Type NM Cables through bored holes

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pierre

Senior Member
Question 1

There are a number of individuals where I work who insist that no more than 3 NM cables can be passed through a bored hole in wood studs.

As far as I have researched, there are no NEC requirements for this.

1. Does anyone know of a section in the NEC that I may have missed, that requires this?

2. Does anyone else run across this same situation?


Question 2

Also have individuals in this area that do not permit data cable such as Cat 3 & Cat 5 in the same bored hole as NM or AC cable.

1. Where are those requirements found in the NEC?


Question 3

CATV cable does have a 2 inch separation requirement from NM Cable as per 820.52(A)(2) ['02], 820.133(A)(2) ['05].

1. Does this tell me that CATV type cable cannot be installed through the same bored hole as NM Cable?
 

jwelectric

Senior Member
Location
North Carolina
Re: Type NM Cables through bored holes

334.80 Where more than two NM cables containing two or more current-carrying conductors are bundled together and pass through wood framing that is to be fire- or draft-stopped using thermal insulation or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).

Here is where I went to the microphone in Raleigh Tuesday of this week. Dave Mercier Technical Director for Southwire was the panelist who answered the question about 334.80 and derating and said that we would do the derating. Dave is also an Alternate for Code Making Panel Seven.

I questioned the referral from 334.80 to table 310.15 (B) (2) (a). Would it not be subject to the section 310.15 (B) (2) as outlined in the 24 inch bundling. His answer was the more restrictive rule would take presence. At break I talked future with him and in the short time allotted we agreed that I should send him an e-mail with my concerns to give a chance to research an answer but would not budge on the derating rule.
Your other questions you have already answered
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Re: Type NM Cables through bored holes

334.80 only requires derating if the hole is to be fire stopped or filled with sealing foam. I see no limit as to the size of the hole or the number of cables that may pass through it if it isn't sealed. Also, one may argue that they would also need to be bundled together for 334.80 to even apply. I know that there have been many posts regarding the question of bundling more than 24" and passing through a common hole. A quick search should provide a plethora of opinions on that one.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Re: Type NM Cables through bored holes

CATV cable does have a 2 inch separation requirement from NM Cable as per 820.52(A)(2) ['02], 820.133(A)(2) ['05].

No it doesn't. Read exception #1.

-Hal
 

jwelectric

Senior Member
Location
North Carolina
Re: Type NM Cables through bored holes

I must admit that I would be one who thought that the bundling would require a bunching of wires or cable for a distance of 24 or more inches but as Mr. Dave Mercier pointed out that bundled was not defined in 310.15 (B) (2) it was only mentioned. A definition would be found in 100 or at xxx.02 of an article, as is outlined in 520.02 Bundled. Cables or conductors that are physically tied, wrapped, taped or otherwise periodically bound together.

I have opened my eyes a little wider and look at ?bundled? a little different than ever before.
:roll:
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Re: Type NM Cables through bored holes

CATV cable does have a 2 inch separation requirement from NM Cable as per 820.52(A)(2) ['02], 820.133(A)(2) ['05].
820.133(A)(2)-This section mentions a 2" separation from conductors , would conductors be the same as a cable? IMO they wouldn't be the same.
 

ken987

Senior Member
Re: Type NM Cables through bored holes

The separation of cat 5 and RG6 for electrical lines and sources is a IEEE, or TIA standard, generally it's six to eight inches, and twelve for motors, ballasts...Been to a few home networking classes and sound system classes and they want it separated, not a NEC requirement, but good for the performance of the system.
 

pierre

Senior Member
Re: Type NM Cables through bored holes

Hal
The exception says "Nonmetallic-sheathed Type AC or UF cable"

What is Type Nonmetallic-sheathed AC cable if this is not an errata?

I am trying to be as detailed as possible with this, as I am discussing this with other inspectors who tell me these installations are all violations.

Basically I am referring to horizontal holes, through one or two studs (framing members), I should have mentioned that in my original post.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Re: Type NM Cables through bored holes

Pierre,
I think that the exception is missing a comma. Look at the same exception for 800.52(B) in the 2002 code.
Don
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Re: Type NM Cables through bored holes

Pierre,
It should read: " ...metal-sheathed, metal-clad, nonmetallic-sheathed, Type AC, or Type UF cables, ..." The comma after nonmetallic sheathed is missing in this section in both the 2002 code and the 2005.
Don
 

RAF

Member
Re: Type NM Cables through bored holes

Based on the above using the 90 degC ratings before derating, am I correct with the following?


For up and including 4 NM cables each with 2 current carrying conductors yields:

(7 - 9 conductors = 0.7 derating factor)

#12 AWG [30A * 0.7 = 21A] 20A breaker OK

#10 AWG [40A * 0.7 = 28A] 30A breaker OK {next higher standard rating of overcurrent protection device}
 
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