On Fri, 04 Jul 2003 23:28:28 GMT, "jagerEd"
wrote:

The Web site:

http://www.hometime.com/Howto/projec...elec_4.htm#box


gives the following rules for sizing an electrical box:

1. Count the number of wires for the box. Don't count outlet/switch pigtails
and count all ground wires as one.

2. Take that number, add one for each cable clamp, and two for each device
(like a switch or outlet).

3. If the box contains only 14-gauge wires,
multiply the total by 2 cubic inches.
Or, for 12-gauge wires, multiply the total by 2.25 cubic inches.

The result is the minimum allowable volume the box should be.
Volumes are usually stamped into the back of the box on the inside.

I'm not clear on exactly what is meant by "Don't count outlet/switch
pigtails."
My guess is it means that when several wires are twisted together they count
as only a single wire.
Is that right?

No, the mean wires coming from a switch or outet connected
to the bunch of wires.


So, suppose I hav a box with switches and 4 (aluminum wire, #12) cables
attached. I know that
one of the cables is the LINE, and two go to lights in the room with the
box. I presume the fourth cable goes off to
another lighting load somewhere else in the house. So here's my count:

1. It looks like the whites are all twisted together, giving a count of 1
2. The grounds are all twisted together, giving a count of 1.
3. The LINE black is twisted with 3 other blacks, 2 going to switches and
one, I think, going to the other load. Count 1
4. The blacks in the 2 cables going to lighting fixtures each count as 1,
giving a count of 2.
5. The 2 switches give a count of 4
6. No cable clamps, as these are plastic boxes.

Total: 9

Since these are #12, the minimum box size is 2.25 x 9 = 20.25 cu. in.
The box measures 2.5 x 2.75 x 3.5 = 24.1 cu. in.

The point of all this is can I put one more cable in there to serve a new
lighting load in the room,
controlled in a separate switch box? It would seem so, because the count
does not change at all,
if I'm doing it right. Nonetheless, it seems awfully crowded in there.

TIA for you insights.

Ed