Thread: My that lot of cables

Interesting job today.


5 year old home, seller re-location. Would be buyer, is doctor moving into
the area.

This is a single family home. No electrical permit or electrical inspection
is require in my state, when this house was built.

The house general purpose outlets were all feed by 12-2/ground, and
fuse at 20 amps. (this discussion is not about anything else)

I counted, group together into one massive bundle, seventeen 12-2 cable passing through each floor joists.

I check in the NEC 2005 code edition.

Table 310.15(B)(2)(a) Adjustment Factor for More Than Three Current-
Carrying Conductors in a Raceway or Cable.

10 - 20 states an adjustment factor of 50%

Next I took a look at Table 310-16. In the 90 degree columun it is wriitten
that #12 is good for 30 amps. Which the the number I used for derating.

30 A times 50% equal 15 amps.

So I thinking that almost all the 20 amp. breaker will have to be drop
down to 15 amp. breakers.

And all 20 amp. circuits require by the NEC, those cables will have to
be pull loose, and re-route through another set of individual holes.
That way they can keep their 20 amp. breakers.

Well, I have my notes in hand. But before go back and talk to this customer about what I observed.

I am looking for any thoughts and opinions, and perhaps something I
may had over look. (note: no calking and fire foam was observed)

After hearding what you guys have to say, then I will sit down and
write the electrical report.

THANKS.

Similar Threads:

• multiple NM cables entering panel enclosure through one fitting
• Electrical Cables contacting truss plates
• Low voltage cables in disconnect box
• Electrical cables on top of A/C
• Electrical cables contacting each other

Sounds like a mouth full... Any Photos ?

Best

Ron

Ron

Ha! Ha! L.O.L

Your a cracker, what with the, "do you have any photo's".

Originally Posted by Robert S. Mattison

So I thinking that almost all the 20 amp. breaker will have to be drop down to 15 amp. breakers.

And all 20 amp. circuits require by the NEC, those cables will have to
be pull loose, and re-route through another set of individual holes.
That way they can keep their 20 amp. breakers.

Those are your two options, yes.

If the conductors are also routed through the attic (and some may be) or routed up exterior walls (and some may be), then you would need to derate for ambient temperature too, which would reduce the ampacity to maybe as little as less than 10 amps.

You are on the right track, just not enough information to know for sure.

Originally Posted by Robert S. Mattison

Ron

Ha! Ha! L.O.L

Your a cracker, what with the, "do you have any photo's".

Cracker.... yup......I beeees a Cracker You look at my Photo...

Best

Ron

Okay.........there is something in the NEC that allows wires to be grouped together for distance of I believe 24" without derating them. I haven't dug into the code yet but I remember this is in the code. You may be alright or maybe not, but I'll have to dig and find.

Okay....More Than Three Current-Carrying Conductors in a Raceway or Cable

Are there more than 3 current-carrying conductors in a cable? No, not in this case.

Then the code goes on to say.........or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways,


So i read this to say that if the wires are bundles for more than 24" in length, then you have to derate them. If they are just running them through a single hole and then spreading them out, then there is not a violation.


Comments...discussion?

Interesting opinion. I may run that by a local E.C.

But the truth is, these cable are so pack together, you may think that it
is just one cable.

Keep then coming.

Special Thanks to Jerry Peck

I think that the intent of the raceway de-rating is to limit the heat production of the bundle of wires in an enclosed space. If you are passing thru a 2X there would be enough air space for the heat of a 20A circuit to dissipate without the need to de-rate.

Your de-rating math is confusing me. If a 12-2 is de-rated by 50% you would only be allowed 10A. To get the 15A with the 50% de-rating, you would need 10 gauge wire (typical for 30A circuits).

Also, I get the line from electricians that in residential, it is rare for many circuits to be fully loaded at the same time, so your bundle of 17 20A circuits will not ever be fully loaded. Where in commercial electrical the system is engineered for full load. (BTW "full" load is 80% of the wire's rating I.E. a 20A circuit is only rated for a 16A load) In fact I seriously doubt that the house has a 340+ Amp service (not even acknowledging the 240VAC circuits in the house), so not all wires will be making heat. In fact, the ones that are not making heat, will remove heat from the ones that are. Also consider that a piece of 12-2 romex cable has only one current carrying conductor (the hot).

I don't know how big of a hole is drilled in the structural member (and where in the span it is) that these wires are passing thru, but I would be equally concerned about that.

Originally Posted by Wayne Carlisle

So i read this to say that if the wires are bundles for more than 24" in length, then you have to derate them.

Wayne,

Correct, that is what the code requires.

If they are just running them through a single hole and then spreading them out, then there is not a violation.


Comments...discussion?

Well ... kind of ... the code is (has been) addressing and re-addressing this issue as there have been problems caused by this practice - running a bunch of NM cables through a wall stud or top plate (usually the top plate) and then fanning the cables back out.

In fact, over the last several years they have addressed this in the IAEI news with full articles going over this very concern.

Thus, this section was added: (underlining is new to 2008)
- 334.80 Ampacity.
- - The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60°C (140°F) conductor temperature rating. The 90°C (194°F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60°C (140°F) rated conductor. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be determined in accordance with 392.11.
- - Where 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 fire- or draft-stopped using thermal insulation, caulk, or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a) and the provisions of 310.15(A)(2), Exception, shall not apply.
- - Where more than two NM cables containing two or more current-carrying conductors are installed in contact with thermal insulation without maintaining spacing between cables, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).

They started addressing that in 2005, revised it further in 2008.
From the 2005 NEC. (underlining was new to 2005)
- 334.80 Ampacity.
- - The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60°C (140°F) conductor temperature rating. The 90°C (194°F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60°C (140°F) rated conductor. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be determined in accordance with 392.11.
- - Where more than two NM cables containing two or more current-carrying conductors are bundled together and pass through wood framing that is to be fire- or draft-stopped using thermal insulation or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a).

Just a quick note to let you all know that I appreciate all the comments
that have been posted to my thread.

I really enjoy reading them. Keep then coming.

The house in question, is a single story.

This has a full basement with 10 Ft. ceilings.

There 17 bundle cables run through engineer floor joists.

They run in a straight from the electrical panel was directly to the opposite wall.
There no fanning out. A home run cable will only leave
the bundle, when its reach a floor joist bay, were it then run along the
joist until, it reach a location, where it runs up thru the sole plate into
a outlet box.

Originally Posted by Robert S. Mattison

There 17 bundle cables run through engineer floor joists.

That would be 34 conductors.

With a derating factor of 0.40.

Thanks ben jack

I got to take a break from this now.

But I do appreciate, the questions you ask.

Have a got weeken.

If there is no permit required then there is nothing to reference is there? That being said how in Gods name has the insurance companies let this happen. That is what 99% of all codes are for is to protect the insurance company not you and I.

Originally Posted by ben jacks

All the answers you are getting so far are code quotes that do not really define anything you are inspecting physically.

The 24" rule can be ruled out at any joist bay depending on type of joist,

Not really, but is a possibility.

Mostly what you are referring to would relate to boring and notching, not to bundling and lack of maintaining spacing. These are two distinctly different issues.

Originally Posted by ben jacks

Segmenting a sentence out of context can create confusion to the reader. Please understand that there are limitations in bundling interpretation between distance that can impact the total meaning.

You are trying to imply that it affects YOUR meaning?

It does not, however, affect the code's meaning.

There can be 100 cables in the same bundle in a 24" space between open air joisting especially in engineered truss and open joist construction.

Yes you can, and as soon as that length is " ... more than 24" ... " then derating for bundling and lack of maintaining spacing is REQUIRED to be done.

There there is the derating for ambient, which is totally different, and is applied under its own set increments, and is also REQUIRED.

Predicating a statement with an implicating code about a bundle does little without including the physical aspects of the surrounding configuration.

The physical surroundings does not matter, other than if it is thermal insulation, then you need to derate based "Where more than two NM cables containing two or more current-carrying conductors are installed in contact with thermal insulation without maintaining spacing between cables, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a)."

and

"Where more than two NM cables containing two or more current-carrying conductors are bundled together and pass through wood framing that is to be fire- or draft-stopped using thermal insulation or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(2)(a)."

That does not say "If you think it applies.", that says "When this is done, derating shall be done."

Who said there was to be or is any caulking, draft stopping, fire blocking or insulation any where near where the bundled cables are pulled through the engineered joists? The Original Poster inicated this was pre-2004 construction and there was no codes applicable for its construction. He specifically said there was none present.

Hasn't the Original Poster indicated he was looking to 2005 NEC (not 2008) for references to discuss?

Why are facts not submitted by the original poster injected by others?

With 10' ceilings in the basement, seems there is plenty of height to not only close the ceiling but use an assembly to do so. Lets not get ahead of ourselves.

Originally Posted by Robert S. Mattison

I counted, group together into one massive bundle, seventeen 12-2 cable passing through each floor joists.

Originally Posted by H.G. Watson, Sr.

Why are facts not submitted by the original poster injected by others?

The above is what the original poster said, and those are the facts which are, were, the main focus of the discussions.

Thus the discussion revolved around what the original poster said. Along with other side discussions, which we do on this board.

Originally Posted by ben jacks

Run the film anyway you want in your head.

Ben,

I'm running the film the way is was presented by the producer of the film.

Unlike some, I am not editing the film to make it fit what I want, I am commenting on what the film shows.

The producer then comes back in and edits the film, putting in or taking out scenes they want to change for a more clear picture.

Those edited portions of the film are then replayed and reviewed as edited.