The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Sprinklered equipment 26-008
by bigpapa
12/02/16 04:24 PM
On Delay Relay with Auto Reset
by Potseal
12/01/16 09:59 AM
Wow, that was close!
by jraef
11/28/16 07:06 PM
Earthquake in New Zeeland
by RODALCO
11/27/16 11:25 PM
Calling all Non-US members!! (Non-US only)
by Tjia1981
11/27/16 06:33 AM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
HotLine1 9
Trumpy 8
Texas_Ranger 8
sparkyinak 7
Who's Online
0 registered (), 255 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#77205 - 05/14/01 04:22 AM Wires per hole??
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
an oldie, but goodie....

how many wires can i put in a hole?

assume rx or mc thru wood joists here....



Top
2014 / 2011 NEC & Related Books and Study Guides
#77206 - 05/14/01 05:50 AM Re: Wires per hole??
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
As many as will fit in the hole. Remember that the hole must comply with 300-4 and must not destroy the structural strength of the framing member. This assumes that the cables will NOT be tightly bundled between framing members.
Don(resqcapt19)
_________________________
Don(resqcapt19)

Top
#77207 - 05/14/01 08:53 AM Re: Wires per hole??
wayne Offline
Member

Registered: 04/04/01
Posts: 55
Loc: NC
Sparky,
That is a good One.

That would Depend On the size of the hole.We would still consider art 300-4 in application of this method.

Wayne

Top
#77208 - 05/14/01 09:30 AM Re: Wires per hole??
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
I've mentioned before in another thread (there ought to be a law) that I'd like to see a requirement for bored-hole fill similar to pipe fill. I use it as a rule of thumb when dealing with larger cable, (2" for 4/0 SE. 1-1/4" for #2 SE, etc.)

As far as #14 and #12 NM Cable, I go no less than 3/4" , usually 1".
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

Top
#77209 - 05/14/01 12:39 PM Re: Wires per hole??
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
Virgil;
yes you did, and it's worthy of a thread's consideration.

to add to the Q,
what would qualify as 'bundled'


Top
#77210 - 05/14/01 02:23 PM Re: Wires per hole??
Anonymous
Unregistered


A bored hole through a 2"X4" seems to have a lot in common with a nipple especially if the wall is insulated too.

Do you mean that some people don't make a separate hole for each cable on minimum one-diameter spacings?

Top
#77211 - 05/14/01 02:37 PM Re: Wires per hole??
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
 Quote:
Do you mean that some people don't make a separate hole for each cable on minimum one-diameter spacings?


If I did that I'd be making $3 an hour on bid jobs... but for cost-plus, that's OK!

Please don't tell me it's code to do so...is it? It'd make swiss cheese out of the homes I've wired. One hole in the center of the joist/stud/plate makes for less structural degradation.

Bundled cable derating is one of the most ignored codes around here to this day... heck I'm guilty of it I suppose...
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

Top
#77212 - 05/14/01 03:10 PM Re: Wires per hole??
Anonymous
Unregistered


 Quote:
Please don't tell me it's code to do so...is it?


Of course it is legal to do so...


I can't speak to structural degradation, but I can't imagine how Swiss cheese is worse than a big whole. My gut feeling is that a bunch of half inch holes a half inch apart cause less weakening than a single large hole.

I've pulled NM out of joists where the holes were sized and shaped almost exactly to the oval shape of the cable.

Of course, 12-3-G fills a round hole nicely.

Let's just say that I lean toward Swiss cheese as the preferable way. I think so long as I'm leaving 60% there, it's structurally safe.
If you are making a single hole up to 1.5", I wouldn't object, especially if you are restoring it with steel.

Perhaps you need a faster drill or a sharper bit.

It's easier to trace wires through Swiss cheese than in a bundle, but a little harder to protect with plates.

No derating in Swiss cheese...

Top
#77213 - 05/14/01 03:56 PM Re: Wires per hole??
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
Myself,
There are probably few people outside of our trade that appreciate our's as having any asthetic value, but i just like a neat job.

if i do a complete building, i like to wire for expansion. So when it comes to wood i usually arrange via chalkline 3 to 4 1 1/2" or 2" runs back to the panel, possibly more closer to the panel. First i ask the carpenters, they are responsible for load bearing, etc. The time i take to do this pays off. I have found a self-feed and right angle works best, having all holes at an angle tends to work the wires thru hard.

All the runs are pulled easily, they occupy on average 1/3 to maybe 1/2 of the hole diameter, always room for that future sparky.

All runs starting from the panel fan out neatly, which looks good as an end result.


Top
#77214 - 05/14/01 04:07 PM Re: Wires per hole??
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
I believe the derating factor for 1" holes dead center of the framing member to have about a 4% decrease in structural integrity. 1/2" holes would be 3%. If they are not dead center, then up to 30% derating of the load carrying ability of the member must be assumed. I was told this by a P.E. I worked for, so I can't back up its accuracy. So it's kinda moot.

I guess the important thing is to have them dead center.

I don't put more than three cables in one hole under any circumstances, just a rule of thumb.

 Quote:
$3 an hour

I should mention that I tend to "exaggerate for clarity" if that makes any sense. In today's sensationalized world, sometimes it's hard to get a point across without going to the extreme!

[This message has been edited by sparky66wv (edited 05-14-2001).]
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

Top



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals