Junction Box Max. Volumes?

[MadMango]

I'm not sure if this belongs here or the normal forums, so let me know if it needs to move. This is more for you electrical vs electronic people out there.

I was skimming over a NEMA document a few years ago, and I remember reading something about the maximum volume that a switch body could occupy in a junction box. This is to allow clearance for wiring and wire nuts. I've just read through WD-1, WD-6 and OS-3 from NEMA and can't find anything. Any suggestions?

"Art without engineering is dreaming; Engineering without art is calculating."

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[CorBlimeyLimey]

Do you really need the max volume, or just the min gap/clearance?

 

[MadMango]

For some reason "volume" sticks in my head, but at the end of the day, I just need to calculate how much clearance I need for several conductors and wire nuts. I can hack it, but was looking for the black & white standard to reference.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[VEBill]

I'm not a professional electrician, but I did wire my own house (more-or-less permitted, provided that a professional electrician is also involved). The Canadian standards I referred to (many years ago) listed how many conductors and a "device" (switch) are permitted in a box of a given volume. So when I installed some 4-way switches, I used larger than normal boxes because of the number of conductors (not to mention the larger 'device').

The inspector noticed that I had used the correct sized box, and he mentioned that most professional electricians don't. It was amusing how often it he pointed out that I had done things by-the-book, which was apparently very unusual.

 

[dpc]

NEC Article 314 has mind-numbing detail regarding wiring space, box volume, device fill, etc for boxes. This might be what you are thinking of. Or not.

dpc



David Castor

http://www.cvoes.com

 

[MadMango]

NEC! Thank you.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[jte]

It was amusing how often it he pointed out that I had done things by-the-book, which was apparently very unusual.

I'll second that! I would classify myself as an accomplished DIY'er WRT residential electrical wiring. Mostly replacing stuff (some wiring in my current home dates back to around 1910), but I'm also comfortable designing and wiring a new circuit but not to the extent that I'd put in a panel. I had a new sub-panel and kitchen circuits put in by a quality electrician. I noticed that he was using plastic boxes. I've always broken the tab on the box opening (equivalent of a knock-out on a metal box), but left the "cover" part as it serves the purpose of limiting the cable's movement in and out of the box. The electrician was just removing the cover, though he 'fessed up that he wasn't supposed to: "It makes it easier for us to work with and I've never been called on it by any inspector."

jt