Inspectors opinions...(resi)

[Mr.Sparkle]

I wanted to know what some of the inspectors here think of a couple of things I have been "called on" in the past.

On carlon nm plastic boxes, well for this example single gang carlon (blue 18's or 22's) for your basic feed in/out receptacle I put both nm's in one side, I find nothing wrong with it and I believe somewhere in the NEC (I looked quickly in 314 but am typing as I look so typing wins...) it states that each opening in an NM box is designed to accommodate more than 1 NM cable. On a side note, I have also put 5 nm's in the top of a plastic 2 gang as well & see nothing wrong with it. (4 openings, you see what I mean.)

And here is another tricky one, typically in res work I use a 7/8 bit. I see no problem with say... three 14/2's and two 14/3's in the same hole, it was not hard for me to get the nm in there and each wire can move relatively freely when tugged upon, yet I have had inspectors that think otherwise.

Opinions?

 

[kbsparky]

Does the electrical inspector expect you to drill more holes in the framing, thus weakening the structure? Would the framing inspector prefer you drill less holes?

Have they communicated with each other about this conflict?

 

[infinity]

If the cables fit through the hole without damage what could the inspector actually complain about?

 

[Mr.Sparkle]

I agree with both of your logic, this is not a current problem, it is just something that I was thinking about being that I have a job coming up in a town where I know the EI, as well as other inspectors are notorious for "digging in". I have not done work in the town since I worked for another EC, but I have nothing but painful memories. (FWIW, talked to the GC today and he waited 19 days to fail his open deck inspection because he had temp plywood on the front porch deck leading to the wheelchair ramp which the HO's mother needs..........wow)

 

[vinster888]

more than 3 wires per hole

334.80 Ampacity. The ampacity of Types NM, NMC, and
NMS cable shall be determined in accordance with 310.15.
The ampacity shall be in accordance with the 60?C (140?F)
conductor temperature rating. The 90?C (194?F) rating
shall be permitted to be used for ampacity derating purposes,
provided the final derated ampacity does not exceed
that for a 60?C (140?F) rated conductor. The ampacity of
Types NM, NMC, and NMS cable installed in cable tray
shall be determined in accordance with 392.11.
Where more than two NM cables containing two or
more current-carrying conductors are installed, without
maintaining spacing between the cables, through the same
opening in wood framing that is to be fire- or draft-stopped
using thermal insulation, caulk, or sealing foam, the allowable
ampacity of each conductor shall be adjusted in accordance
with Table 310.15(B)(2)(a) and the provisions of
310.15(A)(2), Exception, shall not apply.
Where more than two NM cables containing two or
more current-carrying conductors are installed in contact
with thermal insulation without maintaining spacing between
cables, the allowable ampacity of each conductor
shall be adjusted in accordance with Table 310.15(B)(2)(a).

 

[Dennis Alwon]

And here is another tricky one, typically in res work I use a 7/8 bit. I see no problem with say... three 14/2's and two 14/3's in the same hole, it was not hard for me to get the nm in there and each wire can move relatively freely when tugged upon, yet I have had inspectors that think otherwise.

Opinions?

Firstly I find it hard to believe that 3 14/2 along with 2 14/3 nm cables was an easy install in a 7/8" hole. Four NM cables is tight. That being said if the hole goes between floors where fire caulking is used then you must derate. 334.80 2nd paragraph. Assuming all your conductors are ccc then you have 12 CCC in the hole and must derate based on 310.15(B)(2).

 

[wirenut3]

Some inspectors apply the code against bundling conductors together and accordingly ask you to derate the ampacity of your cable - based on the number of current carrying conductors- after you exceed the count of two current carrying conductors. 334.80 and 310.15(b)2.

 

[infinity]

You can put 20 cables through a hole that is not fire or draft stopped and derating still would not apply.

 

[MrMilbank]

The methods depicted in several of my residential wiring books show that multiple 5/8" holes staggered .*.*. <--like that causes less fatigue to the structure compared to one larger hole. plus using a smaller bit size cuts down on having too many conductors bundled together. and the thing about the carlon boxes: I use 1 conductor per opening until I run out of openings. Then I double up. usually I max out the box fill before I have to double up in one hole. if an obstruction prevents the use of one of the holes then an inspector should understand. It just looks neater having each hole represent a in or out or switch leg. electrical work is a craft and workmanship is required to be qualified.

 

[Ken9876]

http://www.carlon.com/Master Catalog/Zip Boxes_2B1.pdf

Carlon lists the box as having cable clamps, on another FAQ page:

How many cables can you put in one integral cable clamp?

One. The National Electrical Code section 314.17(c) Exception allows you to put
multiple cables through a knockout, but only one is allowed through each clamp.

http://www.carlon.com/FAQs/FAQ-ZipBoxes.pdf

 

[Cavie]

You can put 20 cables through a hole that is not fire or draft stopped and derating still would not apply.

Not in Ft Myers Fl.

 

[sethas]

i have always been of the impression that on a single gang plastic nail on box, that was a knockout, not a cable clamp. therefore i have always applied 314.17(C), and fastened the cable within 8".

applying that logic, two would be fine, although i like to only use one per opening.

 

[Ohmy]

You can put 20 cables through a hole that is not fire or draft stopped and derating still would not apply.

Why if its caulked?

 

[Mr.Sparkle]

Ok, thanks for the info Ken.

I do see that they call the crappy tabs in those SG's cable clamps, not that I agree with it at all....2 gangs etc...ok I'll take it, but the silly tabs in the n/o SG's c'mon......

It looks like I will no longer put more than one nm per "cable clamp".

And as far as the 7/8" hole, I am not talking about cramming those wires through multiple rafters or a horizontal wall run, I am speaking for the most part of the top or bottom plates, usually 2 1/4"-4 1/2" max in thickness, and I take quite a bit of pride in my work so it is not "forced" by any means, if it is I drill another hole. It is when I know from field conditions that the conductors are not stressed and still get grief that it gets under my skin.

 

[Ken9876]

I do see that they call the crappy tabs in those SG's cable clamps, not that I agree with it at all....2 gangs etc...ok I'll take it, but the silly tabs in the n/o SG's c'mon......


I agree., I had called P&S about this once but those boxes have a clamp, I'd call them and check.

 

[celtic]

I've got no problem with your methods Mr.Sparkle

...I do the same thing.

http://www.carlon.com/Master%20Catalog/Zip%20Boxes_2B1.pdf

Carlon lists the box as having cable clamps, on another FAQ page:

How many cables can you put in one integral cable clamp?

One. The National Electrical Code section 314.17(c) Exception allows you to put
multiple cables through a knockout, but only one is allowed through each clamp.

http://www.carlon.com/FAQs/FAQ-ZipBoxes.pdf

If you read on....

The single gang nonmetallic box, B120A does not have integral clamps,
only knockouts. For nonmetallic-sheathed cable, Romex, is a clamp where
the cable enters the box required?
Clamps are not required for single gang boxes.
See:
- 314.17(C) Exception of the 2002 NEC
- 370-17(c) Exception of the 1999 NEC.

 

[Mr.Sparkle]

Ohhhh yeah baby, I'm back to my old ways thanks to Celtic! (at least with the single gangs.)

The n/o SG blues contain knockouts, not cable clamps. Right from their own literature. Reading is Fundamental.

 

[celtic]

Ohhhh yeah baby, I'm back to my old ways thanks to Celtic! (at least with the single gangs.)

I spin/twist that silly little tab...one NM on each side of it :smile:

 

[220/221]

I have had inspectors that think otherwise.

I rarely run into thse kind of morons. When I do, I simply ask for a code reference in writing. If they give it to me, I comply and I learn something. If they won't give it you me, I am quite stubborn.

If the cables fit comfortably into the holes or KO's, there is no problem and the installation is safe. A little common sense goes a long way.

 

[Pierre C Belarge]

From the UL White Book

NONMETALLIC OUTLET BOXES (QCMZ)

SINGLE-GANG BOX​

A box nominally 2-1/4 by 4 in. or smaller is intended for one or more
nonmetallic sheathed cables to enter through a single or multiple stage​

knockout opening.



NEC

314.17(c) Nonmetallic Boxes and Conduit Bodies.
Exception:
Multiple cable entries shall be permitted in a single cable knockout opening.