box).
I see in the book (p 110) where it is apparently permissible to just use
a single piece of NM to the switch, with the white being re-marked
black. This NM would then effectively be placed in series with the
normal black wire from the source and to the fixture. (the white from
the source also going to the light fixture).
The approach i have been using which I described in the first paragraph
isn't even described in the book.
So, other than the first approach using twice the amount of NM, is there
any advantage one way or the other ?
What do you folks do in a simple situation like this ? Why ?
Thanks,
Bob
~~~~~~~~~~~~~~>
I've come across your wiring method before, it leaves 2 uneccesary white
conductors spliced in a box. it was a color code issue, and it's been a
while since the NEC Geniuses along with Manufacturers, Electricians &
Homeowner$ decided it was a foolish demand at that level.

I'd Just run a 2 conductor cable to the switch box it seems nobody even
bothers covering the white wire black, as they say, if a guy doesn't
know what wires run through a switch he shouldn't be in there to begin
wih };-)

when you work with rigid conduit (emt) you'd run a red & a black only to
the switch., it's nice nec manners to follow color codes when & if you
practically can.

®oy

 

[Jimmie]

Hello:

Over the years, I have done a bit of relatively simple wiring around the
house.

Have just finished reading the book by H. Richter, Wiring Simplified, 40th
ed.
with great interest. A very handy little volume.

Have the following question for those of you who might be doing
this stuff for a living, please:

Whenever I have wired a new wall switch, I have always brought a piece of
NM wire from
the source to the switch, the black going to one terminal.
Then I ran a second piece of NM with the black from the other switch
terminal to the new light fixture,
along with its white lead. (the whites would also be tied together for
the two pieces of NM at the switch box).

I see in the book (p 110) where it is apparently permissible to just use a
single piece of NM to the switch, with the white being re-marked black.
This NM would then effectively be placed in series with the normal black
wire from the source and to the fixture. (the white from the source also
going to the light fixture).

The approach i have been using which I described in the first paragraph
isn't even described in the book.

So, other than the first approach using twice the amount of NM, is there
any advantage one way or the other ?

What do you folks do in a simple situation like this ? Why ?

Thanks,
Bob

I mark white wires used as hot with a piece of heat shrink tubing. Never
heard of anyone running two pieces of NM for this purpose.

 

[[email protected]]

I mark white wires used as hot with a piece of heat shrink tubing. Never
heard of anyone running two pieces of NM for this purpose.

It is done frequently, and is the most economical way
in many cases. Here's an example:
source==NM#1==Switch===NM#2==Light

Say from a receptacle box (source) to a switch directly above
it to a ceiling light. Two NM cables enter the switch box, the
whites are spliced and the blacks connect to the switch.

Ed