310.15(B)(2) add Exception 6.

[hurk27]

This might follow Charlie's statement on the reason's we might wan't to make a proposal.

From another thread by Charlie: A lot of proposals are generated by individuals who are trying to get relief from a particular inspector or group of inspectors.

So very true. But sometimes there are some unnecessary codes that conflict with other building codes that can make an installation more complicated than it needs to be.
And this one it has been a thorn sometimes with allot of inspectors and contractors. as we have seen post here already.


1.) NEC Section/Paragraph: 310.15(B)(2) add Exception 6.


2.) Proposal Recommends: [new text]
(Exception No. 6: derating factors shall not apply to cables ran in bored holes, or cut notches in floor joist or interior walls in residential dwellings where it meets

(a) Where these cables are run in bored holes in a wall, Floor, or ceiling space,where the ambient temperature will not exceed 40 deg. C. in normal use.
(b) Where these cables are run in any floor, wall or ceiling space with a high ambient temperature, The derating require in 310.15(B)(2) shall be followed.

4.) Substantiation: Where there is cables ran in bored holes in joist with spacing between each joist, the maximum load on these cables, will most likely never be used. the temperature of these cables would never run beyond the safely rated temperature of the cable. As the code is now it requires multiple holes to be bored in floor joist to accommodate the circuit runs and most building regulations limit the amount of these holes that can be safely bored into floor joist.

 

[charlie]

Re: 310.15(B)(2) add Exception 6.

I like the concept and have made some suggested changes. We are ready for more comments and tweaking.

1.) NEC Section/Paragraph: 310.15(B)(2) add Exception 6.

2.) Proposal Recommends: [new text]

Exception No. 6: derating factors shall not apply to cables ran in bored holes, or cut notches in joists or interior walls in dwellings under the following conditions:

(1) Where these cables are run in bored holes in a wall, floor, or ceiling space, and where the ambient temperature will not exceed 30?C in normal use.

(2) Not more than 10 current carrying conductors are included in the bundle and are not larger that No. 12 Cu. or No. 10 Al.

4.) Substantiation: Where there are cables run in bored holes in joists with spacing between each joist, the maximum load on these cables, will most likely never be used because of the load profiles in dwelling units. The temperature rise of these cables is minimal under these conditions. By limiting this exception to 15 and 20 ampere circuits, the range, dryer, electric furnace, etc. are excluded and the likelihood of more than one or two heavily loaded circuits are eliminated.

The code now requires multiple holes to be bored in floor joists to accommodate the runs and building regulations limit the amount of these holes that can be safely bored into floor joist. This places an undue burden on the electrician to find exit routing from panelboards. This proposal will provide some relief from the stringent requirements.

 

[websparky]

Re: 310.15(B)(2) add Exception 6.

Wayne,

I'm not sure I would agree with the need for a change. Here is why:

NM is 60C
NM 12AWG = 30A @ 90C * 70% = 21A


9 current carrying = 70% Derating
That means you can install
9 - 12/2 NM bundled = 21A
or
4 - 12/3 NM bundled =21A

If you are installing more than this in one hole or bunched together in the "stackers" you are not installing them properly in the first place!

I get to see more than 1400 residential installs per year. On occasion I find too many NM's "bundled" or "stacked". Usually it is the result of a new installer and an unusually difficult lay-out. The electricians up here are pretty good at planning a job and pretty creative with their lay-outs. So far only 2 red tags for overloading the "stackers". Not bad!

 

[roger]

Re: 310.15(B)(2) add Exception 6.

Hello Dave, actually 9 12/2 NM cables would be 18 current carrying conductors.

Editted for spelling (carring verses carrying )

Roger

[ November 25, 2004, 01:39 PM: Message edited by: roger ]

 

[hurk27]

Re: 310.15(B)(2) add Exception 6.

Charlie I was just thinking: If the service is a 100 amp or even a 200 amp it would be very hard to have enough current on these current carrying conductors with out over loading the service and tripping the main wouldn't it? 10 20 amp circuits would trip a 100 amp and would be very close to tripping a 200 if there were any other loads. so if this is true then why should there be any limit as the service main would keep these circuits limited wouldn't it?

Edited because I just relized that were talking about 120 volt circuits and the service could have 10 20 amp circuits on each leg and it would still be only 100 amps. Oh Dah!

[ November 27, 2004, 01:09 AM: Message edited by: hurk27 ]

 

[websparky]

Re: 310.15(B)(2) add Exception 6.

Hello Roger,

Humm.......I didn't think we had to count 'em?

(4) Neutral Conductor.
(a) A neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted when applying the provisions of 310.15(B)(2)(a).

 

[hurk27]

Re: 310.15(B)(2) add Exception 6.

Dave that would be true for the 12/3's but the 12/2's the neutral would have just as much current on them as the hot. Look at your original post.

 

[charlie]

Re: 310.15(B)(2) add Exception 6.

Gentlemen, the reason that I believe this proposal has merit is the way residential circuits are loaded. If I bundled all the 15 and 20 ampere circuits in my home together, I would have a large bundle and not use but three or four circuits at a time. I get up and will use the bathroom circuit and kitchen circuit (gotta have coffee), I'll have a few lights on and then the garage door opener. The water heater circuit is #10 so it would not be included.

Now go through each part of your day in the same manner. The heavy load will be at dinner (trust me). The SA circuits will be used along with the kitchen and eating area lights. Lets do the laundry (can't count the 30A dryer circuit or the 30A WH circuit) and run the dishwasher. We are hitting 2 SA, 1 DW, 1 washer, and misc. lights. Where is the overloaded bundle?

I wonder if this needs to be included in the substantiation?

 

[websparky]

Re: 310.15(B)(2) add Exception 6.

Wayne,

OK.. even if we count them that way, I still am not sure a change is needed.

If as you and Charlie are in agreement about the need, please also consider the effects of the cables when run in wall cavities or ceiling joist spaces that contain insulation. Their normal heat dissipation ability is considerably reduced.

Maybe something like this should be added:

394.12 Uses Not Permitted.(5) Hollow spaces of walls, ceilings, and attics where such spaces are insulated by loose, rolled, or foamed-in-place insulating material that envelops the conductors.

[ November 27, 2004, 12:18 PM: Message edited by: websparky ]

 

[hurk27]

Re: 310.15(B)(2) add Exception 6.

Dave that was covered in the exception already look at the first requirement it has to meet

(1)Where these cables are run in bored holes in a wall, floor, or ceiling space, and where the ambient temperature will not exceed 30?C in normal use.

I'm not an engineer and thought 40oC would be sufficient but Charlie who would know dropped it to 30oC

Ok Charlie how did you make that degree mark? It's not on my keyboard

 

[physis]

Re: 310.15(B)(2) add Exception 6.

Wayne, I just saved it to a notepad file and now I can copy it from there. ?

180?

I think I'll start collecting characters like this.

 

[hurk27]

Re: 310.15(B)(2) add Exception 6.

You know Sam I didn't even noticed that when I copied it from the other post that it also copied the degree character too. 30?C Cool Thank's

 

[charlie]

Re: 310.15(B)(2) add Exception 6.

I'll give you a list of some that I like to use. Hold down the ALT key while you type in the whole number on you key pad.

0169 ? Copyright
0174 ? Registered
0176 ? Degree
0177 ? Plus or Minus
0178 ? Superscript 2
0179 ? Superscript 3
0185 ? Superscript 1
0188 ? 1/4
0189 ? 1/2
0190 ? 3/4
0216 ? Phase mark

Use your notepad and you can see what other symbols can be made.

 

[iwire]

Re: 310.15(B)(2) add Exception 6.

I can't make it work

 

[hurk27]

Re: 310.15(B)(2) add Exception 6.

This is so cool Charlie I had no Idea.

ؾ???oo+_???p&???D?????

 

[hurk27]

Re: 310.15(B)(2) add Exception 6.

Bob hold down your Alt button then type the 074 then let go of the Alt button and it appears. also if your using you number key pad make sure numbers lock is on.

 

[iwire]

Re: 310.15(B)(2) add Exception 6.

I will give it another try.

Nope nothing from the numbers at the top or from the keypad.

Maybe a setting has to be changed?

 

[hurk27]

Re: 310.15(B)(2) add Exception 6.

What kind of computer is it not an Apple is it?
??????{宯????????~?|}?????????Xh?-_GB??O_?jJ+_x+++o++?A_?}??

Mine is a PC and it works all to good. Now I have somthing else to check out.

 

[roger]

Re: 310.15(B)(2) add Exception 6.

}o{0?0-@?N0-{棺_?

Thats neat

Roger

 

[iwire]

Re: 310.15(B)(2) add Exception 6.

Originally posted by hurk27:
What kind of computer is it not an Apple is it?

No it is an IBM type....do we still describe it that way or do we simply say a Windows machine?