NEC code for wire slack in the box

18 years ago

Not referring to overstuffing, but vice versa, is there a NEC code that dictates how much extra wire can terminate into a box ?

Had to change a older 220 recept. in my home today.....and this line was pulled when we 1st bought the house from a licensed electrician. There was only a bit of slack of wire in the box.

Personally, I try to leave about 6-8 inches - depending on how deep the receptacle is in relation to the box itself. Maybe it's overkill, but even for single outlets, I will use a double box with a mud ring ontop to give me extra room. If not, I'll pick up those really $$ boxes that are like 3.5" deep. Heavy as hell since all I use is steel, but it gives me ample room in the box.

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Comments (5)

randy427
18 years ago
Six inches is the standard when pulling cable in order to ensure enough slack to enable proper connections. I've often seen it cut shorter to ease getting everything stuffed into the box.
I don't know which, if any, section of the NEC calls it out.
tom_p_pa
18 years ago
Use plastic boxes...more roomier and you do not need to deal with the ground connection. The cu in capacity far exceeds metal ones. I was always a "metal" person and felt the plastic ones were inferior. However, I have been converted after doing several rooms using them. I get the super duty blue ones.
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dozer
18 years ago
NEC 2005 300.14

at least 6 inches of free conductor measured from the point the cable enters the box shall be left at each outlet, junction, and switch point for splices or the connection of fixtures or devices.

where the opening (of the box) is less than 8 inches in any direction (most boxes in common use), each conductor shall be long enough to extend at least 3 inches outside the opening.

(if there are no joints in the wire, this section does not apply)
joefixit2
18 years ago
The others are correct on the minimum, 6" from the back of the box and 3" from the outside edge, but in answer to your question, no there is no code limiting the length. You can leave as much as you want extra. It comes in handy for device changeouts in the future. Just fold them up neatly into "Z"s as you push the devices in.
Ron Natalie
18 years ago
The only time it's a real pain is in shallow boxes (#*@#%# interior walls on the second floor are framed with 2x3's, found this out the first time I tried to stick a box into the wall and it hit the back) or when using bigger dimmer/HA type switches that take up a lot of room. The latter typically come with pigtails anyhow so I go with minimal length there.