Texas Residential Wireman Study Pack

Worked example: the one you'll actually see

Here's a box I've wired a thousand times. Kitchen, 14-2 in and 14-2 out, one receptacle, metal device box with internal clamps.

What's in it:

• 14-2 coming in: 1 hot, 1 neutral, 1 ground
• 14-2 going out: 1 hot, 1 neutral, 1 ground
• One duplex receptacle
• Internal cable clamps
• Grounds spliced with a pigtail to the device

Run the five categories:

1. Insulated conductors. Two hots and two neutrals = 4 conductors at #14.

4 × 2.00 = 8.00 cu in

(The grounds are not counted here — they get their own category. And the ground pigtail to the device is free, because it starts and ends in the box.)

2. Internal clamps. One allowance, largest conductor is #14.

1 × 2.00 = 2.00 cu in

3. Support fittings. None.

0.00 cu in

4. Device. One yoke, two allowances, #14 on the yoke.

2 × 2.00 = 4.00 cu in

5. Grounds. Two #14 EGCs — one single allowance.

1 × 2.00 = 2.00 cu in

Total required: 8.00 + 2.00 + 0.00 + 4.00 + 2.00 = 16.00 cu in

Now look at the box table. A 3" × 2" × 3½" device box is 18.0 cu in — that works. A 3" × 2" × 2¾" box is 14.0 cu in — that does not.

And that right there is why the deep boxes are worth carrying on the truck. A standard two-cable, one-device kitchen box needs 16 cubic inches and half the device boxes at the supply house don't have it.