Inspectors opinions...(resi)

[Pierre C Belarge]

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


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?

300.17 Number and Size of Conductors in Raceways.
The number and size of conductors in any raceway shall not be more than will permit dissipation of the heat and ready installation or withdrawal of the conductors without damage to the conductors or to their insulation.


I know this section does not pertain to cables in bored holes.
I use it as guidance for making decisions on how many cables can be pulled through bored holes.
There is no restriction in the NEC as to how many cables can be installed in a bored hole.
Some judgement has to be used in the installation, such as damaging the cables during installation.

I know a lot of people including inspectors who will limit the number of cables to 3....where is that stated in the NEC.

Anyone who uses the derating argument also has no basis in the NEC for that argument.

Remember part of the requirement/restriction of ampacity adjustment.

"...where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 24in. and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as..."

There is no definition or measurement specified in the NEC in regards to spacing. It does not take much spacing for the cables to be able to dissipate heat when not installed in a raceway.

Pulling multiple cables through bored holes can be acheived without ampacity adjustment, some prudence should be observed though.

 

[infinity]

Not in Ft Myers Fl.

Why not? Do they have a local code to prohibit this? The NEC doesn't.

 

[glene77is]

Mr. Sparkie,

Be sure to count the conductors in the box.

I use a 5/8 bit, sometimes a 1/2,
and drill as many small holes as my inspector wants.
I have a 4' flexi bit for stacked studs under windows, etc.

That is my method.

 

[glene77is]

... and still get grief that it gets under my skin.

With one inspector,
I ALWAYS set one JB up in the attic with max conductors,
because I want him to have 'something' to tag me for.
I get to use up scrap Romex thatway.
He's happy with that.
Of course, I explain that there are no 'devices', so the count is within code.
We get along.
He gets to do his job, and I get to do mine.

And, as a Bonus,
he never hangs around looking very long!

 

[glene77is]

From the UL White Book

NONMETALLIC OUTLET BOXES
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.
[End Quote]

Pierre,

Thanks for the clear response.

Personally,
I would rather comply with the interpretation
on these small matters,
and not spend a lot of expensive time on the matter, and not make an extra trip on the inevitable change.
I think that playing ball makes more money on the job,
and sets up a good rapport.

On bigger issues, I politely request a code quote,
and pull out my codebook to check it on the spot.
When I get hot, tired, sweaty, I forget things and
that is when the inspector comes in very handy.
:smile:

 

[Cavie]

Why not? Do they have a local code to prohibit this? The NEC doesn't.

No local codes. Juste a Hard Nosed AHJ that sees thing differently somtimes. Easier to drill holes that fight this one. Some battles are better left for another day. This one doesn't cost much.

 

[infinity]

No local codes. Juste a Hard Nosed AHJ that sees thing differently somtimes. Easier to drill holes that fight this one. Some battles are better left for another day. This one doesn't cost much.

See's what differently? The requirement is as clear as day. Bundled for more than 24" or fire/draft stop material in the hole require derating. 100 CCC through a hole in a piece of wood do not. Do the inspectors around there get to make up their own rules?

 

[Rewire]

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?

I don't know if it is true or not but I was told by a structual engineer that boring holes in framing actually made them stronger, something to do with ROMAN ARCHES.

 

[mcclary's electrical]

wrong,,,,,bundling is only applied for more than 24",,,,,,but derating for draft and fire stop is true. I never put more than two cables in a hole to be draft stopped

 

[infinity]

but derating for draft and fire stop is true. I never put more than two cables in a hole to be draft stopped

You certainly can do it that way but even when derating #14 and #12 NM cables you need to exceed 9 CCC's before derating would change the usable ampacity of those cables.

 

[spdtrx]

I don't know if it is true or not but I was told by a structual engineer that boring holes in framing actually made them stronger, something to do with ROMAN ARCHES.

If that were true then you wouldn't need 300.4A1 and 300.4A2. 2008 NEC
and Building code 2308.9.10 and 2308.9.11