Bunching Romex

[Lawrence Thomas]

I remember that in one of my electrical training classes, the instructor told us that not more than four strands of romex should be bunched through any feed through because romex still needs to dissipate heat. I was in a 6 year old house today and in the basement utility room (very near the sub-panel) there were several instances of 6 or 7 strands passing together through one opening in the floor joists. Is this just bad practice or is it a defect that should be made a review item?

[David McGuire]

The thing is, when you have that many bundled together you have to derate them, example would be if there were 7 to 9 20 amp romex conductors for a distance of 24" that didn't split off you would need to derate them from 20 amp down to 17.5 amps.

But around here it is not uncommon to see 7, 8 or even 9 bundled together. As is in your case and most cases, the closer you are to the service panel, the more cables in a bundle.

Back to your picture, was the contractor consistent with the cutting of his holes through the engineered joists. Rarely do I see it done properly.

[Jerry Peck]

The thing is, when you have that many bundled together you have to derate them, example would be if there were 7 to 9 20 amp romex conductors for a distance of 24" that didn't split off you would need to derate them from 20 amp down to 17.5 amps.

9 two-conductor cables means 18 current carrying conductors, and 10-20 current carrying conductors is derated to 50%.

12 NMB is derated from 30 amps and 14 NMB is derated from 20 amps, so, presuming no derating for ambient temperature (i.e., not in an attic for example), 12 NMB would have a 15 amp rating (not suitable for anything greater than a 15 amp breaker) and 14 NMB would have a 10 amp rating (not suitable for anything at all basically).

Now, if *any portion* of the any one of those circuits goes through an attic, than that entire circuit also needs to be derated for ambient temperature, and if we presume a typical 125 degree attic, the derate rating is further derated to 76%, which would make 12 NMB derated to 11.6 amps (not suitable for anything at all basically), and 14 NMB derated to 7.6 amps (making it a wasted used of copper not suitable for anything).

And, if the attic temperature is higher than 131 degree (and up to 140 degrees) the ambient derating factor is 0.71 instead of 0.76, and if the attic temperatures reach 141 degrees to 158 degrees, the derating factor is 0.58.

What really kills bundling and lack of maintaining space is having to derate for ambient *and* more than 3 conductors, derating for more than 3 conductors is bad enough.

[Bill Kriegh]

In order for cables to be considered bundled they have to be in contact with each other for a minimum of 24 inches. And, as soon as the cables don't touch, the 24 inch minimum starts over. So, as long as cables don't touch continuously for over 24 inches they aren't bundled.

People fuss about this continuously, but the language in the NEC is very clear. And, there is seldom a bundle of NM-B where the cables are in intimate contact for 24 inches unless strapped with wire ties.

Cables running horizontally through framing usually don't have bundling issues, at least technically, because if you look closely the cables don't maintain contact. And, if some is found that does touch it takes a fairly light pressure to move a cable enough to make a space between it and a cable that touches.

If you look closely and objectively at both pictures there may be a couple of cables that would be considered bundled. But, even then it could be the angle the picture was taken from.

Close proximity doesn't count - the cables HAVE TO TOUCH CONTINUOUSLY for the 24 inches.

NEC 310 (B) (3) 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 installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(3)(a).

The rules change immediately if the bundle of cables goes through an opening required to be fire stopped.

[Jerry Peck]

In order for cables to be considered bundled they have to be in contact with each other for a minimum of 24 inches. And, as soon as the cables don't touch, the 24 inch minimum starts over. So, as long as cables don't touch continuously for over 24 inches they aren't bundled.


Incorrect, cables like those in the photo are considered bundled and/or lack of maintaining spacing (take your pick, both are requirements). I've talked with engineers at the cable manufacturers, UL, and a several others, there are two trains of thought on "maintaining spacing": 1) start out at a box and fitting and "maintain" that spacing spacing; 2) maintain at least 1/4" separation between cables, and "maintain" that spacing all the way. Otherwise derating applies.


People fuss about this continuously, but the language in the NEC is very clear. And, there is seldom a bundle of NM-B where the cables are in intimate contact for 24 inches unless strapped with wire ties.

The wording in the NEC is very clear, and it very clearly does 'not' say what you said it does, it very clearly simply says:
- (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 installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a). Each current-carrying conductor of a paralleled set of conductors shall be counted as a current-carrying conductor.

That clearly does not say 'not touching'.


Cables running horizontally through framing usually don't have bundling issues, at least technically, because if you look closely the cables don't maintain contact. And, if some is found that does touch it takes a fairly light pressure to move a cable enough to make a space between it and a cable that touches.

The IAEI and its articles disagree with you. A few years ago they ran tests on just that and had a large article stating that, even though that does not violate the wording of the code, that practice does lead to building up a lot of heat at those areas and fires may have been started by that practice.


Close proximity doesn't count - the cables HAVE TO TOUCH CONTINUOUSLY for the 24 inches.

Very clearly incorrect - read the code, do not add your own wording and thoughts to it ... *the code* *does not say what you are saying it says* ... very clearly so.

There are many electricians who down play bundling and derating, yet the NEC "clearly" continues to include it as it is "clearly" an important factor.

[Jim Port]

Jerry, I can certainly see BKs interpretation as the cables are parallel but the closest contact is only where they pass through a non-firestopped framing member. In the pic posted that area is a 1/2" thick plywood web. Well less than the 24" mentioned in the code. Also the "maintain spacing" is not defined as a distinct measurement. The 1/4" you posted about is the first time I have seen an actual dimension, but it is not in the code.

You mentioned start out at a fitting an maintain that spacing. A typically NM connector has the cables in intimate contact, although a small distance where the clamping takes place.

[Jerry Peck]

Jerry, I can certainly see BKs interpretation as the cables are parallel but the closest contact is only where they pass through a non-firestopped framing member. In the pic posted that area is a 1/2" thick plywood web. Well less than the 24" mentioned in the code.

That is the place where the cables are wedged together, yes, but not the point where lack of maintaining spacing occurs.


Also the "maintain spacing" is not defined as a distinct measurement. The 1/4" you posted about is the first time I have seen an actual dimension, but it is not in the code.

And, as I pointed out previously, Bill's "as soon as the cables don't touch" is not in the code either.


You mentioned start out at a fitting an maintain that spacing. A typically NM connector has the cables in intimate contact,

Not where one NM cable is in one NM cable clamp, which is what the spacing is based on for those whom I have talked with and who brought that up - there is a definite space between the NM cables where they enter the plastic box with the built-in clamps, there is also a definite space between the knock-outs/threaded hubs in metal/plastic boxes too, and that is 'the spacing' which the code could be referring to which needs to be maintained.

The code is not "clear" on "maintaining spacing", and Bill said it was "clear" in his post, that is why I referenced the code as 'not' being "clear" as it "clearly" is not "clear".

There are several types of NM cable standoffs which address and solve this problem.

When I have a question like this (regarding what is "maintaining spacing") I go to the sources to find out what they say, and the engineers for Southwire (you know, the manufacturers of RomexTM), and to UL, and to NFPA, and find out what they say.

That was probably about 10-15 or so years ago, and the engineers at Southwire said "No one has ever asked that question before" and they called a few of their other engineer's and at first said "I suppose that 1/4" would be maintaining spacing as the cables do need to ventilate and be able to dissipate the heat which may build up", and then one of the engineers said that could be read "as meaning the spacing between the connectors in the boxes is the spacing which needs to be maintained".

There are many electrician who simply feel that maintaining spacing is 'no big deal', but the NEC must consider it as still being a big enough deal as they keep that section in the code. When, or should I say "if" because I doubt it will happen ... when the NEC drops the requirement for maintaining spacing or drops the requirement to derate for not maintaining spacing, then I will follow them and quit "going there".

In the meantime, though, it still is a code requirement to derate if spacing is not maintained - that cannot be argued. The separation distance required is the only thing which can be argued - and it does get argued about now and then. :)

Added with edit: I forgot to add that the engineers at Southwire 'passed through' this when discussing what "maintaining spacing" was: one of them suggested that the width of a finger would suffice, then the discussion went to who's finger as fingers are different widths, another engineer solved that by saying that if the NM cables were spaced apart from other cables by the width of that cable, thus the larger the cable the more current and heat and the greater the spacing - all seemed to agree that was reasonable ... but unrealistic to expect ... thus they ended up at the 'spacing of the connectors to the boxes' and at ' 1/4" ' (which are definitely not the same, but that 1/4" was the closest spacing discussed.

[Bill Kriegh]

That is the place where the cables are wedged together, yes, but not the point where lack of maintaining spacing occurs.

Jerry, you gotta quit putting stuff in the book that isn't there

And, as I pointed out previously, Bill's "as soon as the cables don't touch" is not in the code either. Yes it is. In contact continuously for more than 24 inches means just that. If the cables are in contact for 23 7/8 inches, then move apart, then touch again for 23 7/8 inches, according to the wording in the NEC they aren't bundled. Doesn't matter what the intent is - the wording says what is or isn't OK and it says not bundled unless touching for more than 24 continuous inches.



Not where one NM cable is in one NM cable clamp, which is what the spacing is based on for those whom I have talked with and who brought that up - there is a definite space between the NM cables where they enter the plastic box with the built-in clamps, there is also a definite space between the knock-outs/threaded hubs in metal/plastic boxes too, and that is 'the spacing' which the code could be referring to which needs to be maintained. Could be, but doesn't. All the NEC says is "some" space must be maintained, and there's no rule it must be consistent, or what the minimum is.

The code is not "clear" on "maintaining spacing", and Bill said it was "clear" in his post, that is why I referenced the code as 'not' being "clear" as it "clearly" is not "clear". Very clear, they can't touch for more than 24 continuous inches. Spacing can be "piece of paper" wide or several feet. It is NOT defined

There are several types of NM cable standoffs which address and solve this problem. Most "stacker staples do not maintain anywhere near the distance between cables that holes in boxes have, and, incidentally, these holes and/or fittings can have 2 cables. A group of cables run vertically in a wall in one of these approved "stackers" winds up looking much like the runs of cable in the OPs pictures because the cables aren't perfectly straight. The spacing between the different "layers" in these stackers looks to be about 3/32 or so, hardly a 1/4" or a "finger", and at 2 cables per layer(4 of them) with no divider can touch in the stacker. Neither spacing is anywhere close to the spacing of the holes in a nail on plastic box or the holes in a 4 square metal box. Remember, these things are UL approved for the purpose.

When I have a question like this (regarding what is "maintaining spacing") I go to the sources to find out what they say, and the engineers for Southwire (you know, the manufacturers of RomexTM), and to UL, and to NFPA, and find out what they say. I know what the engineers say. What we're talking about here is what's in writing and has the force of law when applying the NEC to an installation

That was probably about 10-15 or so years ago, and the engineers at Southwire said "No one has ever asked that question before" and they called a few of their other engineer's and at first said "I suppose that 1/4" would be maintaining spacing as the cables do need to ventilate and be able to dissipate the heat which may build up", and then one of the engineers said that could be read "as meaning the spacing between the connectors in the boxes is the spacing which needs to be maintained".

There are many electrician who simply feel that maintaining spacing is 'no big deal', but the NEC must consider it as still being a big enough deal as they keep that section in the code. When, or should I say "if" because I doubt it will happen ... when the NEC drops the requirement for maintaining spacing or drops the requirement to derate for not maintaining spacing, then I will follow them and quit "going there".

In the meantime, though, it still is a code requirement to derate if spacing is not maintained - that cannot be argued. The separation distance required is the only thing which can be argued - and it does get argued about now and then. :)

Added with edit: I forgot to add that the engineers at Southwire 'passed through' this when discussing what "maintaining spacing" was: one of them suggested that the width of a finger would suffice, then the discussion went to who's finger as fingers are different widths, another engineer solved that by saying that if the NM cables were spaced apart from other cables by the width of that cable, thus the larger the cable the more current and heat and the greater the spacing - all seemed to agree that was reasonable ... but unrealistic to expect ... thus they ended up at the 'spacing of the connectors to the boxes' and at ' 1/4" ' (which are definitely not the same, but that 1/4" was the closest spacing discussed.

So, no need to go there. Put it in the NEC, put a label on the wire. Basically, do something about it besides say "this is what we think" and make it a rule.

What we have here is a Watsonism - some CMP or some engineer said something to somebody somewhere so I know what the intent is and you don't so a I'll tell you. Sorry:rolleyes: Doesn't matter. It's not in the NEC what the spacing needs to be, and it isn't on cable packaging or instructions either.

Yes, a properly installed installation dictates there needs to be spacing between cables. But, with the language in the book, you'd loose in court if you said either of the OPs pics showed bundling based on the written material available. Maybe someday we'll chat about how I know that for a fact.

[Jerry Peck]

Bill ... *I* need to stop putting words in the book??;

*You* need to quit putting words in the book.

*No where* im the book does it say the cables only need to not touch.

Your post sounded like Watson trying to defend some of his posts.

[Jerry Peck]

Yes, a properly installed installation dictates there needs to be spacing between cables. But, with the language in the book, you'd loose in court if you said either of the OPs pics showed bundling based on the written material available. Maybe someday we'll chat about how I know that for a fact.


I replied using my smart phone for my previous post - those small screens are just not made for this stuff, anyway, after re-reading your post on my computer ...

"you'd loose in court if you said either of the OPs pics showed bundling based on the written material available."

The other party would not win either ... for the same reason. Which means if they sued me, they would not win. :p

And there is no reason for me to sue them, if they want to overcome my statement they would be suing me. :p :p

[Jim Port]

Asking a few people sitting around a table about their thoughts about spacing hardly seems like an official way to determine the defintion of maintaining spacing. Especially when variables like KO spacing or about a finger width are mentioned. I doubt the any NRTL would use such a variable condition in a valid test to determine negative effects due to heating etc. As I stated above many UL listed NM connectors can accept two cables and this places the cables in intimate contact. This contrasts with some of the roundtable "data" that was posted above. Suppose that a 4 square box is used but only the two outside KOs are used on one side. Does this now mean that the cables need to remain 2" apart for their entire distance? If they do not you have not maintained the spacing. Would adding a cable to the middle KO violate the spacing? Single gang plastic boxes can have two flat cables enter through the same KO tab. What is the spacing now? Certainly less than 1/4", more like 1/16".

[Jerry Peck]

As I stated above many UL listed NM connectors can accept two cables and this places the cables in intimate contact.

And, even by your posts and Bill's posts, if that "intimate contact" was maintained for more than 24" derating would be required.

So, as I posted above, there can be *no* argument that derating is a *code requirement* when bundled or lack of maintaining spacing. The *only thing* which can be argued is *what exactly is that spacing*.

I also added that has been argued here before, and, apparently, still is being argued here ... as neither you nor Bill have anything which proves your side of the argument any more than I do which proves my side of the argument ... so ... let's keep arguing ... only let's argue about what the code *does say* - *that derating **is** required* for certain conditions ... ;)

Are you and Bill saying that derating *is not* required for certain conditions? (If you are, then I win that one hands down and in black and white code wording. :p )

[Jim Port]

I would not say that derating is not necessary, but that the "maintained spacing" is entirely ambiguous. I don't necessarily believe that parallel cabling automatically means that they are bundled. I also read the code that it is only an issue if the 24" is in continous contact. I forget who posted about the 23 7/8" of contact with a gap and 23 7/8 would be compliant but the wording can certainly be seen to support that viewpoint. This is reinforced by the similar restriction about derating in nipples only applying if the nipple is greater than 24".

[Jerry Peck]

I also read the code that it is only an issue if the 24" is in continuous contact.

The code does not reference in continuous contact in any way. The code only references "without maintaining spacing for a continuous length" but does not define what "maintaining spacing" is.

Take your typical "bundle" where the cables are "bundled" with tie-wraps even spaced at every 6" to 12" - I am sure that you would call that a "bundle", I suspect that anyone would call that a "bundle". Yet the cables may very well not be "in continuous contact" all the way along that "bundle". But surely the cables are not "maintaining spacing for a continuous length" for that 24".

If you look at (b) in the adjustment factors you will get a sense on where the spacing to be maintained may be from the NM cable clamps in the boxes/enclosures they enter/exit:
- (b) More Than One Conduit, Tube, or Raceway. Spacing between conduits, tubing, or raceways shall be maintained.

"Where" do the above conduit/tubes/raceways enter boxes/enclosures? That "spacing between" the conduits/tubes/raceways "shall be maintained".

If that "spacing" is the "spacing" which "shall be maintained", why would that be any different than the "spacing" between where the NM connectors where those NM connectors enter the boxes/enclosures.

*That* could very well tip the favor of interpretation in my favor and make my case "winnable", or at least make the opposing party's case "not winnable" such that I would win by default as the suing party would need to prove their case, and (b) certainly would override any "as long as the cables are not continuously touching" argument because the code acknowledges that "spacing" as being applicable to 'other wiring systems' and that "spacing" "shall be maintained", ergo, the spacing between the connectors for NM cable may well be considered the "spacing" which "shall be maintained" for NM cable as well.

Food for thought. I will await seeing you in court to decide this. :)

[Bill Kriegh]

I defy you to find any fastening system for NM-B, short of gluing them together with a continuous spacer, that maintains the same spacing between the cables, or any UL listed fastener that maintains the spacing of "box holes' and keeps the spacing "the same between cables" when used with multiple cables. If what you are pushing was actually what is required then you couldn't run more than one cable through a drilled hole (unless bigger than rules for drilling in framing allow). Even the article for requiring derating on a fire stopped hole references 2 cables in a hole

I've been doing this a long time and am well aware of the hows and whys of derating, and apply them when the situation requires it. I do, however, regularly take people to task who can't justify an inspection failure with a reference from the NEC that describes the situation. You haven't done that here. Even if I agreed with your reasoning for derating, which, incidentally, for the most part I do, I don't see a thing here requiring it applied like you want it to.

Come on Jerry, is there a part of "continuous length longer than 24 inches" that isn't clear? Is there something unclear about things having a "space maintained between them" that gets us to insinuating that the space has to be the same exact (width or length of) space? According to the dictionary if you maintain a space, you maintain an area where things don't touch. I'm not finding anything that says that that space has to be unchanging.

Again, knowing something to be what's intended because aunt Betty knows a guy whose brother is the employee of a boss whose partner plays golf with an engineer whose group leader sits on a code panel just doesn't cut it. Put it in writing and the problem goes away, sort of like your stand on marking tape and paint for some applications.

[Jim Port]

Jerry, I will say that no inspector I have met interprets the article the same as you and enforces it more like Bill sees it. If your interpretation was enforced even running cables parallel along a stud from a switch would be in violation as the spacing might waver from the distance between KOs. I see your side similar to your take on 312.8 and how it is seen by the trades and inspectors. BTW 312.8 now has that wording revised and does not say " for that purpose".

As in the original pic I can't see that being called bundled in the trade. Now the cables to the right side of that picture I would consider bundled.

[Harry Turner]

Jerry, I will say that no inspector I have met interprets the article the same as you and enforces it more like Bill sees it. If your interpretation was enforced even running cables parallel along a stud from a switch would be in violation as the spacing might waver from the distance between KOs. I see your side similar to your take on 312.8 and how it is seen by the trades and inspectors. BTW 312.8 now has that wording revised and does not say " for that purpose".

As in the original pic I can't see that being called bundled in the trade. Now the cables to the right side of that picture I would consider bundled.

Just for clarification, there are two pictures here. In the first picture, toward the back, you can see lines that are zip tied together. I would consider those bundled as well. In the second picture, to the right, I would agree with Jim that those are bundled. Anyone discuss zip tying bundled lines?

[Ronald Kornmiller]

Just for clarification, there are two pictures here. In the first picture, toward the back, you can see lines that are zip tied together. I would consider those bundled as well. In the second picture, to the right, I would agree with Jim that those are bundled. Anyone discuss zip tying bundled lines?

The (mostly) white items with the "wire"-ties look like PEX tubing and not like NM. In the first photo, there is a blue one breaking out of the bundle.

[Jim Robinson]

I saw the white wires as CATV or other low voltage. As for the bunching of the NM cable, it wouldn't be mentioned in my report, as I would not consider that to bundled or in contact for more than 24 inches.

[Lou Romano]

*Poof*

[Jerry Peck]

Derating of cables in a house that are never ever ever and I stress, never ever ALL loaded up continuously ... give me a break! There should be many more exceptions to the rules!

Ah ... but *there are no exceptions* to those rules. :D

The NEC has *not* decided that wiring in dwelling units does not need to be derated! :D

[H.G. Watson, Sr.]

Those cables running parallel are definately "bundled". Those perpinducular not. Howeber the butcherhing of the PRIs are concernng. Tearouts, etc. worthy of further exploration. Exposed wiring and sharing tearouts/knockouts with SED and communications cabling concerning. BTW, those webs are OSB not ply. More concerned about voids in bottom of photos and where in span/structural integrity and protection from damage perp. multiple rip-outs not knockouts or spec'd bored holes, than "bundling" issues; and tha suspected non-support (except by the strained cabling) of the drain. What else his spwas sharing/occupying space of this "utility" area, laundry facitilites:eek: ?

[Bill Kriegh]

I've know I'm not the only one that feels like I do about bundling and the 24 continuous inches. Check out the following product link, UL approvals and all, and then check out the fill chart.

http://www.aifittings.com/products/spec-sheets/cableway.pdf

[Richard D. Fornataro]

As an inspector, I would not consider the cables bundled together unless the installer employed the use of some mechanical means to ensure that such cables did indeed come onto contact with one another for 24 inches continuously. (ty wraps, etc.)

NM cables, properly sized for the branch circuit being fed, will not overheat under normal operating conditions. Consider the fact that even cables pulled through a raceway most likely are not in direct contact with one another for 24 inches continuously, however, I would use the derating table for such an installation as it seems conclusive that the intent of the code was meant for those installations, even though without Xray vision, I cannot verify that conductors abut, touch or do not maintain spacing. This is just common sense.

Since installations such as those depicted are customarily performed as long for as long as I've been an electrician, it would seem that ff the code was intended to compel derating of NM cables run adjacent to one another continuously, then it is my belief that wording to that extent would be specified in the code. (Or even the code handbook.)

The fact that #14 and #20 guage NM cable is already derated per code in residential installations makes it illogical to assume that further derating is necessary.

The code can be difficult to interpret as evidenced here in this forum. Differing opinions will always come into play and most inspectors do not perform inspections with the concern for how such would hold up in court.

Inspections should be performed with an understanding of the code and common sense. Speculation of the meaning or intent which is not demonstrably worded should not influence an inspection. Let the lawyers sort that out.

I am not intending the above as being directed towards anyone specifically in a nefarious or pejorative manner. It is obvious that some members of this forum seemingly demonstrate legal expertise or purport to have knowledge of such. Inspectors should use common sense. Do not read anything into the code that just isn't there. If I performed inspections in the manner that some of the posts in this forum contend to be enforceable, nothing would ever pass inspection and I would be in constant conflict with electrical contractors.

As I've indicated on numerous occasion to my supervisory personnel, "You didn't hire an attorney, you hired a licensed master electrician with 25+ years of experience in the electrical contracting field. If you wanted an attorney.....you should have hired one."

[ken horak]

............

[Jerry Peck]

I've know I'm not the only one that feels like I do about bundling and the 24 continuous inches. Check out the following product link, UL approvals and all, and then check out the fill chart.

http://www.aifittings.com/products/spec-sheets/cableway.pdf

Unless I missed it ... :p ... that does *not* say *derating does not apply*.

The NEC does not say you are not allowed to lay as many NM cables as you want side-by-side-by-side-by-side-by-... the NEC DOES say that *if you do that, then you shall derate the ampacity in accordance with that table. By the way, go to that table and you will see that you can put 10,000 NM cables side-by-side-by-side-by-side-by-... but if you do have more than 41 current carrying conductors (you would have 20,000 current carrying conductors) then you shall derate the ampacity to 35% of the listed ampacity.

So, go ahead and fill those suckers up ... just make sure you derate the conductors.

Bill, these supports solve the derating problem by separating the cables: CS4 Cable Standoff - Arlington Industries Resource Center (http://www.cepro.com/ai/product/cs4_cable_standoff)

[Mark S. Connely]

Jerry im loving it you are right

The ignorance of someone saying you can open a little space every 23 inches and continue bundling for another 23 inches is unreal thanks for wording it well

[Kristi Silber]

Well, I haven't read all the arguments about code and stuff in this thread, but I have a feeling this photo shows improper bundling...correct? These are connected to two 200 Amp C/B panels. I'm not familiar with this type of installation, where the NM is in PVC conduit. Is this the "raceway" some of you were talking about earlier, or is it called something else?

(I am not allowed to open the panel cover to investigate more throughly.)

[Jim Port]

Jerry im loving it you are right

The ignorance of someone saying you can open a little space every 23 inches and continue bundling for another 23 inches is unreal thanks for wording it well

You may think it is unreal or ignorance but that is what the wording says. This is no different than wiring in a nipple that is 24" or less not needing to be derated. Install a nipple 24 1/8" long and you would need to derate.

Sorry Mark.

[Kristi Silber]

Nevermind. I have read some of the posts here and in a related thread, and it must be wrong to wire like this. Just surprises me, because it's a well-designed and -built house otherwise.

[Bill Kriegh]

You may think it is unreal or ignorance but that is what the wording says. This is no different than wiring in a nipple that is 24" or less not needing to be derated. Install a nipple 24 1/8" long and you would need to derate.

Sorry Mark.

Careful Jim. I'm being put in my place - again

[Jerry Peck]

You may think it is unreal or ignorance but that is what the wording says.

Jim,

You keep saying that is what the wording says, but the wording does not say that. You are making words up.


This is no different than wiring in a nipple that is 24" or less not needing to be derated. Install a nipple 24 1/8" long and you would need to derate.
Jim, nipples and raceways longer than 24" are addressed separately from the "lack of maintaining spacing", nipples are just short raceways and the restrict the conductors ability to dissipate heat and stall cool, there is no "lack of maintaining spacing" requirement for conductors in raceways.

[Jerry Peck]

I have a feeling this photo shows improper bundling...correct?

Kristi,

There are other problems with that installation as well, but first a question: How long were those raceways, i.e., how far from the top of the panel to the ceiling?

[Jim Port]

I was using the nipple as another example to counter Marks view about a slight difference in length making a difference between needing to derate or not.

I am taking the stance that if the spacing is not maintained they would be in contact. Not that the spacing must a a defined or constant amount. If they are not continuous for 24" or more than that section does not apply. This is that way that every electrical inspector in my experience has seen this issue.

[Jerry Peck]

I was using the nipple as another example to counter Marks view about a slight difference in length making a difference between needing to derate or not.

Jim,

I fully understand that point, but they have to draw the line in the sand someplace ... is it 6" - 12" - 24" - 5' - 10'?

I am sure that there were some calculations used at some point which showed that 12" was 'no big deal' but that 48" was a 'big deal', so for safety they backed it down to 24" instead of some intermediate number to give a 'greater safety factor' in the number.

[Jim Port]

I guess I could have also used the 3 hour rule concerning continuous loads. Two hours 59 minutes = non-continuous. Leave it on another minute and it is now continuous and would need to drop to 80% of the breaker rating.

[Jerry Peck]

I guess I could have also used the 3 hour rule concerning continuous loads. Two hours 59 minutes = non-continuous. Leave it on another minute and it is now continuous and would need to drop to 80% of the breaker rating.

Like speed limit signs where 60 mph is okay but 61 mph is not. :)

[Jim Port]

Like speed limit signs where 60 mph is okay but 61 mph is not. :)

Did someone tell you that speed limits were that low? I have heard the Jag likes to cruise a little faster than that. :D

[Kristi Silber]

Kristi,

There are other problems with that installation as well, but first a question: How long were those raceways, i.e., how far from the top of the panel to the ceiling?

I believe they were about 3 1/2 ft. This house has 10 ft. ceilings.

I suspect the homeowner "installed" the ceiling drywall. Wish I could see above it.

Here are the panels the raceways were above, FWIW, both 200 Amp.

[Richard D. Fornataro]

I believe they were about 3 1/2 ft. This house has 10 ft. ceilings.

I suspect the homeowner "installed" the ceiling drywall. Wish I could see above it.

Here are the panels the raceways were above, FWIW, both 200 Amp.

The installation that you have pictured is typical here in upstate NY.
The cables are installed in PVC for the purpose of protecting such from "physical damage" where exposed to such.
"Physical Damage" is what is usually the determining factor of "uses permitted" as it pertains to NM cable.

No one has commented on the fact that I raised in a previous post regarding the fact that NM cable is already derated for residential wiring in the first place.

I have NEVER observed NM cable installed in a manner consistent with this thread to be subject to overheating or derating for that matter.

Again, the opinions of some posters here would result in very few installations being approved and I feel that the opinions reflected here are often extremely stringent and interpret code in a manner that is inconsistent with reality.

Once again, I am not an attorney, I am an electrical inspector.

If they wanted attorneys inspecting such, then hire them.

For an inspector to perform in the capacity required, they should have a plethora of field experience so that they may apply code in a realistic manner.

Leave the strict interpretations for litigation testifying.

Show me ONE example of NM cable overheating in such an installation....just one.

If properly sized for the branch circuit being fed....THERE WILL BE NO PROBLEM and there is no rational reason to derate such.

[jim baird]

Incidentally an electrician called me about his helpers putting romex in conduit like in Kristi's pics. He wanted to know if I objected, and I listened to his reasoning about neatness, short length of the conduit, and the fact that many residential circuits go unused most of the time.

I agree with Richard, that hardline by the bookism may be appropriate for litigation it falls short of day to day practicality.

I am the AHJ for two small local bodies here, as my home inspecting is slow as molasses in winter these days.

[Kristi Silber]

I appreciate the comments about the photo I posted. This discussion makes me wonder how different types of conduit/armor disperse extra heat. I would think PVC would be less able to conduct heat away from cables within.

I'm interested in the other things Jerry mentioned he saw wrong with the installation. Cables going directly through drywall?

[Jerry Peck]

I'm interested in the other things Jerry mentioned he saw wrong with the installation. Cables going directly through drywall?

Kristi,

Are those panels in a garage? If so, the openings in the ceiling around the conduits are a concern for lack of separation as required.

The NM cables coming out of conduit marked '4' is nice and tightly tied together, and, despite what some say above, the NEC *REQUIRES* derating in residential installation ... whether those individuals like it or not, or whether those individuals agree or not. The same applies to the NM cables coming out of the conduit marked '6'.

The conduits marked '1' and '2' extend up into the ceiling and are required to end below the ceiling. The same for the conduit marked '5', and possibly for the conduit marked '7'.

The tops of the conduits need to be terminated in a proper fitting which protects the NM cables from damage from sharp edges in the conduit, a bushing would work 'best'.

Additionally, the conduits are supposed to be sealed at the tops.

The NM cables are required to be properly supported and secured within 12" of the where they exit the conduits.

And, of course, as I stated at the beginning, at 3-1/2' long, the NM cables need to be derated, and if any of those NM cables go into the attic, the derating for ambient temperature needs to be taken as well.

Let's take the conduit marked '4' as an example:
- I see 5 2-conductor NM cables there, and the bundle looks like there are at least 2 more cables behind the ones which are visible. That means there are 7 2-conductor cables in that conduit, and that the number of current-carrying conductors is 14 (7 x 2 = 14).
- Let's presume those are older NM cables and that they may be 12 AWG conductors which have an ampacity for derating of 30 amps.
- The derating factor for 14 current-carrying conductors is 50, multiply the 30 amp ampacity for derating times 50 and you get a derated ampacity of 15 amps. And that is with *no* derating for high ambient in an attic.
- Those 12 AWG NM cables would require overcurrent protection *no greater than* 15 amps.
- Now let's presume that those NM cables also go into the attic, and that the attics in your area get to, say, about 135 degrees F in the summer. The derating for that ambient temperature is 0.71. We now multiply the 15 amp derated ampacity times 0.71 for a new derating of 10.65 amps, which means that those 12 AWG NM cables are only suitable for a 10 amp overcurrent device - try to find a 10 amp breaker! :D

There will be some responses which say the above is not applicable to residential, or that it is not needed, however, that is *THEIR OPINION* as 'feel-good' chatter, however, the NEC *REQUIRES* that derating be applied.

They also talk about 'that only applies when you go to court', well, THE REASON it went to court is because it was installed wrong, not derated properly, and now the whole mess ends up in court and THEN ... that is when they say 'Oh, yeah, NOW we will apply the derating factors'. But if they had been paying attention and applied the derating factors FIRST they would not be 'in court'. Sheesh, one wonders what they are thinking - they WANT to end up in court so they can apply the derating factors???

"First Preventers" ... remember that from another post I made recently? :D

[Kristi Silber]

Jerry, thank you very much for the informative post. Electrical systems are definitely my weakest spot, and I've learned so much from this forum.

This is a house built in 2000. The panels aren't in the garage, and there is no attic. (Flat roof, very modern, has a huge curved sound shield perched on the front. $1.1 mil in today's market. A fun one to survey.) These aren't people who want to be limited in their amperage, so it's pretty safe to say the cables are not derated.

I was just reading that the most common thing to ignite first in a distribution and lighting res. electrical fire is the wire insulation.



Let's presume those are older NM cables and that they may be 12 AWG conductors which have an ampacity for derating of 30 amps

For all know, it could be 10 AWG. Ten foot ceilings, too high to see.

[Richard D. Fornataro]

Just some random thoughts regarding a recent post.

Conduits require ends......chases do not.

Since we seem to have "Litigation Consultants" pontificating on electrical inspection practices employed in the real world and not a courtroom, if not derating such installations results in litigation, provide one example of NM cables being bundled in such a manner causing a fire or even overheating that resulted in such a litigious circumstance.

Just one. that's all I ask.

If all inspectors scrituinized installations in the manner professed in this forum on a continual basis by consultants:

A) Nothing would ever pass their unrealistic expectations
B) The plethora of complaints lodged against such an inspector would result in their untimely removal from such a position.

I'm not trying to personally retaliate against anyone but some of the opinions as expressed in this forum are absolutely ludicrous.

And providing such unrealistic opinions to self-professed new HI's is deleterious to that profession as well.

I would speculate that NM cable bundling will be encountered in a majority of home inspections.

I've engaged in the practice of wiring residential properties in this customarily accepted manner and have stamped inspections utilizing such without compunction.

To write such up and possibly cause a homeowner to expend funds to ameliorate such an ordinary and accepted practice will complicate numerous real estate transactions un-necessarily.

I've been installing and inspecting for 30+ years and have never been subject to nor participated in such rigid interpretations of the electrical code.

If my opinion as reiterated is incorrect, then let other experienced electrical inspectors and licensed master electricians admonish me and I will reconsider my estimation of such a practice.

I have never seen nor heard of any problems resulting from such a practice provided that the branch circuits are installed properly in the first place.

To those whom interpret this Marine Corps veteran as being ascerbic in my commentary, I can assure you there is no disrespect intended.

It's just that enough is enough!

[Raymond Wand]

Richard

Right On! Thank you.

[Kristi Silber]

"And providing such unrealistic opinions to self-professed new HI's is deleterious to that profession as well."



I think you mean me. Actually, I'm not a HI at all, I do surveys for insurance companies. We aren't trained to go into this kind of detail, but I like to know about potential safety issues anyway.

I'm obviously not knowledgeable about this stuff to take a stance, but "better safe than sorry" seems to me a reasonable view when it comes to code and fire safety.

Here's a report of an experiment measuring temperatures of bundled NM. The authors suggest the code isn't conservative enough is its requirements for bundled NM. Just one, unrepeated experiment, but worth considering.
http://www.copper.org/applications/electrical/building/pdf/bundle_evaluation_report.pdf

This site suggests that bundling is one of the top reasons electrical inspections fail in a MD county - so evidently some inspectors, anyway, do write it up.
http://frederickcountymd.gov/documents/Permits%20&%20Development%20Review/Permits%20&%20Inspections/Inspections/Top%20Ten%20Reasons%20Res%20%20Electrical%20Inspec tions%20Fail%20final.PDF

[Jerry Peck]

Conduits require ends......chases do not.

They do where the cables and conductors exist so as to not damage the cables and conductors.


If all inspectors scrituinized installations in the manner professed in this forum on a continual basis by consultants:

A) Nothing would ever pass their unrealistic expectations
B) The plethora of complaints lodged against such an inspector would result in their untimely removal from such a position.

Inspections DO pass because the contractors learn that the code they say they are building to is the same code they are being held to.

Do you tell your customers and AHJ that you don't care what the code says, that you are going to do it *YOUR WAY*? I'm guessing that your contracts state that you will do the work in accordance with the codes ... and here you are complaining about being held to the same codes you contracted to be held to.

Sounds a bit two-faced to me, not that I am trying to retaliate against anyone for them being absolutely ludicrous and two-faced ... :rolleyes:


And providing such unrealistic opinions to self-professed new HI's is deleterious to that profession as well.

Expecting contractors to be held to the code the contractors say they are performing to is deleterious to the profession? You have it backward - CONTRACTORS not wanting to perform to the code THEY SAY they will perform to is deleterious to their trade.


I would speculate that NM cable bundling will be encountered in a majority of home inspections.

And in the majority of AHJ inspection too, but that does not make it right, and the contractors obligation is to do what they said they would do - - - NOT ONE CONTRACTOR has come into the building department and said "I am going to do this job the way *I* want to, to heck with the codes.", that is because they know they would not be issued a permit if they said that.


I've engaged in the practice of wiring residential properties in this customarily accepted manner and have stamped inspections utilizing such without compunction.

Is that your way of saying to you do not wiring to the codes, and you know that, and you just do not care?


It's just that enough is enough!

Correct: Enough is enough, and it is enough of contractors saying to disregard the codes because *THEY* don't think they should do the work that way. Absolutely correct - enough of that crap work is enough!

[Jerry Peck]

Here's a report of an experiment measuring temperatures of bundled NM. The authors suggest the code isn't conservative enough is its requirements for bundled NM. Just one, unrepeated experiment, but worth considering.
http://www.copper.org/applications/electrical/building/pdf/bundle_evaluation_report.pdf

This site suggests that bundling is one of the top reasons electrical inspections fail in a MD county - so evidently some inspectors, anyway, do write it up.
http://frederickcountymd.gov/documents/Permits%20&%20Development%20Review/Permits%20&%20Inspections/Inspections/Top%20Ten%20Reasons%20Res%20%20Electrical%20Inspec tions%20Fail%20final.PDF

Kristi,

More inspectors write up bundling than most electricians think ... until the inspectors in their area get a clue and start writing the local electricians up, then they scream and cry like a baby that the inspectors are picking on them.

The contractor submits the plans and drawings to the building department for approval, and those plans and drawing need to meet code minimums. Then the contractor tries to build it differently and complains that the inspector is picking on them for not doing what they said they would do. Sheesh! Who would of thunk that the contractor would actually do what they said they would do? :rolleyes: :D

[Kristi Silber]

Now, now, no fair generalizing, I'm sure there are lots of contractors out there who follow code conscientiously. But it's too bad that there are so many exceptions. I won't say more than that - this is one debate I'll stay out of.:cool:

[Richard D. Fornataro]

They do where the cables and conductors exist so as to not damage the cables and conductors.



Inspections DO pass because the contractors learn that the code they say they are building to is the same code they are being held to.

Do you tell your customers and AHJ that you don't care what the code says, that you are going to do it *YOUR WAY*? I'm guessing that your contracts state that you will do the work in accordance with the codes ... and here you are complaining about being held to the same codes you contracted to be held to.

Sounds a bit two-faced to me, not that I am trying to retaliate against anyone for them being absolutely ludicrous and two-faced ... :rolleyes:



Expecting contractors to be held to the code the contractors say they are performing to is deleterious to the profession? You have it backward - CONTRACTORS not wanting to perform to the code THEY SAY they will perform to is deleterious to their trade.



And in the majority of AHJ inspection too, but that does not make it right, and the contractors obligation is to do what they said they would do - - - NOT ONE CONTRACTOR has come into the building department and said "I am going to do this job the way *I* want to, to heck with the codes.", that is because they know they would not be issued a permit if they said that.



Is that your way of saying to you do not wiring to the codes, and you know that, and you just do not care?



Correct: Enough is enough, and it is enough of contractors saying to disregard the codes because *THEY* don't think they should do the work that way. Absolutely correct - enough of that crap work is enough!


Sometimes it is better to remain silent and be thought of as ignorant than to speak and remove all doubt.

You're opinions are inconsistent with reality.

I am seriously doubting you have endeavored in the field other than in a courtroom.

Your commentary continues to reflect that your livelihood is derived from twisting the truth and refusing to comprehend that which is written.

If you had field experience you would know that you don't close a chase.

You have failed to respond to the challenge of citing any incidence where such a practice results in catastrophic results.

You continue to pontificate ad nauseum concerning code but your commentary reflects the fact that you do not exist in the real world.

I will match the respect I receive from my peers against your erratic spewing of codes any day.

Make all the derogatory comments you like.

I think the patrons of this forum know you for what you are.

"When people show you who they are.......believe them."

In the future, I will choose not to argue with your delusional view of inspection practices simply because I don't have to.

The past reflects that to continue such is an exercise in futility.

The best way to handle a child throwing a tantrum is to ignore them.

Have a nice life.

[Jerry Peck]

I am seriously doubting you have endeavored in the field other than in a courtroom.

Then you most certainly have not been reading what I write. :rolleyes:

No wonder there is a lack of communication debating with you ... you cannot carry on a debate unless you pay attention and follow what the other person says (writes). :rolleyes:


The best way to handle a child throwing a tantrum is to ignore them. Then I shall try to ignore you.

[Kristi Silber]

Sometimes it is better to remain silent and be thought of as ignorant than to speak and remove all doubt.

You're opinions are inconsistent with reality.

I am seriously doubting you have endeavored in the field other than in a courtroom.

Your commentary continues to reflect that your livelihood is derived from twisting the truth and refusing to comprehend that which is written.



I should really stay out of this, but I just have to say I find these comments utterly ridiculous and totally unfounded.

And I find it frightening that an electrician will flaunt in public the fact that he doesn't follow code as a contractor OR inspector, especially since his comfort in doing so must mean that there are others doing the same thing.

[Bill Hetner]

Kristi, anybody that says they will not comply to codes to officals or others is just waving a red flag at a bull. they are looking for a fight that they are not going to win in the long run. reason being is if you say that regularly and word get's around there will always be someone out there to take you down.

Yes codes do not get followed all the time, but when they get caught there is a price to pay for it. it's like speeding we all do it sometimes and sometimes we get caught. but not all the people will be caught, some that do are involed in accidents and death's. the same thing happens in non code compliance.

as for the fighting and disagreements they will always be there, sometimes you have to put on blinders on and focus on what is right or questionable and try and learn the differance

[Raymond Wand]

Code is open for interpretation.

The Building Code in Ontario routinely has appeal hearings for those who wish to question the code.

Sometimes the code is upheld other times it is interpreted in another way and what the respondent is asking for is granted.

Appeals & Approvals (http://www.mah.gov.on.ca/Page7391.aspx)

Appeals & Approvals

A fair and effective building regulatory environment provides mechanisms whereby decisions of enforcement officials can be appealed, and where innovative building materials may be approved and introduced to market. Accordingly, Ontario's Building Code Commission operates as an expert adjudicative body where Building Code disputes are heard in a timely manner. In addition, the Building Materials Evaluation Commission and Minister's Rulings serve as ways to receive evaluation and approval for new building products.

[Richard D. Fornataro]

Mr. Peck,

Please DO ignore me.

To all other posters to this forum,

Anyone who thinks that I was indicating that I choose to not follow codes is mistaken.

What I did indicate is that nobody I know would derate NM cable installed in the manner originally posted.

It's that simple.

Just because one person chooses to peck at every word, phrase and sentence written by everyone in this forum does not make their opinion weigh anymore heavily than anybody else's.

I'm counting on a majority seeing my point of view on this.

If not, I'll take the hint and stop posting.

Thank you.

[Raymond Wand]

Richard

Don't stop posting. I enjoy your retorts.

[Jerry Peck]

Anyone who thinks that I was indicating that I choose to not follow codes is mistaken.

That's not the way you put it previously, but that's good to know.


What I did indicate is that nobody I know would derate NM cable installed in the manner originally posted.

You seem to live in a different world than many of us, take Kristi's link at bundling being one of the main write-ups there ... and that is not the only place. The world is an ever changing place and as codes are adopted in more places, codes are more closely followed in places where they have already been adopted, it's the natural progression of things: more people becoming familiar with codes leads to more knowledge of the codes, and more knowledge of the codes leads to greater enforcement of the codes as the overall intent of the codes of to protect the health, welfare and safety of the public, and ignoring what is adopted as "the minimum standard" leads to bad things happening.

Cheers! :)

[Jerry Peck]

Just because one person chooses to peck at every word, phrase and sentence written by everyone in this forum does not make their opinion weigh anymore heavily than anybody else's.

Trying to defend a practice which has long been acknowledged as creating a potentially hazardous condition is ... well ... "indefensible".

As you obviously feel there is no harm in the practice being discussed, how about if you submit a code change and have them just remove that section? If they remove it, I will agree with you, but until then, I am in agreement with the code.

[Kristi Silber]

Anyone who thinks that I was indicating that I choose to not follow codes is mistaken.

What I did indicate is that nobody I know would derate NM cable installed in the manner originally posted.




Richard, isn't this a contradiction? It looks to me like there are at least 6 cables bundled for at least 24 inches, in direct contact with each other. That's against code. (And please don't stop posting just because of a disagreement about this one thing! But also please don't make assumptions about others' experience. In Jerry's case you are most definitely wrong.)

Raymond, I'm sure some parts of code are open to interpretation; most lengthy documents are. But that doesn't necessarily mean that the code itself is flexible, it just means that parts may be read differently by different people. There may well be instances when circumstances are such that the reasons behind the code don't apply, and exceptions are appropriate (um, bundling through exterior conduit in the Arctic Circle?). The problem is when contractors (or inspectors) take it upon themselves to disregard code just because they feel it's generally unnecessary or overly stringent.

[Raymond Wand]

Raymond, I'm sure some parts of code are open to interpretation; most lengthy documents are. But that doesn't necessarily mean that the code itself is flexible,

We'll have to disagree. In Canada the Chief Building Official has the power to review and accept alternative solutions to the code. There is also an appeal right where the building code can be enforced as written or the panel can allow a variance.

Electrical issues do not come under the purview of the building code officials that is separate and overseen by the Electrical Safety Authority (ESA). I can tell you from first hand experience exceptions to the electrical code do take place. I have seen a number of issues which are contrary to code which are routinely overlooked by ESA inspectors. Typical example is a double tap of 16 gauge wire from door bell double tapped with solid 14 gauge wire on a breaker only rated for one conductor.

Another case the pvc conduit should not be fed underground to a main panel, yet the local ESA inspector approved the installation which included the conduit being brought in under grade to the panel in the basement.

We don't live in a perfect world and even though I would like to think we do, I know better than to say everything is perfect, even code officials turn a blind eye to issues.

The definitive test is the court of law, and even then you will have experts contradicting one another.

[H.G. Watson, Sr.]

Yes they would require additional derating Kristi. The "exposed" method and choice of material is likewise compromised.

The additional derating is required so as to maintain integrity and not melt, catch fire, vaporize, etc. the insulation and not overheat the conductors themselves should there be a maximum available fault current/short circuit exposure condition - it/they must maintain its/their integrity so that the protection system can respond; and additionally withstand the effects of the incredibly strong electomotive force in the circuit(s) during a maximum available fault current condition. This is also one of the many reasons why we restrain, clamp, etc. conductors, but require "slack"/work length at junctions, etc.; secure equipment; brace busses, main circuit breakers on service equipment, back fed breakers, etc. Path of return to source means the utility transformer.

SCCR (short circuit current ratings), AIC (available interrupting current) ratings or AIR (ampere interruption rating) and temperature ratings are important considerations along with the available fault current. (This is also why those "wire nuts" on your little old lady's service drop are so dangerous and a major red flag for your insurance surveys as well).

AIC applies to protective interrupting devices such as circuit breakers and fuses. The unit of measure for AIC is Amps RMS Symmetrical. typically in range of 5K to 200K amps describes the maximum fault current that the protective device can clear safely without welding closed or causing damage to equipment or personnel.

SCCR applies to complete pieces of equipment or components such as racks, cabinets, or subassemblies such as busses, etc.. The unit of meaure is also Amps RMS Symmetrical and describes the maximum fault current that the euqipment can withstand safely or the maximum available fault current of the feeder to which the equipment can be safely connected.

Available fault current, AIC ratings of protective devices, and SCCR of switchgear and utilization equipment must be coordinated from the utility transformer to the last outlet in the system.


At every point in the system, the available fault current can be calculated, and the engineer must insure that it does not exceed the AIC of protective devices or SCCR of equipment installed at that point.
The engineer has tools availble for limiting available fault current, the most common being wire length. The impedance of a wire run means that the longer the run, the lower the availble fault current at the end of the wire. Other devices such as electronic current limiting circuit breakes and current limiting fuses have a characteristic known as let-through current. These devices can be used to limit fault current when equipment with a low SCCR must be connected to a source of high available fault current, and no long run of wire is possible.

It is interesting to note that fault current translates into incredibly strong electromotive force in the event of a short circuit. This is the reason that one will often hear statements like "that bus bar is braced for 100K amps". Not only does the bus bar have to avoid melting in the presence of a short circuit, it also has to be restrained so that it does not RIP OFF ITS MOUNTS when the fault occurs.

Its not just the every day utilitzation alone that is considered by the requirements of the code, it is also the easily foreseen albiet rare events that for safety protection of property and preservation of LIFE, must be designed for.


HTH.


P.S. Keep in mind that things are quite different in Canada, especially in the province of Ontario. Legal issues, code issues, goverement owned utilities, and the Electrical Safety Authority are entities and constructions that are completely different from what we have here in the United States, even their form of government is quite different, most especially their court system and common law/strict liability issues.

[Kristi Silber]

"Variance" - that's the word I was looking for. Raymond, I think you misinterpret me a little. I was saying that there are some conditions under which code may not apply because the circumstances don't merit it...and then a variance, after due consideration, is warranted. There may also be parts of a code that are outdated because new evidence or materials or whatever determines that they are unnecessary. My problem is with people who ignore parts of code because they personally don't think it's valid although the evidence says otherwise.

Bundling can be a hazard. That's been demonstrated. Maybe it's not an issue the majority of the time because the circuits aren't used continuously or at high enough amperage to make a difference. But our electricity usage continues to grow, people leave their 4' TVs on 24/7, bake a turkey for 5 hours in an electric oven, run a bunch of electric space heaters, whatever...and if the NM in the middle of the bundle can't dissipate the heat it could be a problem. No one knows what demands will be placed on those cables in the future. Code is there for a reason, and it shouldn't be taken lightly.

EDIT: Above was posted without having seen HGW's post.

Sometimes I frankly have a little trouble absorbing your posts immediately, but some stuff sinks in and over time I can make sense of it all - and appreciate the detail you go into.


The additional derating is required so as to maintain integrity and not melt, catch fire, vaporize, etc. the insulation and not overheat the conductors themselves should there be a maximum available fault current/short circuit exposure condition


Based on what I've read through Googling, this isn't always the case. Even under some ordinary circumstances of continous loads, especially in warm areas like attics, as Jerry pointed out, or when a bundle has insulation or fire retardant foam around it, the cables can heat up enough to be damaged. No fault is required for a problem to arise.

[H.G. Watson, Sr.]

EDIT: Above was posted without having seen HGW's post.

Sometimes I frankly have a little trouble absorbing your posts immediately, but some stuff sinks in and over time I can make sense of it all - and appreciate the detail you go into.


Based on what I've read through Googling, this isn't always the case. Even under some ordinary circumstances of continous loads, especially in warm areas like attics, as Jerry pointed out, or when a bundle has insulation or fire retardant foam around it, the cables can heat up enough to be damaged. No fault is required for a problem to arise.

Ambient temperature is yet another derating "step" or consideration. Insulation contact - i.e. restriction of free air contact is yet another when applying for example NM or similar (such as UF cross-referenced) wiring methods. The "protection" if plastic (Sch 80) or metal, exposure to direct sunlight, are additional considerations. The installation location conditions - wet, damp, dry, exposed or covered wiring methods, etc. Stapling too tightly causing heat build-up under the staple, the list goes on.

I suggest you review some of the extensive discussions already present on this board as well, but if you're going to debate "the code" I suggest you learn some electrical theory first, then read the code itself. IOW read/study more, debate less.

There are a number of free "modules" and training materials available on such subject areas including electrical inspeciton available on the web, if you're truly interested in learning more.

[Kristi Silber]

You are right that I should study more on my own. However, I have not debated anything in this thread that I don't understand. I was not debating your earlier point, merely pointing out that circumstances beyond those you described also come into play, just as you wrote in your latest post.

I'm here primarily to learn. Debating can itself be an education. I don't wish to refrain from discussion until I've read the whole NEC, nor do I think I should have to.

[Lou Romano]

***Poof***

[Kristi Silber]

I feel I owe Mr. Watson an apology. In post #63 I only saw what he'd written in #62 after writing most of mine, and because of that did not try at the time to thoroughly understand him but instead latched onto an aspect he hadn't included but that I'm sure he knew about already.

I found particularly interesting the discussion of the energy of a fault being transformed into electromotive force, something I hadn't considered. Also interesting was the effect of wire length on impedance. After reading his post a few more times I'm better able to absorb it; it's good to begin to understand the ratings of the system as a whole and what affects them (still need to look up a few terms, but I'm almost there!)

Thank you kindly, Mr. Watson!

You'll see...considering where I started out, I've learned a lot already in the short time I've been around here; give me a little time and I will become more comfortable with the terminology and better able to appreciate, grasp and discuss the details.

[Bill Kriegh]

Part of being an electrician, and electrical inspector, is knowing and understanding that there are exceptions to a lot of things. So, after beating to death what constitutes bundled cable, spacing, and a sink or two, I'll go ahead and stir this into the mix.

What this says is that if you have a cable that is rated at its' full ampacity (this means that there are portions of the circuit that would be capable of being used at their rated current if not for a portion of the cable being subject to derating) and conditions change so that the ampacity is now reduced on part of the cable, the "change" is ignored for ten feet or less. I'll leave it to your imagination as to how I think this applies to, say, wire in an attic, cables in close proximity whether they touch or not, multiple cables in a conduit exiting the top of a panel that leave the conduit in a non structural ceiling where they aren't bundled, and a few other situations.


2011 NEC
310.15 Ampacities for Conductors Rated 0–2000 Volts
(A) General.

(2) Selection of Ampacity. Where more than one ampacity
applies for a given circuit length, the lowest value shall be
used.
Exception: Where two different ampacities apply to adjacent
portions of a circuit, the higher ampacity shall be permitted to
be used beyond the point of transition, a distance equal to 3.0
m (10 ft) or 10 percent of the circuit length figured at the
higher ampacity, whichever is less.

[Kristi Silber]

I'm going to see if I understand this with an example, and you guys can correct me. You have a 60' circuit, mostly with an ampacity rating of 25. Between a switch and a light is a stretch of cable derated to 12.5 because of bundling in the attic, but if that stretch from the switch to the bulb is only 5', it's okay. Is that what's meant by adjacent portions of the circuit? Is it because on short stretches there's little impedance?

Sheesh, I think if I get a hard copy of the NEC it better be the illustrated one! (Even if code is determined by lawyers and lobbyists, it's definitely written by electricians!:D )

[Jerry Peck]

Kristi,

Before one can even consider applying that 10% rule (or 10 feet, whichever is LESS, and usually 10% would be less), one must first make a presumption that whoever screwed up the installation ONLY screwed up the installation in that one area.

The more reasonable presumption would be that when someone screws up an area, they likely screw up a lot more than one sees.

Let's take you example of a 60 foot circuit and there is 5 feet which visually requires derating ... unless you can see the entire circuit and its installation, it would not be reasonable to presume that the installer ONLY screwed up that 5 feet you can see, but that they screwed up other areas too.

To apply that exception to "the lowest value shall be used" one MUST be able to see and document that, indeed, only one some area was screwed up - that ALL other areas were installed correctly. I present the idea that it would be next to impossible, in almost all installations, to document that all other areas were correctly and properly installed and that the exception could be applied.

Now, Bill, I suppose he has x-ray vision and can see what others cannot see, and therefore Bill may be able to apply exception to all of his installations and inspections.

Me, I am a mere mortal, I do not have x-ray vision and therefore cannot see through walls, past ceilings, etc., the only way I can see inside the walls is at electrical rough (before the insulation and drywall goes on) and that is when I see all the screwups the installers have made, and I can clearly see that there might be 10% WHICH IS ACTUALLY CORRECT. :)

That is, until after they make the corrections I point out, in which case I may have missed, at most, that overall 10%, and that exception nicely covers what I may have missed. :D And I am okay with that. :cool:

[Kristi Silber]

Oh, yes, of course - I wasn't talking about the real world. I just wanted to make sure I understood what the code was saying.



unless you can see the entire circuit and its installation, it would not be reasonable to presume that the installer ONLY screwed up that 5 feet you can see, but that they screwed up other areas too.




Ah, but the way the code is stated, it applies to adjacent areas, so you've increased your odds a bit. :D As I understand it, the stretch that can be excepted must be less than 10% (or 10') regardless of other derated, nonadjacent stretches. So on a 100' circuit you could have 20' of 25 amp, an outlet, 5' of normally-derated-but-excepted, an outlet, another 20' of 25 amp, a switch, 7' of bundled-in-the-attic, a light, then more 25 amp cable and you'd be fine.

But what do I know?!?:rolleyes: Believe me, I'm not trying to argue with anyone, just trying to understand. I don't even know why, I certainly won't use it in my present job. I'm interested in the reasoning behind the rules - and exceptions.

[Bill Kriegh]

Super electrician I'm not, and I don't make a habit of wiring using all the "outs" for various rules in the NEC, even the ones I rant on and on about here.

What I do, however, is take folks to task for what I think is reading too much into what's written, or maybe not reading enough of what is written.

I, for one, accept that the NEC folks put articles like this in the book because they expect them to be used. Others appear to view them as a impediment to a strict and unwavering view of how things need to be done. Of course, I don't automatically assume the entire job is done wrong, either, and that reasonably competent people are doing the work. I also don't take the view that using these articles on occasion is doing "screwed up work" - it's entirely legal, and it would appear the situation has cropped up more than once or it wouldn't be in the NEC. Of course, I also take the view that the "circuit" is all the cable protected by a circuit breaker, not just the cable from a switch to a light fixture, and that most circuits in a residence probably run close to 100 feet or more of cable. And, if we assume that there are a number of places where this circuit has branches running into a hot attic to a lighting outlet, the rule can be applied multiple times.

[Bill Kriegh]

Oh, yes, of course - I wasn't talking about the real world. I just wanted to make sure I understood what the code was saying.



Ah, but the way the code is stated, it applies to adjacent areas, so you've increased your odds a bit. :D As I understand it, the stretch that can be excepted must be less than 10% (or 10') regardless of other derated, nonadjacent stretches. So on a 100' circuit you could have 20' of 25 amp, an outlet, 5' of normally-derated-but-excepted, an outlet, another 20' of 25 amp, a switch, 7' of bundled-in-the-attic, a light, then more 25 amp cable and you'd be fine.

But what do I know?!?:rolleyes: Believe me, I'm not trying to argue with anyone, just trying to understand. I don't even know why, I certainly won't use it in my present job. I'm interested in the reasoning behind the rules - and exceptions.

By jove! I think you're getting the hang of this - - and it's going to drive Jerry nuts.

[Kristi Silber]

I also take the view that the "circuit" is all the cable protected by a circuit breaker, not just the cable from a switch to a light fixture


I do too. The "portions" of the circuit are switch-to-fixture or whatever.



What this says is that if you have a cable that is rated at its' full ampacity (this means that there are portions of the circuit that would be capable of being used at their rated current if not for a portion of the cable being subject to derating) and conditions change so that the ampacity is now reduced on part of the cable, the "change" is ignored for ten feet or less.


I may be misinterpreting, but it sounds like you are saying, for example, that if you have a stretch of 20' cable on a 100' circuit and 5' of it are bundled in the attic, that stretch of cable does not have to be derated. Is that what you mean?

What I'm most interested in is the reason for the exception.

[Darrel Hood]

Jerry,
Using your logic described in post #70, if one observes problematic bundling in one location, one should assume the same problem exists on all circuits installed by the same electrician. I am unsure by what logic you draw a line. I believe an HI can only identify a problem he sees.

[Roger Frazee]

2011 NEC
310.15 Ampacities for Conductors Rated 0–2000 Volts
(A) General.

(2) Selection of Ampacity. Where more than one ampacity
applies for a given circuit length, the lowest value shall be
used.
Exception: Where two different ampacities apply to adjacent
portions of a circuit, the higher ampacity shall be permitted to
be used beyond the point of transition, a distance equal to 3.0
m (10 ft) or 10 percent of the circuit length figured at the
higher ampacity, whichever is less.[/quote]



This is a part of NEC code that I agree leaves you with a lot of imagination to work with ....:)

I've never used that code section in residential but my read of the exception is it targets single circuits that only have TWO ampacity considerations. I would also think that you couldn't consider any circuit serving general purpose receptacles. A likely place to use it would be a HVAC circuit to a roof top unit where you would have an adjustment for the new rooftop exposure multiples/rules. So the portion of the circuit on the roof top would have less ampacity than the portion of the circuit not on the rooftop.You could not consider IMO several (more than two) sections of changing ampacity.

I also do not think this exception gives permission to ignore bundling for NM or derating more than 3 ccc's in conduit not on a rooftop, I think it is speaking to single circuits to a known load.

I think this way becuase if you consider several circuits in conduit or bundled NM what are the odds that all the circuits are the same length to where you would be allowed to ignore bundling or derating for all of them.

But I confess I need to review this more as it is a section of code that I am not overly familiar.

[Jerry Peck]

Ah, but the way the code is stated, it applies to adjacent areas, so you've increased your odds a bit. :D

Not really as there is another adjacent area just beyond the adjacent area you may be able to see, but not be able to see the next adjacent area. :)


As I understand it, the stretch that can be excepted must be less than 10% (or 10') regardless of other derated, nonadjacent stretches. So on a 100' circuit you could have 20' of 25 amp, an outlet, 5' of normally-derated-but-excepted, an outlet, another 20' of 25 amp, a switch, 7' of bundled-in-the-attic, a light, then more 25 amp cable and you'd be fine.

Except that it does not say that. ;)

The code is silent on whether or not the 10% (or 10', whichever is smaller) is the maximum for the entire circuit and the code is presuming that the installation was correctly done but that there was some condition which caused this one area to be done this way, and as such is excepted.

Otherwise one could have, worst case, a 100' circuit with 10' not derated, 10' derated to 10.5 amps, 10' not derated, 10' derated to 10.5 amps, 10' not derated, 10' derated to 10.5 amps, 10' not derated, 10' derated to 10.5 amps, 10' not derated, 10' derated to 10.5 amps,

I doubt the code is written to allow 50% of the circuit to be derated but excepted out.

Now I have to read what Bill and Roger wrote as I replied before reading those posts. :)

[Jerry Peck]

2011 NEC
310.15 Ampacities for Conductors Rated 0–2000 Volts
(A) General.

(2) Selection of Ampacity. Where more than one ampacity
applies for a given circuit length, the lowest value shall be
used.
Exception: Where two different ampacities apply to adjacent
portions of a circuit, the higher ampacity shall be permitted to
be used beyond the point of transition, a distance equal to 3.0
m (10 ft) or 10 percent of the circuit length figured at the
higher ampacity, whichever is less.



This is a part of NEC code that I agree leaves you with a lot of imagination to work with ....:)

I've never used that code section in residential but my read of the exception is it targets single circuits that only have TWO ampacity considerations. I would also think that you couldn't consider any circuit serving general purpose receptacles. A likely place to use it would be a HVAC circuit to a roof top unit where you would have an adjustment for the new rooftop exposure multiples/rules. So the portion of the circuit on the roof top would have less ampacity than the portion of the circuit not on the rooftop.You could not consider IMO several (more than two) sections of changing ampacity.

I also do not think this exception gives permission to ignore bundling for NM or derating more than 3 ccc's in conduit not on a rooftop, I think it is speaking to single circuits to a known load.

I think this way becuase if you consider several circuits in conduit or bundled NM what are the odds that all the circuits are the same length to where you would be allowed to ignore bundling or derating for all of them.

But I confess I need to review this more as it is a section of code that I am not overly familiar.[/quote]

I agree with Roger, I believe this section was written for limited reasons and limited use, and Roger gave some good examples.

[H.G. Watson, Sr.]

...
What I'm most interested in is the reason for the exception.

...The engineer has tools availble for limiting available fault current, the most common being wire length. The impedance of a wire run means that the longer the run, the lower the availble fault current at the end of the wire...

There is also heat sink to consider...

[Kristi Silber]

...The engineer has tools availble for limiting available fault current, the most common being wire length. The impedance of a wire run means that the longer the run, the lower the availble fault current at the end of the wire...

There is also heat sink to consider...

Aha, I guessed right! See, I'm learnin'!

"Is it because on short stretches there's little impedance?" (post 69)

[Bill Kriegh]

Impedance is usually not an issue in residential wiring. Where it does become an issue is the service wires before the main disconnect/over current protection. There are thousands, sometimes tens of thousands of AMPs available and a fault can cause a spectacular show. For examples, enter "arcing" in the You Tube search engine. A few of these (sorry, don't keep a list) Power line arching and line failure - YouTube (http://www.youtube.com/watch?v=XV3ancFfPSQ&feature=related) show the electrical cables "jumping" around and indicate some of the reasons Watson gave for the wire nuts on the service being problematic in the event of a fault.

Having said that, high resistance connections in residential wiring are a common cause of burned devices and wiring, and a main reason connections are required to be in an enclosure.

A bit of looking around on various electrical forums will also yield pictures of rigid metal conduit where the sides are blown out when there was an internal fault.

[Roger Frazee]

Thanks to this forum I finally have to throw my 2008 in the trash from over use and abuse.... :) the binding has come apart so badly that I can no longer keep the pages in order.

Going to have to spring for a new one or get the electronic version. I am also going to Sams club and refresh my popcorn supply, though lately I've been reading most threads while swallowing chocolate m&m peanuts.

Getting back to the subject at hand. It really bugs me that the cmp cannot take just a second to correct the language on bundling or stacking nm cables. The real truth of the matter is bundling is becoming more of a concern and I'm reading in ECM that a new study is going to target this as the "possible" fire cause for several reported but unsolved home fires. I do not think it is debatable that bundling of NM is under the magnifying glass now and I would suspect that section of code will be clarified in the next code cycle or two.

I also am reasonably certain that the NEC when speaking of bundling of NM means to be tied together in some form or fashion. Lets say I bore a hole through a floor joist and run 5 12/2's thru it then thru the next joist and the next and so on. Obviously while going thru the holes they are going to touch, the only opportunity I have to maintain spacing is between joists. If I pull them tight then most likely they are all going to touch at some point between joists (may one won't but what are the odd's) .. there really is no certainty as to what spacing might result. I've never had this tagged as bundling or not maintaining spacing. Now I have had a few inspectors frown if I start tying those cables together with wire ties between the joists. It looks neat but IMO this is where you get into trouble with the NEC's use of the term bundling. That is a specific term used in the english language and it means to tie together or wrap up... like in a 'bundle'. Stacking is another term used in the NEC and just as undefined as bundling.

You simply cannot maintain spacing when spanning joists and I don't think you can stack .. you can however bundle to where there is virtually no spacing between cables.

So In my opinion unless you use some method of tying or wrapping those nm cables for a length of 24 inches they are not bundled.

Now as for not being able to enforce the definition "bundled" in any other article outside of 520 is hard for me to swallow. I'll bet my lucky star that the cmp meant bundled in article 310 to be the same term as in 520. When the term is used in 520's language it is used in the same context as 310 and clearly is meant to imply the concern on reducing a conductors ampacity ... if bundled.

So it's my opinion that at this point in time the NEC has not been clear on the intent of the bundling concept and as a result bundling can be anything from several cables very close together (sometimes touching) for 24 inches or to be tied together and touching the continuous 24 inches.

Now if they had said ' bunched ' things would be crystal clear to this old wireman ....;).

[Richard D. Fornataro]

Okay, had a little time to review the posts regarding the ad nausea commentary regarding “bundling.”

I normally am not blessed with the ancillary time necessary to provide such a detailed commentary so after a long holiday weekend, this is what I have come up with.

First let’s begin with the fact that the term “bundling” does not exist in the NEC.

Let’s assume that the entire dissertation stems from 310.15(B)(2)(a) which states: “ Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer that 600mm (24”) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a).”

All references are from the 2008 NEC which is the currently accepted reference in New York state.

NM cables are rated for residential branch circuits per 334.8 which refers one to 310.15 where Table 310.16 reflects the 60◦C (140◦F) conductor temperature rating.

It goes on further to state language very similar to 310.15(B)(2)(a), “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).” Exception shall not apply. The last paragraph that immediately follows states: “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 with310.15(B)(2)(a).

So…..would everyone agree that unless it meets the bolded, italic phrases in the above code references, THERE IS NO ADJUSTMENT FACTOR TO BE APPLIED. Get it? No fire- or draft stopped using thermal insulation, caulk or sealing foam means NO ADJUSTMENT FACTOR. No same opening in wood framing……NO ADJUSTMENT FACTOR!

The explanation provided in the handbook which is not enforceable as code language does indeed mention “bundling or stacking.” It also states “can” result in overheating.

There is no definition of “maintaining spacing.”

If it is so important, then why not define it?

Therefore, in conclusion, NM cables running parallel, adjacent or any other term describing that which others are referring to as “bundling” are NOT subject to derating unless they travel through the same opening in wood framing AND are fire- or draft stopped using thermal insulation, caulk or sealing foam.

Additionally, if one were to utilize the calculations posted by others in this forum, which were indeed mathematically correct, except for the interchanging of Fahrenheit and Celsius scales, electrical contractors would be wiring with #6 NM cable to meet the adjustment factors shown.

(I’ve never encountered “a t ypical 125◦C degree attic.”)

90◦C is 194◦F

Most attics I've encountered do not exceed 194F.


That’s the temperature that would be used during derating of NM cable

I’ve never seen anyone derate that way.

I’ve never seen a fire resulting from “bundling” as was originally described by the OP.


And in my jurisdiction, I AM THE AHJ and I read the code through to the end.


I don’t stop when I get an answer that supports my point of view.


I don’t pontificate about information obtained through casual conversation with engineers at manufacturing entities.

Code councils are apprised of many talented and learned professionals that author such.

I surmise that if this topic was so important, the ambiguity associated with the term “maintaining spacing” would be identified.


How does one “maintain spacing” of cable through a hole?


Is there a product available to facilitate such?

Anyone who still NEEDS to argue the point, put in a code suggestion for the next council to define “spacing.”

To all, I apologize for the protracted nature of this post.


I hope everyone enjoys a safe and Happy Holiday.

[Raymond Wand]

Richard,

Thank you. It makes perfect sense to me.

Further the research paper indicated succinctly that the problem of bundling does occur where wires are run through holes and foam, caulk are provided there is a increase in temps of the wire.

[Jerry Peck]

There is no definition of “maintaining spacing.”

If it is so important, then why not define it?

I started to put in a code change for a definition to define it, but realized that the deadline for code change proposals for the 2014 NEC had just passed (on November 4), so I will put a proposal in for the 2017 NEC.


And in my jurisdiction, I AM THE AHJ and I read the code through to the end.

Same in my jurisdiction. And derating has been enforced in South Florida where I used to be by those jurisdictions.

Derating is in the NEC for a reason, just like AFCIs are in the code for a reason. You may disagree with both of these, some do, but they are both in the code.

[Richard D. Fornataro]

I started to put in a code change for a definition to define it, but realized that the deadline for code change proposals for the 2014 NEC had just passed (on November 4), so I will put a proposal in for the 2017 NEC.



Same in my jurisdiction. And derating has been enforced in South Florida where I used to be by those jurisdictions.

Derating is in the NEC for a reason, just like AFCIs are in the code for a reason. You may disagree with both of these, some do, but they are both in the code.

Jerry,

I commend your effort to make defining "spacing" part of the Code. I hope to see it in the next cycle.

I sincerely hope that you got the part about NOT derating unless the applicable conditions were met for such.

Oddly enough, I fought that fight on a new hotel where NM was used as allowed and got over-ruled on the derating aspect where the installation involved several NM cables passing through wooden framing members with intumescing fire caulk installed in every hole.

The trite excuse used as a defense from the other side was that such was an "engineered solution" thereby nullifying my opinion.

I did want to convey the point however that maintaining spacing and derating is only applicable when in contact with insulation, caulk, etc.

The customary practice of bundling cables through basement joists, etc. is not a problem and should not be pointed out by HI's.

Of course, that's probably more prevalent here in the North where we routinely encounter basements in residential construction.

[H.G. Watson, Sr.]

2009 IRC

SECTION E3705 CONDUCTOR SIZING AND OVERCURRENT PROTECTION

E3705.1 General. Ampacities for conductors shall be determined based in accordance with Table E3705.1 and Sections E3705.2and E3705.3.




E3705.3 Adjustment factor for conductor proximity. 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 for distances greater than 24 inches (610 mm) without maintaining spacing and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table E3705.3.

Exceptions:

1. Adjustment factors shall not apply to conductors in nipples having a length not exceeding 24 inches (610 mm).
2. Adjustment factors shall not apply to underground conductors entering or leaving an outdoor trench if those conductors have physical protection in the form of rigid metal conduit, intermediate metal conduit, or rigid nonmetallic conduit having a length not exceeding 10 feet (3048 mm) and the number of conductors does not exceed four.

3. Adjustment factors shall not apply to type AC cable or to type MC cable without an overall outer jacket meeting all of the following conditions:
3.1. Each cable has not more than three current-carrying conductors.


3.2. The conductors are 12 AWG copper.


3.3. Not more than 20 current-carrying conductors are bundled, stacked or supported on bridle rings. A 60 percent adjustment factor shall be applied where the current-carrying conductors in such cables exceed 20 and the cables are stacked or bundled for distances greater than 24 inches (610 mm) without maintaining spacing

Type NM cable is not used at 90 degrees C but at 60 degrees C. The uncorrected, unadjusted ambient temperature for use of same is 30 degrees C ( 86 degrees F).

Show me an unconditioned attic that never exceeds 86 degrees F .



E3904.3 Securing and supporting. Raceways, cable assemblies, boxes, cabinets and fittings shall be securely fastened in place.



E3904.3.1 Prohibited means of support. Cable wiring methods shall not be used as a means of support for other cables, raceways and nonelectrical equipment.



The CMPs and the NEC has already addressed. The concept of thermal conductivity was ascribed earlier.




Article 310
Conductors for General Wiring

310.2 Definitions.

Thermal Resistivity. As used in this Code, the heat transfer capability through a substance by conduction. It is the reciprocal of thermal conductivity and is designated Rho and expressed in units degrees-C-cm/W.

310.15 Ampacities for Conductors Rated 0-2000 Volts

(A) General.
(3) Temperature Limitation of Conductors. No conductor shall be used in such a manner that its operating temperature exceeds that designated for the type of insulated conductor involved. In no case shall conductors be associated together in such a way, with respect to type of circuit, the wiring method employed, or the number of conductors, that the limiting temperature of any conductor is exceeded.
Informational Note No. 1: The temperature rating of a conductor (see Table 310.104(A) and Table 310.104(C) is the maximumtemperature, at any location along its length, that the conductor can withstand over a prolonged time period without serious degradation. The allowable ampacity tables, the ampacity tables of Article 310 and the ampacity tables of Informative Annex B, the ambient temperature correction factors in 310.15(B)(2), and the notes to the tables provide guidance for coordinating conductor sizes, types, allowable ampacities, ampacities, ambient temperatures, and number of associated conductors. The principal determinants of operating temperature are as follows:
(1) Ambient temperature -- ambient temperature may vary along the conductor length as well as from time to time.


(2) Heat generated internally in the conductor as the result of load current flow, including fundamental and harmonic currents.


(3) The rate at which generated heat dissipates into the ambient medium. Thermal insulation that covers or surrounds conductors affects the rate of heat dissipation.


(4) Adjacent load-carrying conductors -- adjacent conductors have the dual effect of raising the ambient temperature and impeding heat dissipation.
Informational Note No. 2: Refer to 110.14(C) for the temperature limitation of terminations.

(B) Tables. Ampacities for conductors rated 0 to 2000 volts shall be as specified in the Allowable Ampacity Table 310.15(B)(16) through Table 310.15(B)(19), and Ampacity Table 310.15(B)(20) and Table 310.15(B)(21) as modified by 310.15(B)(1) through (B)(7).


The temperature correction and adjustment factors shall be permitted to be applied to the ampacity for the temperature rating of the conductor, if the corrected and adjusted ampacity does not exceed the ampacity for the temperature rating of the termination in accordance with the provisiions of 110.14(C).
(3) Adjustment Factors.
(a) More than Three Current-Carrying Conductors in a Raceway or Cable. Where the number of current-carring conductors in a raceway or cable exceeds three, 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, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(3)(a). Each current-carrying conductor of a paralled set of conductors shall be counted as a current-carrying conductor.




The communications cable in parallel and zip tied with other systems and cables is bundled. "bundled" is used in both the electrical chapters of the IRC and in the NEC.

The NM installed through the floor support members is not bundled. There are a host of issues and concerns regarding the OP.

The subsequent photos and questions raised by others are addressed above and by other posts previously by myself and others.

Pinching NM under a staple or cable tie, impinging, restricting, compressing the individual conductor(s) insulation , has been a known "issue" for decades and the cause of fires. Similarly known has been the ability of PVC jackets to TRAP heat, nylon and similar, etc.

[H.G. Watson, Sr.]

...



I did want to convey the point however that maintaining spacing and derating is only applicable when in contact with insulation, caulk, etc.

...

Untrue.

[H.G. Watson, Sr.]

...
...(I’ve never encountered “a t ypical 125◦C degree attic.”)

90◦C is 194◦F

Most attics I've encountered do not exceed 194F.


That’s the temperature that would be used during derating of NM cable

I’ve never seen anyone derate that way.

I’ve never seen a fire resulting from “bundling” as was originally described by the OP.


And in my jurisdiction, I AM THE AHJ and I read the code through to the end.


...


ambient temperature correction factors apply at/kickin above 86F (30C).

NM Cable itself limited to use at 60C ampacity.

Openings in wood blocked/stopped in caulk or foam are NOT the only instances in which adjustments must be considered. Heat from adjacent NM cables (or other cables with a coating impeding heat transfer to free air) in contact for more than 24 continuous inches and not within a raceway are considered.

[Richard D. Fornataro]

Untrue.

For the love of God.....read 310.15(B)(2)(a) all the way to the end.

Don't quote code and cut it off where it suits your argument.

“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).” Exception shall not apply. The last paragraph that immediately follows states: “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 with310.15(B)(2)(a).

Does IRC 2009 differ from NEC 2008?

What are you not getting out of the above quoted?

New York State Residential Code does not contain reference to E3705.3 Adjustment factor for conductor proximity.

It does however state at the beginning of the Part VIII - Electrical Chapter that "This Electrical Part is a compilation of provisions extracted from the 2008 edition of the NEC."

If NEC and IRC differ....we have no disagreement, however: I am compelled to enforce the requirements of 2008 NEC and have stated such above .

That which is bolded or enlarged is so that you might actually peruse such.

You can't possibly argue with a direct quote from the accepted reference manual enforced by the state within which I endeavor.

As to the temperature rating of NM cable.

NM cable around here is imprinted with a 90 degree C (194 degree F) temperature rating.

Despite your protracted display of superfluous electrical code, once again you're quoting from the wrong book.

NEC 2008

334.80 Ampacity

"The ampacity of types NM, NMC and NMS cable shall be determined in accordance with 310.15. The amapacity shall be in accordance with the 60 degree C (140 degree F) conductor temperature rating. The 90 degree C (194 degree F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated capacity does not exceed that for a 60 degree C (140 degree F) rated conductor. The ampacity for types NM, NMC and NMS cable installed in cable tray shall be determined in accordance with 392.11.

That means that what I previously submitted was correct as written.

I can perceive that you are obviously an intelligent individual, however; in my short time perusing this forum, I have observed that you prefer to argue for the mere sake of arguing.

And....when you are wrong, peoples estimation of your contributions become degraded.

Other than that, I'm sure that you are genuinely concerned with the topics displayed in this forum.

Your propensity for pontificating in less than correct perceptions of code is deleterious to inexperienced individuals seeking expertise on a given topic.

Let's try to baffle observers of this forum with brilliance......not BS.

[Beverly Cofield]

The bundling of cables should be avoided due to the possibility of the cables overheating in this situation. The NEC 310.15(3)(B)(3) addresses this as to installed without maintaining spacing for 2’ or more, derating factors should be used. The number of conductors passing through one hole is not addressed. ROMEX® is a registered trademark of Southwire Company. You will find more information about ROMEX® brand cable at www.southwire.com/residential/romex.htm (http://www.southwire.com/residential/romex.htm)

This communication is for general informational purposes only and is not intended to constitute advice. As all the facts and circumstances in any given situation may not be apparent, this communication is not intended to be, and should not be, relied upon by the reader in making decisions with respect to the issues discussed herein, and the reader assumes the risk if he or she chooses to do so. The reader is encouraged to consult an expert before making any decisions or taking any action concerning the matters in this communication. All warranties, express or implied, including warranties regarding accuracy, adequacy, completeness, legality, reliability, safety or usefulness of any information, ARE DISCLAIMED. Southwire Company is not liable for any damages however caused and on any theory of liability arising in any way out of the information provided or the reader's use of it.

ROMEX® Cable Fan

[Robert Meier]

The bundling of cables should be avoided due to the possibility of the cables overheating in this situation. The NEC 310.15(3)(B)(3) addresses this as to installed without maintaining spacing for 2’ or more, derating factors should be used. The number of conductors passing through one hole is not addressed. ROMEX® is a registered trademark of Southwire Company. You will find more information about ROMEX® brand cable at Romex ® - Southwire: The Official Home of Romex ® Wire (http://www.southwire.com/residential/romex.htm)

This communication is for general informational purposes only and is not intended to constitute advice. As all the facts and circumstances in any given situation may not be apparent, this communication is not intended to be, and should not be, relied upon by the reader in making decisions with respect to the issues discussed herein, and the reader assumes the risk if he or she chooses to do so. The reader is encouraged to consult an expert before making any decisions or taking any action concerning the matters in this communication. All warranties, express or implied, including warranties regarding accuracy, adequacy, completeness, legality, reliability, safety or usefulness of any information, ARE DISCLAIMED. Southwire Company is not liable for any damages however caused and on any theory of liability arising in any way out of the information provided or the reader's use of it.

ROMEX® Cable Fan

Do you work for Southwire?

[Jerry Peck]

The number of conductors passing through one hole is not addressed.

Actually it is addressed (under certain conditions) and is not allowed, not without derating.

- 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).

[Robert Meier]

Actually it is addressed (under certain conditions) and is not allowed, not without derating.

- 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).

You wouldn't need to derate for only two cables even if you had 4 CCC's. :)

[Jerry Peck]

You wouldn't need to derate for only two cables even if you had 4 CCC's. :)

Did you read the bold part? :p

"Where more than two NM cables containing two or more current-carrying conductors"

2 + 2 = 4

And the 24" does not apply.

If that described condition exists through a single top plate of 1-1/2" ... and there are "more than two NM cables containing two or more current-carrying conductors" ... you gotta derate them suckers. :cool:

And don't forget, if those go into the attic, you gotta derate for ambient attic too (I usually recommend derating for ambient first, that let's you know how many current carrying conductors you can have without maintaining spacing - and 4 is too many for normal derating conditions, but here, for this specific conditions, 4 is okay).

[Robert Meier]

Did you read the bold part? :p

"Where more than two NM cables containing two or more current-carrying conductors"

2 + 2 = 4

And the 24" does not apply.

If that described condition exists through a single top plate of 1-1/2" ... and there are "more than two NM cables containing two or more current-carrying conductors" ... you gotta derate them suckers. :cool:

And don't forget, if those go into the attic, you gotta derate for ambient attic too (I usually recommend derating for ambient first, that let's you know how many current carrying conductors you can have without maintaining spacing - and 4 is too many for normal derating conditions, but here, for this specific conditions, 4 is okay).


Yes it says more than 2 cables. Meaning two cables, even with 6 CCC's do not require derating when installed in a fire or draft stopped hole.

[H.G. Watson, Sr.]

Peck and Fortunato,

You're NOT PAYING ATTENTION.

2011 does not read the same as 2008.

Retorting with selective quotes from a different edition of the NEC is frankly stupid.

You both lament earlier in this topic thread/discussion about submitting changes for a future edition, yet both fail to recognize when participants reference (frankly in response to your 2008 lamentations) with 2011 code language.

I identified what I quoted as 2011, (DUH! DIFFERENT TABLE NUMBERS~)

Peck, responding to Beverly Cofield citing 2011 language with 2008 language was typical for you, oversight, lazy and stupid.

The entire world is not frozen in time with your outdated 2008, many jurisdictions already use 2011; A Home Inspector should be aware of the CURRENT EDITIONS of the SAFETY CODES regarding BUILDING and PROPERTY MAINTENANCE CODES, etc. Not BACKWARDS IN TIME TO A LESSER 'used to be good enough' standard.

[Jerry Peck]

Yes it says more than 2 cables. Meaning two cables, even with 6 CCC's do not require derating when installed in a fire or draft stopped hole.

Robert,

You really do need to learn to read better.

I will repost the code to see if you can read it, to help you in your reading I will break some sentences up for your understanding:
- 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).

Okay, let us now count the number of conductors in
more than two NM cables
containing two or more
current-carrying conductors


more than 2 cables (count them: one ... two ... stop counting)
2 conductors in each cable (could be 3, but the minimum works out well here for your reading improvement)

Okay, 2 cables with 2 conductors in each is 4 conductors ... and that IS OKAY in this instance.

Okay, now follow closely here ... MORE THAN 2 cables, means at least 3 cables, and with 2 conductors in each is 6 conductors ... and that IS NOT OKAY in this instance.

Get it?

4 conductors in 2 cables with 2 conductors in each cable IS OKAY and derating IS NOT required.
6 conductors in 3 cables with 2 conductors in each cable IS NOT OKAY and derating IS required.

Not sure what is so difficult to understand about that ... well, maybe I do understand what may be so difficult - you do not seem to be able to separate the DIFFERENT requirement for derating for more than 3 conductors for more than 24 inches from more than 2 cables with 2 conductors in each cable, foamed/sealed around for as little as 1-1/2".

[Jerry Peck]

You're NOT PAYING ATTENTION.

2011 does not read the same as 2008.

Watson,

You are the one in your own time zone.

Most jurisdictions are still using the 2008, so the 2008 is the most common reference. By the way, there is VERY LITTLE change in that code section (334.80)

Just like most jurisdictions are still using the 2006 ICC codes, thus the most common reference is from the 2006 ICC codes.

SOME jurisdictions keep up to the minute on code cycle adoptions, alas, it would be nice if all adopted up to the minute code revisions (it would be scary if they did, but nice) - but that is in your dreams ... I'm talking real world here, not in your fantasyland mind.

[H.G. Watson, Sr.]

I did want to convey the point however that maintaining spacing and derating is only applicable when in contact with insulation, caulk, etc.



R.F.:


Again, UNTRUE! i.e. your use of the word "ONLY"

Maintaining spacing and derating IS applicable when in contact continuously for more than 24 inches, was the example given.

What about the entirety of 310 and 334 can't you retain?



Peck:

BAH, HUMBUG. You're tiny corner might be stuck in 2006 IRC and 2008 NEC, the WORLD ACCORDING TO PECK!!??

CODE ENFORCEMENT IS NOT WHAT THIS SITE IS ABOUT, NEITHER IS "HOME INSPECTION"!!!

Over the years on this site ("inspectionnews.net") and the now archived ("inspectionnews.com") you've gone on and on about inspecting to the LATEST, SAFEST edition of whatever code as a REFERENCE for HOME INSPECTION relative to SAFETY issues and what to make reference to regarding a home inspection (not necessarily call "deficient").

The model codes do NOT have a habit of (not intentionally, at least) of falling backwards on the issue of safety, and most certainly not the NEC, which unlike the I-codes are ANSI standard and not so easily politically or singular "interest group" skewed.

If an HI is going to make a "call" regarding an observed less than safe situation, it matters NOT what code edition JERRY PECK is doing code enforcement with.

The later editions of the National Electrical Code, NFPA 70 are modified also by the CHANGES in the STANDARDS that the equipment itself is made - and incorporate SAME (harmonize) regarding SAFETY issues and requirements.

Peck both YOU and R.F. carried on about your efforts to enhance the code and submissions.

The rest of the country isn't frozen in the 2008, and frankly some jurisdictions are using earlier versions. Few jurisdictions use any edition of the NEC withOUT ammendments.

You TWO brought up 2011 and 2014.

Spend a few bucks since you're so inclined to cut and paste wildly. The IDEA that you' had been THINKING about making a submission for 2014 when you can't grasp 2011 (or read for that matter) is frankly, typical, obvious also neither of you keeps up on the White Books, Marking Guides, or changes to the UL Standards for electrical equipment.

Someone recently posted to this thread today, a pause since Nov last year - you (in your usual manner) had to hit every thread active for the last four hours. You vomited 2008 up to someone who posted 2011 references from the manufacturer of "Romex".

[Robert Meier]

You wouldn't need to derate for only two cables even if you had 4 CCC's. :)


Yes it says more than 2 cables. Meaning two cables, even with 6 CCC's do not require derating when installed in a fire or draft stopped hole.


Robert,

You really do need to learn to read better.


Okay, let us now count the number of conductors in
more than two NM cables
containing two or more
current-carrying conductors


more than 2 cables (count them: one ... two ... stop counting)
2 conductors in each cable (could be 3, but the minimum works out well here for your reading improvement)

Okay, 2 cables with 2 conductors in each is 4 conductors ... and that IS OKAY in this instance.

Okay, now follow closely here ... MORE THAN 2 cables, means at least 3 cables, and with 2 conductors in each is 6 conductors ... and that IS NOT OKAY in this instance.

Get it?

4 conductors in 2 cables with 2 conductors in each cable IS OKAY and derating IS NOT required.
6 conductors in 3 cables with 2 conductors in each cable IS NOT OKAY and derating IS required.



Jerry, you're the one who needs to slow down and read what I wrote. I think that Watson and Fornataro have your panties all up in a bunch and you're not correctly reading my posts.

I said TWO NM cables, regardless of how many CCC's are in those cables, do not require derating in a sealed hole. I wrote one sentence so I'm unsure why you're so confused. I said TWO cables. :eek:

You can apologize now. :)

[Bill Kriegh]

Cables in fire stopped holes or in contact with thermal insulation---

I'm pretty much interested in knowing why this gets to be such an issue. Two cables with 2 or more conductors can be, for example, a 14-2 and a 14-2, a 14-2 and a 14-3, a 14-3 and a 14-3, a 14-2 and a 14-2-2, a 14-3 and a 14-2-2, or a 14-2-2 and a 14-2-2. Some enterprising individual could make 14-2-2-2-2-2 and the same rules would apply, as now written.

Now, with all 14-2s we have 2 circuits. With the other combinations we have either 3 or 4 circuits.

Other than code wording that says I have to derate more than 2 cables with 2 or more conductors (without maintaining spacing - whatever that is), somebody want to explain the major fire hazard where it's OK to have 4 circuits in 2 multi-conductor cables in the same fire stopped hole not spaced but not to have 4 two wire cables in the same fire stopped hole not spaced? Or, why, somehow, heat dissipation is different between the two situations?

Or do we assume the CMP is somehow ignorant of 14-3 and 14-2-2 cable and they "meant" for the article to mean 2 circuits (4 current carrying wires)?

How many read 334.80 and come away thinking you can only run two cables through a fire stopped hole without derating? Not what it says. So the next issue is do we now start seeing an insert for drilled holes to be fire stopped that maintains "spacing". Does that "spacing" get to be 1/6", 1/8"? How about just inserting wood wedges into the hole between cables before caulking or foaming? How many NM-B cables in a 2 inch fire stopped hole with shims installed? Spacing is maintained.

There's a lot of things in the NEC not to like. One of them is, and continues to be, that without clarification IN WRITING supplied with cable or defined in the NEC, "spacing" continues to mean "doesn't touch" That's just as solid a definition as the one that says that a load that is turned off no less often than every 2 hours 59 minutes and 59 seconds isn't a continuous load, even if after that second it is turned back on again for 2 hours 59 minutes and 59 seconds - but is written as "A load where the maximum current is expected to continue for 3 hours or more. Means the same thing. Practical? Meet code intent? Dunno. Does that 1 second make a real difference?

Frankly, from my experience, we'd be better served if receptacles and switches were required to be the "back wire" type and beeped incessantly till properly torqued. I've seen many more fires started from improperly installed devices and splices - stuff that, incidentally, almost never gets inspected, than NM-B cables installed as shown in the OPs picture( none, so far) - which, by the way are NOT bundled and maintain "some" spacing over a 2 foot length.

[Robert Meier]

Cables in fire stopped holes or in contact with thermal insulation---

I'm pretty much interested in knowing why this gets to be such an issue. Two cables with 2 or more conductors can be, for example, a 14-2 and a 14-2, a 14-2 and a 14-3, a 14-3 and a 14-3, a 14-2 and a 14-2-2, a 14-3 and a 14-2-2, or a 14-2-2 and a 14-2-2. Some enterprising individual could make 14-2-2-2-2-2 and the same rules would apply, as now written.

Now, with all 14-2s we have 2 circuits. With the other combinations we have either 3 or 4 circuits.

Other than code wording that says I have to derate more than 2 cables with 2 or more conductors (without maintaining spacing - whatever that is), somebody want to explain the major fire hazard where it's OK to have 4 circuits in 2 multi-conductor cables in the same fire stopped hole not spaced but not to have 4 two wire cables in the same fire stopped hole not spaced? Or, why, somehow, heat dissipation is different between the two situations?

Or do we assume the CMP is somehow ignorant of 14-3 and 14-2-2 cable and they "meant" for the article to mean 2 circuits (4 current carrying wires)?


In the worst case scenario of off the shelf NM cable, with 2-12/2/2 NM cables in the fire or draft stopped hole you would have 8 CCC's. If you did apply derating to this worst case scernario then you would have a derating factor of 70%. So 30 amps * 70% would give you 21 amps which is still good on a 20 amp OCPD. Whether or not the CMP was cognizant of this fact when they added this to the NEC I don't know.

[Jerry Peck]

Jerry, you're the one who needs to slow down and read what I wrote.

I said TWO NM cables, regardless of how many CCC's are in those cables, do not require derating in a sealed hole.

Yes sir ... :o ... that is what you said.


You can apologize now. :)

I do need to slow down and read better ... I do hereby extend my apology to you ... along with my typing hand so you can slap it. :)

[Jerry Peck]

So 30 amps * 70% would give you 21 amps which is still good on a 20 amp OCPD.

Unless those same conductors ran into the typical ventilated attic, in which case those cables would also need to be derated for ambient temperature.

start with your 21 amps and derate to 71% for a typical attic, that derated ampacity is now only 14.91 amps ... not good enough for even a 15 amp circuit.

"Close" to good enough for a 15 amp circuit, but "close" only counts in horse shoes, hand grenades, and atom bombs. ;) (Given in the order of 'how close' "close" needs to be. :)

[Robert Meier]

Yes sir ... :o ... that is what you said.



I do need to slow down and read better ... I do hereby extend my apology to you ... along with my typing hand so you can slap it. :)

No problem Jerry we're all here have a discussion and to share ideas.
I was confused because almost all of your posts are right on target. :D

[Jerry Peck]

I'm pretty much interested in knowing why this gets to be such an issue.

They were doing testing on this for some time, some of the testing was in the IAEI News a few years back.

The testing revealed serious overheating at those locations.

[Bill Kriegh]

It's probably going to take more than a straight face during an explanation to convince me that 4 circuits in 2 14-2-2 cables don't have the same issues (or lack of them) that 4 14-2 cables have in the same fire stopped hole.

[Jerry Peck]

It's probably going to take more than a straight face during an explanation to convince me that 4 circuits in 2 14-2-2 cables don't have the same issues (or lack of them) that 4 14-2 cables have in the same fire stopped hole.

I would not even attempt to try to convince my 6 year-old granddaughter of the above.

I believe ... yes, I believe ... the intent was in reference to 4 conductors as in 2- 12-2 or 14-2 NM cables. And not necessarily to 12-2-2 NM cables because 12-2-2 cables *already* require derating simply by being 12-2-2 and having 4 current carrying conductors within the same cable. If those cables are *already* required to be derated in 310.15(B)(2):
- (2) 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 installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a). Each current-carrying conductor of a paralleled set of conductors shall be counted as a current-carrying conductor.
- - - FPN No. 1: See Annex B, Table B.310.11, for adjustment factors for more than three current-carrying conductors in a raceway or cable with load diversity.
- - - FPN No. 2: See 366.23(A) for adjustment factors for conductors in sheet metal auxiliary gutters and 376.22(B) for adjustment factors for conductors in metal wireways.
- - - Exception No. 1: Where conductors of different systems, as provided in 300.3, are installed in a common raceway or cable, the derating factors shown in Table 310.15(B)(2)(a) shall apply only to the number of power and lighting conductors (Articles 210, 215, 220, and 230).
- - - Exception No. 2: For conductors installed in cable trays, the provisions of 392.11 shall apply.
- - - Exception No. 3: Derating factors shall not apply to conductors in nipples having a length not exceeding 600 mm (24 in.).
- - - Exception No. 4: Derating factors shall not apply to underground conductors entering or leaving an outdoor trench if those conductors have physical protection in the form of rigid metal conduit, intermediate metal conduit, or rigid nonmetallic conduit having a length not exceeding 3.05 m (10 ft) and if the number of conductors does not exceed four.
- - - Exception No. 5: Adjustment factors shall not apply to Type AC cable or to Type MC cable without an overall outer jacket under the following conditions:
- - - - (1) Each cable has not more than three current-carrying conductors.
- - - - (2) The conductors are 12 AWG copper.
- - - - (3) Not more than 20 current-carrying conductors are bundled, stacked, or supported on “bridle rings.”
- - - - - A 60 percent adjustment factor shall be applied where the current-carrying conductors in these cables that are stacked or bundled longer than 600 mm (24 in.) without maintaining spacing exceeds 20.

Being as 12-2-2 is already derated ... why derate it again for the same reason (yes, it would still require derating for ambient if the cables went into the typical vented attic which gets quite hot, but not if they went into a sealed attic with spray foam insulation on the underside of the roof deck).

[Robert Meier]

I would not even attempt to try to convince my 6 year-old granddaughter of the above.

I believe ... yes, I believe ... the intent was in reference to 4 conductors as in 2- 12-2 or 14-2 NM cables. And not necessarily to 12-2-2 NM cables because 12-2-2 cables *already* require derating simply by being 12-2-2 and having 4 current carrying conductors within the same cable. If those cables are *already* required to be derated in 310.15(B)(2):

Being as 12-2-2 is already derated ... why derate it again for the same reason (yes, it would still require derating for ambient if the cables went into the typical vented attic which gets quite hot, but not if they went into a sealed attic with spray foam insulation on the underside of the roof deck).

Excellent point about the 4 wire cables already requiring derating for the 4 CCC's in the cable. :cool:

So the only scenario left that muddies the waters is two 3-wire cables which could be 4, 5 or 6 CCC's and derating would not apply in the sealed hole.

[Jerry Peck]

Excellent point about the 4 wire cables already requiring derating for the 4 CCC's in the cable. :cool:

So the only scenario left that muddies the waters is two 3-wire cables which could be 4, 5 or 6 CCC's and derating would not apply in the sealed hole.

Robert,

Same section applies to that the same way:
- a) If the 3-wire is a MWBC, then there are only 2 current carrying conductors, which means it is no different than 2-wire NM with regard to derating.
- b) If there are 3 current carrying conductors in that 3-wire cable, then where it the neutral for the other hot conductor ... unless it is a switch leg run to a combination switch switch receptacle outlet which is supplied with a hot-neutral-switch leg from a lighting outlet box which is supplied with a hot-neutral. The switch leg is carrying the same current as the hot until a load is placed on the receptacle outlet (this is one example of what could be wired with that 3-wire and have 3 current carrying conductors).

Most likely, with 2 3-wire NM cables, you would have only two current carrying conductors in each cable, and only 4 current conductors in those two NM cables - this would be the most likely scenario.

In b) above you could have 5 or 6 current carrying conductors if you wired two separate combination switches that way and ran both NM cables through the same hole in the top plate. This would be highly unlikely, I would suggest.

[Robert Meier]

Robert,

Same section applies to that the same way:
- a) If the 3-wire is a MWBC, then there are only 2 current carrying conductors, which means it is no different than 2-wire NM with regard to derating.
- b) If there are 3 current carrying conductors in that 3-wire cable, then where it the neutral for the other hot conductor ... unless it is a switch leg run to a combination switch switch receptacle outlet which is supplied with a hot-neutral-switch leg from a lighting outlet box which is supplied with a hot-neutral. The switch leg is carrying the same current as the hot until a load is placed on the receptacle outlet (this is one example of what could be wired with that 3-wire and have 3 current carrying conductors).

Most likely, with 2 3-wire NM cables, you would have only two current carrying conductors in each cable, and only 4 current conductors in those two NM cables - this would be the most likely scenario.

In b) above you could have 5 or 6 current carrying conductors if you wired two separate combination switches that way and ran both NM cables through the same hole in the top plate. This would be highly unlikely, I would suggest.

Yup, the switch leg scenario was exactly what I was thinking.

[Richard D. Fornataro]

Per Peck and possibly Watson who just can't seem to spell a persons name correctly, we should be wiring all houses with #6 NM cable after all their deratings are applied for "bundling, temperature, etc."

I'd be curious to hear from any electrical contractors whom have been subjected to what I consider this type of unreasonable demands as it regards "bundling derating and temperature derating."

The pictures that started this thread, albeit a little sloppy, would not be subject to derating by any inspector in my area and again, if applied per the above scenarios, #6 NM cable would be required.

Talk about driving up the cost of construction!:confused:

[Stuart Brooks]

For a change of pace - I almost fell over when I saw this installation. It's very rare in this area to see something done this well. The electrician actually plastic standoffs to maintain spacing between cables. It may look like the cables are together but there is around 1/4" between each. Okay, a little closer between standoffs due to cable sag.

[Jerry Peck]

Stuart,

Make sure they fireblock those open gaps at the top of the wall in the first photo where the concealed spaces between the studs communicate with the space above.

[Erik Pendleton]

9 two-conductor cables means 18 current carrying conductors, and 10-20 current carrying conductors is derated to 50%.

12 NMB is derated from 30 amps and 14 NMB is derated from 20 amps, so, presuming no derating for ambient temperature (i.e., not in an attic for example), 12 NMB would have a 15 amp rating (not suitable for anything greater than a 15 amp breaker) and 14 NMB would have a 10 amp rating (not suitable for anything at all basically).

Now, if *any portion* of the any one of those circuits goes through an attic, than that entire circuit also needs to be derated for ambient temperature, and if we presume a typical 125 degree attic, the derate rating is further derated to 76%, which would make 12 NMB derated to 11.6 amps (not suitable for anything at all basically), and 14 NMB derated to 7.6 amps (making it a wasted used of copper not suitable for anything).

And, if the attic temperature is higher than 131 degree (and up to 140 degrees) the ambient derating factor is 0.71 instead of 0.76, and if the attic temperatures reach 141 degrees to 158 degrees, the derating factor is 0.58.

What really kills bundling and lack of maintaining space is having to derate for ambient *and* more than 3 conductors, derating for more than 3 conductors is bad enough.

This doesn't seem right. The bundling and ambient are not in the same area. If they were bundled in the attic, I would agree. If the derating instances are in separate areas, it makes sense to use the full ampacity to derate each instance, and go with the resulting lowest amapacity.

Or is there a reference that says that all derating instances are cumulative? What if a wire went to the attic for 10 ft, returned to conditioned space for 10ft and then returned to the attic for 10ft? Would you derate it twice? Or if it were bundled for 3ft, unbundled for 50ft then rebundled for 3ft? Would you derate it twice?

Doesn't seem logical.

[Roland Miller]

If the conductors are both bundled and run through a high ambient temperature, the NEC requires both adjustments be made for those conductors affected. If part of the conductors only are bundled or are only ran through a higher temperature, only that single adjustment needs to be made. Both conditions add heat to the conductor as does the current flow. Since we are protecting the insulation (which is temperature rated and the weak link, usually) all adjustments need to be applied that the conductor is exposed to. There is not one specific statement that states this and that is one reason why the NEC is NOT a training manual..The other things to consider are the temperature limitations of the terminations, splices, raceway, etc..

[Erik Pendleton]

If the conductors are both bundled and run through a high ambient temperature, the NEC requires both adjustments be made for those conductors affected. If part of the conductors only are bundled or are only ran through a higher temperature, only that single adjustment needs to be made. Both conditions add heat to the conductor as does the current flow. Since we are protecting the insulation (which is temperature rated and the weak link, usually) all adjustments need to be applied that the conductor is exposed to. There is not one specific statement that states this and that is one reason why the NEC is NOT a training manual..The other things to consider are the temperature limitations of the terminations, splices, raceway, etc..


I just don't buy that. Bundling causes localized heating. If a bundle of wires heats, the effects of that heat won't be carried to a remote location and other local effects remote from the bundle won't affect the bundle either.

Without some definitive guidance on this I would say that combining localized adjustments is wrong.

[Erik Pendleton]

In fact from the NEC:

"Exception: Where two different ampacities apply to adjacent portions of a circuit, the higher ampacity shall be permitted to be used beyond the point of transition, a distance equal to 3.0 m (10 ft) or 10 percent of the circuit length figured at the higher ampacity, whichever is less."

To me this says after 10 ft the limit is no longer cumulative. Agreed?

[Roland Miller]

In fact from the NEC:

"Exception: Where two different ampacities apply to adjacent portions of a circuit, the higher ampacity shall be permitted to be used beyond the point of transition, a distance equal to 3.0 m (10 ft) or 10 percent of the circuit length figured at the higher ampacity, whichever is less."

To me this says after 10 ft the limit is no longer cumulative. Agreed?


This exception applies when the termination temperature limitation is lower then the ampacity of the conductor. When this occurs, after 10 feet you can use the higher ampacity of the conductor. So NO I don't agree. This is why it is not a training manual..

[Erik Pendleton]

This exception applies when the termination temperature limitation is lower then the ampacity of the conductor. When this occurs, after 10 feet you can use the higher ampacity of the conductor. So NO I don't agree. This is why it is not a training manual..

"310.15 Ampacities for Conductors Rated 0–2000 Volts .15 Ampacities for Conductors Rated 0–2000 Volts.
(A) General General.
(1) Tables or Engineering Supervision. Ampacities for conductors shall be permitted to be determined by tables as provided in 310.15(B) or under engineering supervision, as provided in 310.15(C).
FPN No. 1: Ampacities provided by this section do not take voltage drop into consideration. See 210.19(A), FPN No. 4, for branch circuits and 215.2(A), FPN No. 2, for feeders.
FPN No. 2: For the allowable ampacities of Type MTW wire, see Table 13.5.1 in NFPA 79-2007, Electrical Standard for Industrial Machinery.
(2) Selection of Ampacity. Where more than one calculated or tabulated ampacity could apply for a given circuit length, the lowest value shall be used.
Exception: Where two different ampacities apply to adjacent portions of a circuit, the higher ampacity shall be permitted to be used beyond the point of transition, a distance equal to 3.0 m (10 ft) or 10 percent of the circuit length figured at the higher ampacity, whichever is less."

I think you are wrong.

[Roland Miller]

Erik--post some examples and show us how it works. I think you will find your assumption won't hold up..

[Erik Pendleton]

Erik--post some examples and show us how it works. I think you will find your assumption won't hold up..

I think I already did........

Bundled wires in basement for 3 feet. One of those wires then travels through the house, say 30 feet to attic with 130F ambient.

My understanding is that these two adjustment issues should be considered individually as the bundle in the basement will not impact the temperature 30 ft away. Therefore derate based on one factor, the one that is most severe.

If the bundle were in the attic, then you would have to derate for both factors.

[Roland Miller]

https://www.youtube.com/watch?v=7kU0VJhwtzs

You are stretching the application of this article. Your example is deficient. Heat does transfer to other parts of the circuit (is not localized).

[Erik Pendleton]

https://www.youtube.com/watch?v=7kU0VJhwtzs

You are stretching the application of this article. Your example is deficient. Heat does transfer to other parts of the circuit (is not localized).

Really? You propose that video as support for your opinion?

That video doesn't address this issue at all so if that is the best you can come up with, then I am more certain you are wrong.

[Roland Miller]

Really? You propose that video as support for your opinion?

That video doesn't address this issue at all so if that is the best you can come up with, then I am more certain you are wrong.

If the conductors are both bundled and run through a high ambient temperature, the NEC requires both adjustments be made for those conductors affected. If part of the conductors only are bundled or are only ran through a higher temperature, only that single adjustment needs to be made. Both conditions add heat to the conductor as does the current flow. Since we are protecting the insulation (which is temperature rated and the weak link, usually) all adjustments need to be applied that the conductor is exposed to. There is not one specific statement that states this and that is one reason why the NEC is NOT a training manual..The other things to consider are the temperature limitations of the terminations, splices, raceway, etc..

I don't believe you even read what I posted because you decided I disagree with you. Since you don't have the ability to discern meaning from the written word or even a video that applies, why would I think you can read the NEC and get anything but more questions. Then argue about something you don't know much about.

Try re-reading what I said. Maybe consult an english/grammar expert and then see how it applies to you question.

My statement is code correct as written.

[Roland Miller]

(2) Selection of Ampacity. Where more than one ampacity
applies for a given circuit length, the lowest value shall be
used.(2014 NEC)

This is all you need to know. The exception does not apply to your question.

[Erik Pendleton]

(2) Selection of Ampacity. Where more than one ampacity
applies for a given circuit length, the lowest value shall be
used.(2014 NEC)

This is all you need to know. The exception does not apply to your question.

I apologize - I read your comments as disagreeing with me (particularly where you said give an example and my logic wouldn't hold up).

But now I see you seem to be agreeing with me:

The lowest ampacity value is to be used. So if as in my example, 3 ampacities apply (ignoring termination constraints for this example): 1. bundle adjusted for the bundled portion, 2. unadjusted for unbundled portion in normal temperature (basically the living space of the house), and 3. ambient temp adjusted for the high ambient of the attic run.

Per your NEC quote above, the lowest ampacity of the 3 should be applied to all of the circuit.

This makes sense and is the position I was advocating.

If the bundle were in the attic - then you would have to apply both factors to that portion of the circuit and apply that much lower ampacity to the entire circuit.

This also makes sense and is also the position I was advocating.

Again, I apologize if you were agreeing with the entire time. Forum communications are sometimes not as clear as we believe. Sometimes it is better to preface a statement with "Yes, you are correct" or "No, that is incorrect".

Thanks

[Roland Miller]

I apologize - I read your comments as disagreeing with me (particularly where you said give an example and my logic wouldn't hold up).

But now I see you seem to be agreeing with me:

The lowest ampacity value is to be used. So if as in my example, 3 ampacities apply (ignoring termination constraints for this example): 1. bundle adjusted for the bundled portion, 2. unadjusted for unbundled portion in normal temperature (basically the living space of the house), and 3. ambient temp adjusted for the high ambient of the attic run.

Per your NEC quote above, the lowest ampacity of the 3 should be applied to all of the circuit.

This makes sense and is the position I was advocating.

If the bundle were in the attic - then you would have to apply both factors to that portion of the circuit and apply that much lower ampacity to the entire circuit.

This also makes sense and is also the position I was advocating.

Again, I apologize if you were agreeing with the entire time. Forum communications are sometimes not as clear as we believe. Sometimes it is better to preface a statement with "Yes, you are correct" or "No, that is incorrect".

Thanks

Apology accepted. I also apologize for my sometimes abrupt and abrasive postings. Yes--you have it the way I would apply the NEC. I didn't say Yes or No because I was not sure of your position since you asked me to post the code reference. Sometimes people sign up and ask the "loaded" questions to further pursue a disagreement outside the forum.

OBTW--welcome to this forum. You will find some of us (me included) have strong opinions.;) Hopefully you will find things to add and have the staying power to keep posting..