Residential wiring in NC

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reel-break

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Here`s the deal I wire a house drill a 2" hole under panel my cables come through up to panel.I also place a conduit in so after mechanical guy comes and places units I can access or pull my wires for these systems.I`m thinking 312.5c will stop this.But also where the cables come from under house to panel they are in a sense bundled for approx. 2 ft how do I know if I must derate for bundling?And could someone explain the process. Thanks
 
Re: Residential wiring in NC

310.15(B)(2)(a).
...or where single conductors or MULTICONDUCTOR cables are stacked or bundled longer than 24 inches without maintaining spacing and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a).
Reference the table to see what percentage to reduce the ampacity by and you are good to go.
Exception 5 is not for NM cable.

Pierre
 
Re: Residential wiring in NC

I had read somewhere that stacked or bundled was interpeted as touching each other continuosley for said 24"

So it would follow that any means of seperating conductors , even briefly of the 24" rule , would achieve compliance correct?

I've used that cheap foam pipe insulation to do this bettween joists

as our litigant community would pose it...

"What say you'?
 
Re: Residential wiring in NC

So where in the code does it say how much space we need ? would 1/8 of an inch be enough ? Pretty sure we have at least that much unless we are trying to put tention on that wire.
 
Re: Residential wiring in NC

310.15(B)(2) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors in a Raceway or Cable. Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are stacked or bundled longer than 600 mm (24 in.) without maintaining spacing and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a).
Click to expand...
Where I work the inspectors consider wires passing through a series of holes to be "bundled" or at least that spacing has not been maintained.

I also point to one of the exceptions to this rule.

Exception No. 5: Adjustment factors shall not apply to Type AC cable or to Type MC cable without an overall outer jacket under the following conditions:

(a)Each cable has not more than three current-carrying conductors.

(b)The conductors are 12 AWG copper.

(c)Not more than 20 current-carrying conductors are bundled, stacked, or supported on ?bridle rings.?

A 60 percent adjustment factor shall be applied where the current-carrying conductors in these cables that are stacked or bundled longer than 600 mm (24 in.) without maintaining spacing exceeds 20.
Click to expand...
Look at part (c) notice "supported on ?bridle rings.?"

We use these all the time and these are nothing more than metal hooks to support MC cable.

If you install a bridle ring every 4' to 6' feet the cables supported by them usually have space between them in the spans but the NEC seems to consider them bundled.

bundled, stacked, or supported on ?bridle rings.?
Click to expand...
So to save myself aggravation I would not run a group of cables together for more than 24".

[ February 06, 2004, 05:24 PM: Message edited by: iwire ]
 
Re: Residential wiring in NC

If you do not want to drill extra holes just derate and use the proper size conductors.

The code is the code.

Roger
 
Re: Residential wiring in NC

Well all i can say is that in 20 plus years i have always seen them in same hole.Maybe we been lucky that the inspectors don't think this is a violation.I never even questioned it till this post came up.I have no problem with this if we all are doing it.Im just not sure how far apart we need to be before we call it stacking or bundling.
 
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