Box Fill Question

James Con

I am using the blue plastic carlon outlet boxes 18 cu in. Do I have this right.
On the box as far as fill, it says 9-14 8-12 7-10. If I am using 12/2. I have 2 blacks plus a pigtail = 3 , 2 white's plus a pigtail = 3 , 2 grounds plus a pigtail = 1 , and one outlet=2. So that's 9 > 9x2.25 =20.25. So the 18 cu in. box is no good. Now what about the wire nuts do they get factored in. Thanks

CowboyAndy

Yes, for 14AWG is 9, 12AWG is 8 and 10AWG is 7.

Pigtails I am not sure about, Hopefully someone can clarify 314.16 (B)(1) where it stated "A conductor, no part of which leaves the box, shall not be counted". Would this encompass a pigtail?

__________________

nap

Correct.

the only part I am not clear on concerning this wire count is;

you have only 2 cables entering the box, correct? and simply put, you are making joints in those cables, correct?

If so, your count is good other than the pigtails (not counted).

so, it should be 7 X 2.25=15.75. You are good to go.

CowboyAndy

7? Shouldn't it be 6?

__________________

hpp58

All grounds count as one conductor.
Clamps count as one conductor (in this case, plastic box no clamp no count)
The device that you put in the box (receptical, switch) counts as two wires.

CowboyAndy

Got it. Thanks.

__________________

hpp58

Just to make it clear
You have two 12-2 cables coming into a plastic box with a max of 8 wires allowed in the box.
The blacks count as 2
The whites count as 2
Grounds count as 1
The receptacle counts as 2
For a total of 7 wires in the box.
You only count wires entering and leaving the box.
Pigtails don't figure into the count.

CowboyAndy

So essentially, with an 18CI box, you can only have 2 cables coming into it (because of counting the device)? What is the next size up box?

__________________

handyman78

Carlon single-gang blue new-work boxes come 18, 20, 22 cu in.

__________________
Did you ever stop to think, then forget to start again?

CowboyAndy

I don't think I have ever actually looked at them. Then again, I have never had to run more than 2 caables in or out of a box.

__________________

Silk

Something else to be aware of. If you use the Carlon "Super Blue" boxes that plastic clamp for the romex instead of the cheaper ones that you knock that little square piece of plastic out of, you have to deduct 1 for the integral clamps inside the box. The cubic inch capacity is based on the UL ratings, but you will have to deduct from the stamped cubic inch capacity for proper fill to be compliant with 314.16(B)(2).

I don't believe an inspector would ever call you on it though.

James Con

Cool, Thanks for the info. Next time I will go with the 20 or 24's just to be safe for future expansion.

handyman78

Here is a link to Carlon products catalog- http://www.carlon.com/Master%20Catal...0Boxes_2B1.pdf

the Super Blue Single gang are 22 cu in. They probably try to compensate for the integral clamps with 2 cu over the standard blue boxes.

If you need more space you can also go with a double gang box and use a single opening mudring. In Lowes I have seen a single gang box with an extra side bumpout for additional space.

__________________
Did you ever stop to think, then forget to start again?

James Con

Good Idea I actually have a case of single opening mud rings from a past BX job.

James Con

Not to beat a dead horse but, I have a 4 gang box with 3 sets of 12/3 and 4 sets of 12/2. Box is 60 cu in. It will take 26- 12 ga. wires, says box. My count is 25 with wire and switches, Not including grounds. Are all these grounds considered one. This should be the last question from me about box fill. lol Thanks

Attached Thumbnails