Too much NM cable sheath inside j-box? - DIY Chatroom

deko · 11-05-2009, 12:52 AM

I'm rewiring my garage and attic. Nothing too complicated... a few junction boxes in the attic (the attic is partially floored and accessible), some lights and outlets. I want to be sure things will pass a home inspection when it's time to sell.

I'm using blue plastic junction boxes and wondering if there is anything wrong with leaving 4 to 6 inches of NM cable folded inside the junction box (or outlet box) with the sheath unstripped.

I've read that one half inch of sheathing should be left inside junction boxes (and outlets), but is it a problem it there is TOO MUCH sheathing?

Would an inspector even check? Or Care?

frenchelectrican · 11-05-2009, 01:08 AM

Quarter to half inch sheeting inside the box is fine but NOT 4 to 6 inches it get impossible to get proper hookup with the devices.

I ran into like that many time and most inspectors in both Wisconsin and France are not too kind with it.

If you look at the photo what other members posted on other treads you will get the idea how it done in nice way.

Myself what I do every time I ran into i just strip the rest of it and clean up the box properly.

Merci,
Marc

deko · 11-05-2009, 02:45 AM

I'm not too far along on this project, but I will have to fix a couple of j-boxes.

I can hookup the devices fine--that does not appear to be a problem.

I did hear that the extra sheathing inside the box is considered a hazard... because the j-boxes are rated for so many connections and so much heat... and the sheathing is not supposed to in that equation...

AllanJ · 11-05-2009, 01:47 PM

After you staple the cables into place and put up the drywall it is very difficult to get the jacket off the cable down to the back of the box when the time comes to use the box.

Strip off the jacket first and then insert the wires into the box. You should have 6 inches of unjacketed wires.

deko · 11-07-2009, 12:52 AM

Great! Thanks for the feedback, AllanJ.

One other item I'm unsure about is using electrical tape on top of wire nuts.

Is this best practice? The idea is that the tape can prevent the wire nuts from coming loose. Someone told me that commercial work is done this way and should be done with residential as well... ??

220/221 · 11-07-2009, 01:50 AM

Quote:

but is it a problem it there is TOO MUCH sheathing?

Bothing screams handyman/homeowner like too much sheathing.

Just do it right. It's not any more difficult.

InPhase277 · 11-07-2009, 09:13 AM

Quote:

Originally Posted by deko

Great! Thanks for the feedback, AllanJ.

One other item I'm unsure about is using electrical tape on top of wire nuts.

Is this best practice? The idea is that the tape can prevent the wire nuts from coming loose. Someone told me that commercial work is done this way and should be done with residential as well... ??

Electricians very rarely tape over a wirenut. There is just no reason for it. If it is installed properly so that the wires are twisted under it, it won't back itself off.

deko · 11-07-2009, 02:35 PM

This brings up another question: How and when to twist wire?

When you say:

Quote:

installed properly so that the wires are twisted under it

Does this mean I should twist the wires before putting on the wire nut? Or just turn the wire nut hard enough on the untwisted pair so the wires end up twisted? (but then how would I know if they are properly twisted?)

If I should twist first, do I use needle nose pliers to do this? I'm running 12 gauge/20 amp NM cable. Is there some trick or tool to twist 12g wire properly?

jimkimmi · 11-08-2009, 04:22 AM

2005 nec is still the only code used by hud and most electrical inspectors i 40 of 48 states, it will tell you that 4" of free conductor is required in all j boxes. as far a the sheathing in the box 1/4 inch is required by the manufacturer of most boxes but you will need to know the maker and requirements of you specific box and the the rating of the box as far as a fire hazard does not include the small amount of sheathing all you need know is the size of the wire and calculate the cubic inch size if the box you need....a 14 cub in. box can have 3 12/2 cables or 2 12/2

**Scuba_Dave** · 11-08-2009, 10:45 AM

Quote:

Originally Posted by jimkimmi

2005 nec is still the only code used by hud and most electrical inspectors i 40 of 48 states, it will tell you that 4" of free conductor is required in all j boxes. as far a the sheathing in the box 1/4 inch is required by the manufacturer of most boxes but you will need to know the maker and requirements of you specific box and the the rating of the box as far as a fire hazard does not include the small amount of sheathing all you need know is the size of the wire and calculate the cubic inch size if the box you need....a 14 cub in. box can have 3 12/2 cables or 2 12/2

NEC 2008 has been accepted by almost every state by the end of 2009
Only 8 states left for 2010 & 2011
http://www.childoutletsafety.org/fil...doptionMap.pdf

At least 6" of free conductor is required as far as I know
4" will not cut it & may be rejected by an Inspector - mine would reject it

(3) 12-2 = 6 conductors + ground = 7* 2.25, plus 4.5 cu inches for device
That will not fit in a 14 cu inch box

(3) 14-2 = 6 conductors + ground = 7* 2, plus 4 cu inches for device
That will not fit in a 14 cu inch box either

Only CORRECT CODE can help

220/221 · 11-08-2009, 07:37 PM

Quote:

Is there some trick or tool to twist 12g wire properly?

You rarely need to twist wires.

If the wires are cut to the same length and the ends are straight, lined up (better than shown here) and held tightly together...

The wires will get twisted together nicely by the wirenut.

Wirenut only

You can pre twist with sidecutters but it is generally a pain and unnecessary. Reworking old splices with bent wires may require pre twisting.

Pre twisted

deko · 11-08-2009, 09:05 PM

Thanks for the reply.

So it sounds like twisting is desired, and the preferred way to accomplish this is to let the wire nut do it--which requires the wires to be stripped aligned properly. Is this correct?

spark plug · 11-08-2009, 10:51 PM

Quote:

Originally Posted by deko

Thanks for the reply.

So it sounds like twisting is desired, and the preferred way to accomplish this is to let the wire nut do it--which requires the wires to be stripped aligned properly. Is this correct?

We have a different "rule of thumb". Same size wire gets twisted (not with longnose") and cut to make splice even. Different size wire (12-14 or stranded to solid) is not twisted. to know when the splice is done right, is a "feel" you get after a while! (No matter what)

Don't Drink and Drive, ever!!!

**Scuba_Dave** · 11-08-2009, 11:23 PM

How do you feel about soldered connections w/stranded?
I took down some old 2 wire lights in the basement & all connections were soldered

deko · 11-10-2009, 02:41 AM

I've heard basic lineman pliers are the best tool for twisting. clipping after twisting to ensure equal lengths sounds like a nice touch.

I'm looking forward to a reply to scuba_dave's question on soldering...