NM cable

[nizak]

Has there been a change in the 2014 code that deals with the number of NM cables that can be run through bored holes in wood construction?

I am familiar with the deraiting off cables if there is caulk, foam, etc used to seal the hole.

Multiple NM cables run through floor joists without any type of sealant is no longer code compliant?

Up until a month or so ago we were drilling a 2" hole and pulling as many as 12- 15 cables through w/o deraiting, now in 2 seperate municipalities it's a violation.

Has this always been a non Code compliant install?
These are I joists that are on 16" centers with no form of insulation.

Thanks.

 

[infinity]

If the hole does not contain caulk, fire stop or other materials you can put in as many cables as you like according to the NEC without derating. If they're enforcing this differently then it would need to be a local code.

 

[mgookin]

Is the problem with the hole or is the problem with what's passing through the hole?
Can you give us specific language they used?
An I-joist is engineered and should have engineering saying what you can bore.

 

[nizak]

AHJ is saying that the cables are packed too tightly together and that it will cause hot spots.

He did not specifically say they were bundled, just said that heat can build up in each hole they pass through.

I have pulled NM cable this way for 20 years and never had an issue.

 

[infinity]

AHJ is saying that the cables are packed too tightly together and that it will cause hot spots.

He did not specifically say they were bundled, just said that heat can build up in each hole they pass through.

I have pulled NM cable this way for 20 years and never had an issue.

He's making up his own code. The NEC would allow up to 24" to be tightly bundled together without applying derating.

 

[iwire]

He's making up his own code. The NEC would allow up to 24" to be tightly bundled together without applying derating.

'Tightly'? Are you making up code too?

 

[ArcLazerbeam]

He's making up his own code. The NEC would allow up to 24" to be tightly bundled together without applying derating.

Agreed, also

334.80 states,

When more than two NM cables containing two or more current-carrying conductors are installed, without maintaining spacing between the cables through the same opening in wood framing that is to be sealed with thermal insulation, caulk, or sealing foam the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(3)(a) at and the provisions of 310.15(A)(2), Exception, shall not apply.

Just watch where you pull homeruns in exterior walls I guess. Not that this applies to you.

Edit: Taken from 2011, sorry don't have my 14' on me, but I don't believe it changed.

 

[infinity]

'Tightly'? Are you making up code too?

Yup, take 100 cables and tape them together just keep the bundle less than 24".

 

[iwire]

Yup, take 100 cables and tape them together just keep the bundle less than 24".

In my opinion it is up to the AHJ to determine what bundling is.

The NEC does not mention tightly or tape.

or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.)

 

[infinity]

In my opinion it is up to the AHJ to determine what bundling is.

The NEC does not mention tightly or tape.

In my example I'm saying that taping them together IS bundling which does not trigger derating if the length doesn't exceed 24".

 

[Dennis Alwon]

IMO, if you drill a 2 hole in consecutive joists and run cables thru them for more than 24" then that could be construed as bundling. As Bob stated we have no definition of bundling but if you think about it all those nm cables will be laying atop of each other for the entire run thru the joist. Another inspector may not see it this way.

 

[iwire]

In my example I'm saying that taping them together IS bundling which does not trigger derating if the length doesn't exceed 24".

I am saying they could be called bundled even if the tape is 36" apart.

The code does not even use the word bundling in the adjustment factor section, it says 'without maintaining spacing for a continuous length longer than 600 mm (24 in.)'.



In my opinion, for better or worse that leaves a lot of AHJ interpretation.

 

[ArcLazerbeam]

IMO, if you drill a 2 hole in consecutive joists and run cables thru them for more than 24" then that could be construed as bundling. As Bob stated we have no definition of bundling but if you think about it all those nm cables will be laying atop of each other for the entire run thru the joist. Another inspector may not see it this way.

This is how it is enforced in certain areas in my neck of the woods. I'm sure some may disagree but if this isn't considered bundling then I'm not sure what would be

 

[infinity]

I only used the taping together as an example when compared to a hole. The fact is that you can stuff as many NM cables through a hole in the wood as you want as long as there is no fire/draft stopping etc in that hole too. Now run those cables through several holes without spacing that may be a different issue.

 

[James L]

Up until a month or so ago we were drilling a 2" hole and pulling as many as 12- 15 cables through w/o deraiting, now in 2 seperate municipalities it's a violation....

I learned it that way back in the early 90s. But around '97 or so, probably when the '96 code was being adopted, there were wholesale changes in what inspectors around these parts wanted to see.

I remember encountering this bundling head scratcher no later than 1998. Inspectors started flunking with more than 2 wires thru a hole or in a staple.

We used to use what we called "range staples" back when (like 1" wide), and we'd have 7 or 8 small NM cables together in one staple

Second time I got failed, I immediately changed. No more than 2 cables per support.

 

[JFletcher]

If those 12-15 cables run thru multiple joists, I'd consider that bundled. It is not against building code to drill tji's; some can even be cut top to bottom (eta: in the thin section) provided the corners are rounded (ever see what hvac guys do to those things?)

 

[John120/240]

The Smart Joist or I Joist that I am familiar with have perforated knock outs every so often that you smack with your hammer. Run your cables through these holes. Never a question about derating.

 

[JFletcher]

The Smart Joist or I Joist that I am familiar with have perforated knock outs every so often that you smack with your hammer. Run your cables through these holes. Never a question about derating.

Some do, some dont. Always saw the ones that do on commercial jobs, not run across them in resi. Every so often, the holes dont line up; better to drill your own than deal with an unnecessary kick in the pull.

 

[ActionDave]

...Up until a month or so ago we were drilling a 2" hole and pulling as many as 12- 15 cables through w/o deraiting, now in 2 seperate municipalities it's a violation.

Seems like wherever you are is late in getting into the derating game. Inspectors here started trying to solve a problem that never existed a few years after we all got over the Y2K. Those homes you wired with all those romexes stuffed together are doomed. Don't worry about it though, the warrantee has expired everywhere except California and there everybody gets sued at least once a week no matter what.

 

[brantmacga]

I ran into this years ago; AHJ said no more than two wires in a hole. They couldn't show me in the code, then said it was in the building code. They couldn't cite that code for me either but flat out said, we will not pass your inspection. Do it our way or take us to court. So I drilled more holes. I did end up turning them in for charging a local electrical license fee, and the state made them refund every single one for every year they did it. Man that felt nice.


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