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#97698 - 03/16/06 07:33 PM Conduit fill  
tmegger64  Offline
Junior Member
Joined: Mar 2006
Posts: 7
Naples Fl.
I need your advice. As an inspector I'm getting real annoyed with not knowing how to determine conduit fill when a cable wiring method such as romex, MC, AC, etc. is installed in a conduit whether it be point A to point B, or is just protected for short runs.

I did an inspection today and the electrians (?) pulled 8/2 NM from the panel through an existing 1/2" RNC to an existing box. The RNC was secured properly at both ends. (maybe because someone else did it a few years ago). Anyway the GC said the guys were grunting and groaning and using alot of pulling compound. I told him what a shame because now they have to pull it out. They should have used THHN or the like.

Thus my question. But while typing this I was wondering if there is a Code article about using those wiring methods above if pulled from box to box also.

I'm the type if I cannot find the Code Article I cannot fail them. I may like to but I cannot.

Thanks for all your help
Tom


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#97699 - 03/16/06 08:27 PM Re: Conduit fill  
Roger  Offline
Member
Joined: May 2002
Posts: 1,716
N.C.
Tom, welcome to the forum. Your answer is in chapter 9, take notice of note 9 to the Tables

Quote
(9)A multiconductor cable of two or more conductors shall be treated as a single conductor for calculating percentage conduit fill area. For cables that have elliptical cross sections, the cross-sectional area calculation shall be based on using the major diameter of the ellipse as a circle diameter.


After determining the dimension of the cable, go to the appropriate conduit table and do the math.

As an aside, the chapter 3 xxx.22 conduit and tubing sections of the 2005 NEC clears up the question of whether cable assemblies are allowed to be installed in complete conduit systems.

Quote
Cables shall be permitted to be installed where such use is not prohibited by the respective cable articles. The number of cables shall not exceed the allowable percentage fill specified in Table 1, Chapter 9.



Roger

[This message has been edited by Roger (edited 03-16-2006).]


#97700 - 03/16/06 11:20 PM Re: Conduit fill  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,057
Estero,Fl,usa
One quick "cheat" is to measure the cable at it's widest point, go to table 5 and find the conductor closest to that approximate diameter and use the fill table for the raceway in question to see if it will <legally> fit.
I suppose if the "P" match really gets started you will need to do the math but this will certainly get you close.


Greg Fretwell

#97701 - 03/17/06 04:57 AM Re: Conduit fill  
tmegger64  Offline
Junior Member
Joined: Mar 2006
Posts: 7
Naples Fl.
Good Morning,

Thank You both for your replies it will help me to do a better inspection and justify my findings.

Thanks again,
Tom


#97702 - 03/17/06 11:45 AM Re: Conduit fill  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
Tom,
I'm not convinced that the conduit fill rules apply to short sections of conduit used for cable protection.
Don


Don(resqcapt19)

#97703 - 03/17/06 02:40 PM Re: Conduit fill  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,057
Estero,Fl,usa
Don, I think this is as close as you get to a fill rule for short sections of raceway

Chapter 9 Table note
(4) Where conduit or tubing nipples having a maximum length not to exceed 600 mm (24 in.) are installed between boxes, cabinets, and similar enclosures, the nipples shall be permitted to be filled to 60 percent of their total cross-sectional area, and 310.15(B)(2)(a) adjustment factors need not apply to this condition.

If you can't use that I don't see any relief from the normal 53% single conductor rule. (31% for 2, 40% for 3 and up)



[This message has been edited by gfretwell (edited 03-17-2006).]


Greg Fretwell

#97704 - 03/17/06 08:52 PM Re: Conduit fill  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
I'm saying that there is no fill rule for short sections of raceway used for cable protection purposes. The fill rules only apply to complete conduit systems.
Don


Don(resqcapt19)

#97705 - 03/17/06 10:18 PM Re: Conduit fill  
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
I agree with Don on this one. Because of what it says in Note #2 to Table 1.


George Little

#97706 - 03/17/06 10:18 PM Re: Conduit fill  
skingusmc  Offline
Member
Joined: May 2004
Posts: 116
Simi Valley, CA USA
resqcapt19 -

"I'm saying that there is no fill rule for short sections of raceway used for cable protection purposes. The fill rules only apply to complete conduit systems.
Don"

Who decides if it's just for protection or part of a complete conduit system?

Wonder if this should be something that is actaully address (and defined) in the NEC?

Steve


Thanks
Steve

#97707 - 03/18/06 12:12 PM Re: Conduit fill  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
IMO,
I call a conduit with a box, LB, or similar fitting on EACH END a complete system.
Conversely, a 5-10 ft. piece used to protect a NM cable down a basement wall with a box at the bottom and a bushing on the top is not a complete system.
I have "over filled" these on occasion.


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