314.16 box fill question...

[DP_Fuse]

Hello all,

I am new to posting here, but after rummaging around this thread for years, I though I'd clarify something that's been bothering me. I know and understand ( I think) article 314.16 but don't understand why something like a "switch" box (ie 3x2x2.5/ 12.5 in3) can't even live up to the marketed name. Seems to me like you can't use it for anything other than an end receptacle or a basic SP switch (leg only, not fed trough). Am I wrong?

For example, 12awg BX in 3x2x2.5 "device" box assuming internal clamps used as a switch box for a feed through configuration would yield 2+2+1+1+2= 8*2.25=18in3, not allowed.

Or even a 4x2 1/8x1 7/8 handy box as a an end point for a three-way would only be OK if the neutral never sees the inside of the switch box (B+R+G+switch = 5 the maximum allowed!).

Why are these boxes so widely marketed (and used) when they seem to be almost useless. I know they can be used as pulls and JBs on smaller circuits, ect.

Thanks!
dp

 

[George Stolz]

For example, 12awg BX in 3x2x2.5 "device" box assuming internal clamps used as a switch box for a feed through configuration would yield 2+2+1+1+2= 8*2.25=18in3, not allowed.

If you figure three cables of 12-2 NM in a single gang box, you have:

6 insulated conductors
1 Equipment Grounding Conductor
1 Switch

...which amounts to 9 x 2.25 = 20.25 cubic inches of fill, provided there are no clamps in the box.

The smaller boxes aren't necessarily useless, they just can't be used everywhere. They can come in very handy at times, depending on the application.

Now, a word of caution: you have listed your occupation as an I. T. Consultant, so we are not permitted to give you how-to advice for a wiring project. That said, welcome to the forum.

 

[LarryFine]

Seems to me like you can't use it for anything other than an end receptacle or a basic SP switch (leg only, not fed trough).

Or even a 4x2 1/8x1 7/8 handy box as a an end point for a three-way would only be OK if the neutral never sees the inside of the switch box (B+R+G+switch = 5 the maximum allowed!).

Okay, you just pointed out two uses.

Weclome aboard!

 

[DP_Fuse]

I suppose

I suppose

Seems like I see an awful lot of these small boxes over filled out there. Perhaps all installed by unlicensed guys? I would doubt it since I work in a lot of new buildings. The most common thing I'm seeing is daisy-chained receptacles through handy boxes of the 12.5 in3 variety.

George, thanks for the response. Though I'm not really seeking advice, I am an I.T. consultant, but also an apprentice electrician who never finished his hours in favor of getting my E.E. Had I know I would be negatively judged for listing my occupation as such, perhaps I would simply listed one of those.

Thanks again!
dp

 

[George Stolz]

Seems like I see an awful lot of these small boxes over filled out there. Perhaps all installed by unlicensed guys? I would doubt it since I work in a lot of new buildings. The most common thing I'm seeing is daisy-chained receptacles through handy boxes of the 12.5 in3 variety.

That just seems odd to me. Can you tell how they are mounted (old or new work?)

George, thanks for the response. Though I'm not really seeking advice, I am an I.T. consultant, but also an apprentice electrician who never finished his hours in favor of getting my E.E. Had I know I would be negatively judged for listing my occupation as such, perhaps I would simply listed one of those.

Thanks again!
dp

I wouldn't say you are "negatively judged", just not in an occupation that allows how-to installation advice to be dispensed, is all. That goes for E.E.'s, E.I.T.'s, and D.I.Y.'s alike.

 

[DP_Fuse]

New work mostly. I have seen this several time recently in some pretty high-end installations. Most recently, (currently, actually) we were installing equipment in a data room where we requested no less than 10A@120V per linear wall foot in two sections of the room. The EC "forgot" and we ended up with about 2.4A plwft. In correcting this, the circuits the additional circuits they put in were still significantly less than what we asked for and were surface mounted handy boxes with 1/2" EMT between. We got a total of four more circuits, each with three receptacles and all daisy-chained through handy boxes.

Oh btw.... It passed, so the EC refused to replace them with my suggest 4in squares.