We have ran into an issue pertaining to the amount of NM-B (Romex) a local inspector will allow to be installed within a drilled hole in a basement floor joist. To my knowledge, there is no code reference stating the maximum amount of wire allowed to be ran through a bored hole that is not fire caulked or sealed. He is referring to Table 310.15 (B)(3)(a). If there is no limitation as per the total number of conductors that can be installed within a bored hole, would he be referring to this section because the total length of conductors exceeds 24"? If that is a legitimate argument, how are stack staples UL listed and sold for that exact use? Any insight or help would be greatly appreciated!
2017 NEC, NM-B THROUGH BORED HOLES IN WOOD
- Thread starter gasgas
- Start date
- Status
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Imo, if you have a number of cables thru bored holes running for a distance of 2' or more then it is bundling as the wires will lay atop of one another. Other inspector may not see it that way.
I believe the stackers have some info warning that a local jurisdiction may have a problem with their use.
I believe the stackers have some info warning that a local jurisdiction may have a problem with their use.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
You are correct about the hole in the wood, there is no ampacity adjustment required if you stuff 20 cables into a hole with no fire or draft stop material. The question is are the cables that are run together between the joists bundled. IMO unless they physically tied together with something like a zip tie they are not "bundled". The NEC needs to clarify this.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
If you bore a bunch of holes in the ceiling joists then how would it be possible for the cables to not be laying atop of one another?
A zip tie only ties them together at the spot where the zip tie is installed. I would not call that bundled for more than 24".
Over the years I required a lot of folks to cut away the zip ties on "bundled" Romex but it's difficult for me to get too concerned when you look at the actual current being carried by most Romex cables in residential applications
- Location
- New Jersey
- Occupation
- Journeyman Electrician
There are still spaces between the cables for heat dissipation. If you bundle them together then you have removed the spaces between the cables. Like Augie stated when they're zip tied they're bundled and the air spaces between the cables are eliminated.
I'll bet that no one has ever seen a bunch of cables run through holes in wood where heat damaged the cables.
- Location
- Bremerton, Washington
It’s not often we see a moderator only response
PaulMmn
Senior Member
- Location
- Union, KY, USA
- Occupation
- EIT - Engineer in Training, Lafayette College
Fill a hole? Hah! In the house -I- bought, Uncle Fred didn't fill a hole-- he drilled a ROW of holes! Maybe an inch or two between them! One Romex (sometimes 2) per hole. At least a dozen holes. In at least 3 joists! There's a wooden post under the joist holding up the refrigerator.
Is the floor insulated? If not the joist would need to be 25" thick before you have an issue. I had an inspector make me fan out the NM between joist bays once, one big hole and lots of NM in it running through the building.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Purely as a devil's advocate, the language in 310.15(B)(3)(a) is "installed without maintaining spacing," which could be argued as requiring some positive measure be taken to maintain spacing.
In practice I agree with you.
Cheers, Wayne
- Location
- New Jersey
- Occupation
- Journeyman Electrician
IMO another poorly worded code section. Ambiguity should be the enemy of the NEC but it isn't. I'll stick with my opinion that if they're not physically bundled then there is space between the cables and at the end of the day they'll never overheat anyway.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
We will have to agree to disagree. I can't see how there is space between the cables when they are run horizontally thru holes. the cables are basically laying on each other. A zip tie-- where????
I used them in an attic. I ran about 20 homeruns across the attic and zip tied them every 4' or so. In between the ties the nm cables were spread apart so I don't see that as bundling. An inspector turned me down so I asked him directly about drilling 2" holes between ceiling joist and running cables thru it. He said that was fine, then he looked at me and said "I see what you mean." We always allowed it but that is really bundled. I smiled.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Bundled is defined by the NEC in Article 100 so that's not relevant if there are no zip tie. So it comes down to what "maintaining spacing for a continuous length longer than 600 mm (24 in.)" means. I'm of the opinion that air gaps will exist between the cables if they're not bundled so there is no portion that is a continuous length greater than 24". Personally with #14 and #12 conductors I would probably just put 4 cables in each hole.
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This picture was taken of a passing job using the Arlington speedway. There seems to be a double standard, considering we fail a job for having 5 wires running in parallel together through bored holes, however the Arlington product is "listed for the use", not to mention the stackable staples.. We have been in business since 2006 and wired roughly 1,500 new homes, non of which have burnt down to date. Dozens of inspectors have inspected our work over the years and 95% of the homes completed have been wired within coded areas. This is the first time I have heard of an inspector only allowing two (2) wires per hole within a basement. Does it come down to the grey area of the NEC and AHJ? Keep in mind this is coming from the same inspector that refused to inspect a meter socket last winter because there was not a shoveled pathway through the 6" or so of snow..
Tulsa Electrician
Senior Member
- Location
- Tulsa
- Occupation
- Electrician
Picture 3354 is this code compliant?
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
How CCCs per hole? On the left, if that's (4) 12/2 NM, even if you treat them as bundled, they have an ampacity of 30A (90C ampacity) * 70% (8 CCCs) = 21A, so still fine on a 20A breaker.
On the right, if that's (2) 14/2, (1) 12/2, and (1) 10/3, then the #12 calc is the same as on the left. The #14 calc is 25A (90C ampacity) * 70% (8 CCCs) = 17.5A, so still fine on a 15A breaker. For the #10, the calc is 40A * 70% = 28A, still fine on a 30A breaker, but the load is limited to 28A.
That's just if you treat the cables in each hole as bundled, which is debatable. And of course if I've miscounted the cables from the picture, then the computations need adjusting.
I would say one way to ensure that they can't reasonably be seen as bundled would be to install some spacers/spreaders separating the cables in the middle of each joist bay. E.g. a small plywood disc with 4 (or more) slots spaced around the edge, one cable in each slot, with the disc just held by the cable tension. That would obviously count as "maintaining spacing."
Cheers, Wayne
On the right, if that's (2) 14/2, (1) 12/2, and (1) 10/3, then the #12 calc is the same as on the left. The #14 calc is 25A (90C ampacity) * 70% (8 CCCs) = 17.5A, so still fine on a 15A breaker. For the #10, the calc is 40A * 70% = 28A, still fine on a 30A breaker, but the load is limited to 28A.
That's just if you treat the cables in each hole as bundled, which is debatable. And of course if I've miscounted the cables from the picture, then the computations need adjusting.
I would say one way to ensure that they can't reasonably be seen as bundled would be to install some spacers/spreaders separating the cables in the middle of each joist bay. E.g. a small plywood disc with 4 (or more) slots spaced around the edge, one cable in each slot, with the disc just held by the cable tension. That would obviously count as "maintaining spacing."
Cheers, Wayne
According the the UL listing and the inspector, 3354 is code compliant.. If your not familiar with the product, there is a 3 sided covering that slides into the inside of the hangers as well, only allowing any "heat" to disapate from the top of the raceway. Doesn't make sense to us.
Tulsa Electrician
Senior Member
- Location
- Tulsa
- Occupation
- Electrician
I see, no I'm no familiar with that product. So it is a cable tray.
Thank you
Amps
Electrical Contractor
- Location
- New Jersey
- Occupation
- Electrical, Security, Networks and Everything Else.
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