Max # of Romex in wood holes

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Strombea

Strombea

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Prescott, Arizona, USA
This may have been Beaten to death but my inspector is saying that 334.80 doesn't allow more than 4 romex wires (8 ccc) in the same hole. Obviously a lot of us used to drill a 2 inch hole through the too plate to put home runs in panel. I guess this would be against code. 90 degree column derating only allows for up to 9 ccc in a hole and still have good ampacity.

my question is in the term "properly spaced" and what does that mean because we definitely spread them out ASAP on each side of hole.
 
Go down two thirds of the page and read your article

2020 NEC FAQ's

Is pretwisting conductors required when using wirenuts? This question is not answered in the NEC, it is a product listing question. Products are required to be used in accordance with their listing by 110.3(B). Most (if not all) wirenuts are listed for use as follows: Pretwisting the...
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Strombea said:
This may have been Beaten to death but my inspector is saying that 334.80 doesn't allow more than 4 romex wires (8 ccc) in the same hole. Obviously a lot of us used to drill a 2 inch hole through the too plate to put home runs in panel. I guess this would be against code. 90 degree column derating only allows for up to 9 ccc in a hole and still have good ampacity.

my question is in the term "properly spaced" and what does that mean because we definitely spread them out ASAP on each side of hole.
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If the hole is not fire stopped or draft stopped there is no limit as to how many cables can be in the hole. If it is then derating applies but that still does not limit the number of cables within the filled hole it only requires that the ampacity of the cables be adjusted.
 
infinity said:
If the hole is not fire stopped or draft stopped there is no limit as to how many cables can be in the hole. If it is then derating applies but that still does not limit the number of cables within the filled hole it only requires that the ampacity of the cables be adjusted.
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yet that we can use sch 40, and stuff away, derating be d*mned via 312.5C ex questions 334.80's rationale Infinity

~RJ~
 
When the hole is stuffed with fire or draft stopping and more than 2 NM cables are installed derating is required because when tested in a lab it was found that the temperature rating of the conductors could be exceeded. IMO it will never happen in the real world.
 
infinity said:
When the hole is stuffed with fire or draft stopping and more than 2 NM cables are installed derating is required because when tested in a lab it was found that the temperature rating of the conductors could be exceeded. IMO it will never happen in the real world.
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Does fire or draft stopping include the spray foam that every hole must be filled with? I guess we will start to see this more often where I'm at as there is no way around the code.
 
Strombea said:
Does fire or draft stopping include the spray foam that every hole must be filled with? I guess we will start to see this more often where I'm at as there is no way around the code.
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Yes but do horizontal holes in wood also get filled?
 
No it's only the top plates for draft stop to the attic and it's only above the panel that this ever comes up

however now with everyone spray foaming the attic for insulation you would think that the top plates don't need it any more but I guess draft stop is different than insulation.
 
We've been required to have fire stop also in horizontal wall at 10 ft intervals. Premise is the that it will limit spread to within section with each section requirement of 1 hr burn.
 
It seems to me that if one has drilled a 2" hole in a wood top plate and put say 16 CCCs in Romex through it, there should be an appropriate divider that can be added to the hole to separate the cables into 2 groups of 8 CCCs The divider would "maintain spacing" between the groups so that 334.80 paragraph 2 would apply to each group separately once the hole is firestopped.

As to the details of what spacer would be sufficient, that is subject to debate. I would argue for anything that provided, say, 1/4" separation between the groups. Which would include putting 8 CCCs on one side of the hole and 8 CCCs on the other side of the hole, with just firestopping foam maintaining separation.

But perhaps that's entirely too reasonable. : - )

Cheers, Wayne
 
infinity said:
When the hole is stuffed with fire or draft stopping and more than 2 NM cables are installed derating is required because when tested in a lab it was found that the temperature rating of the conductors could be exceeded. IMO it will never happen in the real world.
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So does it occur to you the inequity of derating throughout the code might be considerate of nrtl's that exist in the real world infinity?

~RJ~
 
I get the idea of heat dissipation and proper spacing, with foam being a deterrent to such.

If I saw 35 home runs all laying in a budle for a length of 40 feet, and it all got foamed in, I'm on board for sure.

But I have an impossible time believing 4 cables through 2 top plates and a nailer (4-1/2 inches) is enough to create a "house fire" hot spot.
 
James L said:
But I have an impossible time believing 4 cables through 2 top plates and a nailer (4-1/2 inches) is enough to create a "house fire" hot spot.
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Agree. Even the conductors would conduct and disperse heat away from the hole.

Instead of one 2" hole, how about two 1.5" holes?
 
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