I am wiring a new house that is using I-joists'. have wired other houses with these. and usually will drill a 2 1/2" or 3" hole towards the top about 3" down and run most of my wires through that hole.. My question is, how many wires are allowed through that hole? and do you get into a derating problem? my inspector says it is ok. I have about 20 wires through it, and most are #12... what do you guys think?

Hi,
Watch out...there are strict rules about WHERE you can drill in manufactured beams!

For the most part do not get out of dead center.

As for the wires...20 is too many for one hole no mater what the cable is feeding!

Check 334.80

310.15(B)(2)(a) 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). (the preceeding was copied from another post on the subject)

-regards

Mustang


[This message has been edited by mustangelectric (edited 12-07-2004).]

I assume that the wiring method is Type NM cable. Installing 20 No. 12awg cables through a 2-1/2" hole is OK, provided that they are not bundled (secured together) for a distance in excess of 24". See 310.15(B)(2)Exception No. 3.

Where did you get the definition of bundling as "secured together"?
It has been explained by Mike Holt, and etc. that multiple cables installed in bored holes are bundled. Don't you think that the bored holes every 16 or 24 inches secure the cables together?

Bundled.

Cables or conductors that are physically tied, wrapped, taped or otherwise periodically bound together.

thanks for your input guys. didnt want to get all roughed in and have to tear everything back out. wayne

So, Joe, are you saying that NM cables installed in bored holes are not bundled, and therefore we can install as many as we want in a large hole?
I don't see a definition in Article 100, is that from the dictionary?

Mustangelelctric & all

Go to the following to see what BCI recommends for their product.
http://www.aecinfo.com/1/resourcefile/00/22/89/bcwspe22.htm

Steve

If the bored hole is through a piece of wood in excess of 24 inches, I would say the cables need derating just as through a raceway. If it is a series of holes through 1/4" wood members every 16-24 inches I don't believe derating is needed. If the cables are stuffed tightly where they pass through the holes I think the issue would be physical damage to the cables rather than derating.

SKI-Thanks for that reference. Now we know!

-regards

Greg

When you are talking about derating and bundled cables, neatness is your enemy. You really want them to be very disorganized between holes. You want the "inside" cable in hole "A" to be outside in hole "B". I really don't start thinking about derating unless I see a very pretty bundle with carefully aligned cable bundles. The cables in the middle are cooking. If you fan them out between holes they can breathe.
I have seen inspectors make the same demand in large panels that were a thing of beauty but they had big bundles of THHN going more than 24". The EC almost cried when he had to cut those tywraps and spread the wires out, "messing up" that panel.

The I joists I've seen have a prepunched hole every 18 inches or so. Kinda like a KO, hit it with a hammer and out pops the wooden slug.

My experience about the KO's is that I have never seen a framer line up the TGI's so that the KO's could be used in a neat and workmanship like manner. Usually staggered (because of length cutting at the lumber yards for delivery), or some tipped upside down in relation to the others. Usually end up drilling anyway. Here in Wisconsin most heating contractors prefer wiring that is installed first to be closer to the bottom of the TGI. For a smaller hole of 2", I think the books that come attached to some of the TGI's usually say within 1/2 inch of bottom support ridge (or whatever they are called). Holes must be twice the diameter appart for most requirements that I have read. On bundling, here in Wisconsin there is an adoption to the code with exclusions like AFCI for bedrooms, and for bundling of romex. Check your state codes?

Earl:


Yes and the Definition of "Bundled" comes from Article 520, and not from 100.

Good canidate for 2008 proposal.

Added Emotion Graphic



[This message has been edited by Joe Tedesco (edited 12-24-2004).]

Romy: welcome to ECN fourm here ,

I am in wisconsin also and i am not far from your area in fact about 15 min will ring the bell to ya.

anyway yes Wisconsin will adopt new code but for AFCI it will be enfored but i havent heard the final word yet, but they should inform me anytime soon about the state code along with few additional change along for new code cycle.


anyway for the wooden I beam type that is very tricky part i did see and some have prepunched holes but majorty of my time i dont like to use prepunched hole due what you and few other guys described and it show poor workmanship and waste extra unneed materals and time but i know Ryan [ the electrical/ building inspector ] do show up here from time to time and i think he have a link somewhere we did look it back sometime ago related with the wooden I beams


merci, marc

I wish I had the instructions for the I joists. I'd guess those KOs are placed in the joists where the manufacturer wants. Seems to me that thats more important than neat and workman like?

Walrus,

The concept is great. Problem is the TGI floor joist come in longer lengths to the lumber yard than most customers need. They at the lumber yard then cut them for size with a chain saw type tool. This can put the holes back and forth in a wire run as much as eight inches or so. Add to that every time one is used in a different side up to the floor, then the vertical alignment doesn't line up with the run either. I have seen some installations where they were used anyway, and it didn't look good. Besides the look, think about making the 3rd, 4th, and 5th pulls through these staggard holes. Like pulling romex with someone on the other end holding it back for every turn. These holes are generally close to the center of the joist and the heating men have a hard time putting their six inch ducts perpendicular to these cable runs. Sometimes pulling a little slack from both dirrections works for them, but with these misaligned holes there is no pulling of slack without a come along.

As for the Wisconsin code being adopted and enforced, it ususally takes about one year for all the suits to make up their minds on all the details and send out their com. 16 State adoption to the NEC. In the time they are deciding, we continue to go by the previous accepted code. The rumors that I have heard have it that the suits have still not come to terms with the Arc Fault Circuit Interupters, especially with all the new reports of them not working as they should.

Joe
I am just wondering if the 520.2 definition of bundling can be used as an enforcement type of definition elsewhere in the NEC, as this definition is not in Art 100?

Like you, I see a 2008 NEC proposal for this .

Pierre

Bundled.
Cables or conductors that are physically tied, wrapped, taped or otherwise periodically bound together.....


Otherwise periodically bound together???? Couldn't a inspector consider joists as periodically bound?

My standard is if they get fanned out between points where they are together.
The point is you can't have 24 continuous inches without a chance to breathe. The more air the better.

Can we equate this large bored hole to a cable tray? Are there any rules on installing cables in cable tray? Would they then apply?
I see in 392.11(A) that multiple cables are allowed to be installed in open cable trays without derating of the conductors, so long as the individual cables do not require derating due to more than three current carrying conductors in one cable.
Using these rules for bored holes in basements is a stretch, I know. But maybe somebody's proposal can borrow some of the verbiage.

I'll bet if bundling were required the joists wouldn't satisfy bundling.

Can you Have it both ways?

Can any one of the people who insist that multiple runs of romex thru drilled holes in DWELLINGS needs to be derated show us any event that has actually contributed to a single house fire, unless a branch circuit itself was improperly overloaded?

I don't beleive that code requires derating because multiple cables pass through a joist or joists.

I would ask an inspector, or anybody else, to show me in code.

By Gfretwell:

"I really don't start thinking about derating unless I see a very pretty bundle with carefully aligned cable bundles. The cables in the middle are cooking. If you fan them out between holes they can breathe."

I wish I could claim to be the guy who came to this realization but I'm only repeating something that I heard from smarter people.

If you're talking about a residence. And you have only 12 and 14 AWG NM (no ranges heaters and such). Think about the load you're likely to find throughout the entire building at any one time. Even if you bundle all those circuits, I don't think in the vast majority of cases you'll have enough current to cause enough heating that you would need to derate.

Edit: fixed spelling

[This message has been edited by Physis (edited 12-29-2004).]