Box Fill

[LarryFine]

I need some clarification please. Art. 314.16 (2) clamp fill. Would someone explain the portion of this section that says: "Conductors that originate within the clamp assembly shall be included in the conductor fill calculations covered in 314.16 (B) (1) as though they entered from outside the box" I don't know if I've ever seen a conductor that originated from a clamp assembly??? If I'm missing something obvious here I'll feel pretty dumb!

As a literalist, it sounds like they mean a piece of cable put in a connector to take up space.

 

[wwhitney]

Possibly a mobil or prefab home type receptacle?

If you crossed that with a regular double gang box, so you have room on one side for a regular device, and there were pigtails from the cable terminations on the prefab side into the open space in the other gang, that would fit the description as I understand it.

Or maybe a prefab type receptacle with an adjoining wiring compartment to allow additional cable connections beyond 1 in 1 out.

Cheers, Wayne

 

[Dennis Alwon]

Do you not think they are talking about what I posted in post #20 which I will repost here

 

[Rick 0920]

I have been taught and always assumed those non metallic boxes with clamps for NM cable are marked with clamp deduction(s) built into the marked volume. All you need to do is count the grounds as one and devices as two conductors toward the fill.

That could be wrong, if so it only effects your conductor count by one of the largest conductors in the box though.

Most nonmetallic boxes made today provide a "clamping" style of opening for the cables provided as long as you don't break out the entire plastic pieces. They provide enough pressure to the cable and are angled inward to the cable to keep it from being pulled back out. Not all single gang boxes have these. Some of them have openings that are intended to break out. I guess that's why they require them to be stapled within 8" from the box while the other boxes can be stapled within 12" of the box. In the 2020 NEC, EGC's have been revised. If you have up to (4) EGC's present, a single volume allowance shall be counted. Additional EGC's over 4, a 1/4 volume allowance shall be counted.

 

[kwired]

Most nonmetallic boxes made today provide a "clamping" style of opening for the cables provided as long as you don't break out the entire plastic pieces. They provide enough pressure to the cable and are angled inward to the cable to keep it from being pulled back out. Not all single gang boxes have these. Some of them have openings that are intended to break out. I guess that's why they require them to be stapled within 8" from the box while the other boxes can be stapled within 12" of the box. In the 2020 NEC, EGC's have been revised. If you have up to (4) EGC's present, a single volume allowance shall be counted. Additional EGC's over 4, a 1/4 volume allowance shall be counted.

Was not aware of that.

An attempt to fix something but maybe not the correct method??

My experiences a small box does seem to get crowded fast and it may make a difference there, something like a 4 gang box often seems to have quite a bit of room in it though and may not be so necessary to require the grounds to count at higher rate.

JMO.