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#79958 02/10/02 10:51 PM
Joined: Feb 2002
Posts: 5
Junior Member
Hello out there - o.k. got quick questions.

I kinda hate NM cable and I use armored AC Minimum 12AWG for all basic installations. ( I pulled a wire out of a narrow wall once where some guy got lucky and put a long screw in a wall to hang a picture and ran it right through a NM cable, he just missed the beam and was close enough to the wire and shorted it) When running wire vertically through an existing wall (basement to 2nd floor through 1st floor wall for example) do I really need to cut open the WHOLE wall void for stapling purposes? or can I just cut out around the firestops, drill em' and run lines up?

Also is there a maximum number of lines I can put in a 14 1/2" x 3 1/2" wall void? (standard 16" on centers const.)?

I'm sure it's in the code, but code references will help me understand the lamens terms explanation vs. the code definitions. I have the 2002 NEC.

Thank you. I love this site and cannot wait to submit some interesting things for the, "what's wrong with this picture" section, with your permission.. Most of my work is upgrading and installing home office networks in houses minimum 60-100 years old...need I say more?


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#79959 02/11/02 07:39 AM
Joined: Oct 2000
Posts: 5,392

(D) Cables and Raceways Parallel to Framing Members. In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed parallel to framing members, such as joists, rafters, or studs, the cable or raceway shall be installed and supported so that the nearest outside surface of the cable or raceway is not less than 32 mm (11/4 in.) from the nearest edge of the framing member where nails or screws are likely to penetrate. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by nails or screws by a steel plate, sleeve, or equivalent at least 1.6 mm (1/16 in.) thick.
Exception No. 1: Steel plates, sleeves, or the equivalent shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing.
The intent of 300.4(D) is to prevent mechanical damage to cables and raceways from nails and screws. The Code offers two means of protection. The first method is to fasten the cable or raceway so that it is 11/4 in. from the edge of the framing member, as illustrated in Exhibit 300.3. This requirement generally applies to exposed and concealed work. The second method permits the cable or raceway to be installed closer than 11/4 in. from the edge of the framing member if physical protection, such as a steel plate or a sleeve, is provided. (A steel plate is illustrated in Exhibit 300.2.) As stated in Exception No. 1, this requirement does not apply to rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, or electrical metallic tubing wiring methods because these methods provide physical protection for the conductors.

Exception No. 2: For concealed work in finished buildings, or finished panels for prefabricated buildings where such supporting is impracticable, it shall be permissible to fish the cables between access points.

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#79960 02/11/02 02:45 PM
Joined: Dec 2001
Posts: 270
Wish I had the resources to positively answer your question. It seems to me that there would be a building code restriction about how many cables you can fish in a wall..merely because of the amount of wood that you would be punching through..resulting in both structural and fire concerns.
Obviously, in an exposed construction situation, you would have to comply with the clearance concerns addressed by the article that "sparky" quoted.

#79961 02/11/02 03:45 PM
Joined: Jan 2001
Posts: 75
310.15(B)(2)(a) Exception No. 5, and especially the last paragraph is the answer.

As a side comment, 310.15(B)(2)(b) - - - Spacing - - - shall be maintained.

It has been observed in earlier Electrical Magazines that the minimum spacing of Conduit(s) etc. is determined by the minimum spacing between the conduits secured by locknuts and bushings to boxes etc..

Maybe such thoughts could apply to MN cable.

#79962 02/12/02 04:13 PM
Joined: Oct 2000
Posts: 4,107
Likes: 3
I've got no ideas on quantity either, but we would want to be sure they are not considered as 'bundled' ... right? At some point derating should also apply, shouldn't it?

No Answers, just Questions ..

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#79963 02/12/02 09:28 PM
Joined: Dec 2000
Posts: 4,293
Do you suppose the derating should occur after the same "bundling" that occurs in a conduit nipple? (24")
This brings up something else I've wondered
Ty-wraps in MCC's or panels.(would you like to be the center wire in the bundle?)
Many of our "combo inspectors" out here don't know "JACK" about electricity, but understand airflow, heating, etc. quite well.

[This message has been edited by electure (edited 02-12-2002).]

#79964 02/13/02 07:33 PM
Joined: Feb 2002
Posts: 840
While we are on the subject of bundling, check out my pictures in "Photos submitted."

It is a common practice out West to tightly bundle all the cables right above the main panel.

Anyway, I personally dont like this practice. I always use the 3M "stackers" or an equivalent in these situations.

electure- I do think derating should apply and I always frown on the use of ty-raps in a panel. It makes for a neater job but doesnt take into account heat buildup.


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