300.4 Bored holes # of wires per hole max hole size

[dm9289]

I was looking thru some residential videos of installs and inspections, i seen a couple things i had questions on that i could not resolve regarding bored holes and restrictions

1. Large home an individual neatly ran many NM cables at least 15 from what i could see thru 2-9/16" holes for many ceiling joists (looked like very long hallway) for a large home. The NM cables were not bundled with tie wraps between ceiling joists but all went thru many ceiling joists together, at least 10 that i can see he was very proud of the neatness and called attention to it.
Would this arrangement require the adjustment factors of 310.15(B)(3)(a) ?
Is there any max hole size? there was more than 1-1/4" of wood beyond holes


2. Another situation an individual said no more than NM cables in a bored hole. I could not find a code reference to support. Does anyone know where this limitation would be in code? If it exists?

3. the only limits I really seen involving bored holes were the 1-1/4" requirements of 300.4 is there any others you could point me to that I should be aware of?



Thanks as always for your input it is appreciated

 

[infinity]

There is no NEC limit as to the number of NM cables in a hole in wood. If there is a fire or draft stop material in the hole then derating applies but the NEC does not say that there is a specific limit as to the number of cables within the hole. So if I put 10 cables in a fire stopped hole where the proper derating has been factored in that would be code compliant.

 

[dm9289]

There is no NEC limit as to the number of NM cables in a hole in wood. If there is a fire or draft stop material in the hole then derating applies but the NEC does not say that there is a specific limit as to the number of cables within the hole. So if I put 10 cables in a fire stopped hole where the proper derating has been factored in that would be code co

There is no NEC limit as to the number of NM cables in a hole in wood. If there is a fire or draft stop material in the hole then derating applies but the NEC does not say that there is a specific limit as to the number of cables within the hole. So if I put 10 cables in a fire stopped hole where the proper derating has been factored in that would be code compliant.

My guess the hole size would be more of a building code inspector issue.

So you are saying the 15 NM cables going horizontally thru many the holes would not require ampacity adjustment assuming no fire stop

 

[LarryFine]

1. Large home an individual neatly ran many NM cables at least 15 from what i could see thru 2-9/16" holes for many ceiling joists (looked like very long hallway) for a large home.

Is that "two 9/16" holes?

 

[dm9289]

Is that "two 9/16" holes?

actually no one large hole of 2-9/16" thru a manufactured ceiling joist made up of 2 what appeared to be 2x4 with some form of OSB in the middle to simulate a beam

 

[wwhitney]

actually no one large hole of 2-9/16" thru a manufactured ceiling joist made up of 2 what appeared to be 2x4 with some form of OSB in the middle to simulate a beam

For solid sawn joists, the prescriptive hole size rule in the IRC/IBC is a hole diameter of no more than 1/3 of the joist height, and a location that leaves at least 2" of solid wood at the top and bottom of the joist, and 2" between holes. [Presumably if you could circumscribe 2 or more closer holes with one large circle that would meet the hole size and location restrictions, the closer holes would be OK.]

For I-joists like you describe, you need to find the joist make and model and check the manufacturer's literature. Often larger holes are allowed, although they may be prohibited in certain locations.

Cheers, Wayne

 

[dm9289]

For solid sawn joists, the prescriptive hole size rule in the IRC/IBC is a hole diameter of no more than 1/3 of the joist height, and a location that leaves at least 2" of solid wood at the top and bottom of the joist, and 2" between holes. [Presumably if you could circumscribe 2 or more closer holes with one large circle that would meet the hole size and location restrictions, the closer holes would be OK.]

For I-joists like you describe, you need to find the joist make and model and check the manufacturer's literature. Often larger holes are allowed, although they may be prohibited in certain locations.

Cheers, Wayne

Thank you for the references

 

[LarryFine]

Usually, I-joists are made with pre-punched knockouts in the web that you remove with a hammer.

 

[dm9289]

Usually, I-joists are made with pre-punched knockouts in the web that you remove with a hammer.

Now i have been looking for the NEC definition of maintaining spacing. In my way of thinking 10 NM cables going thru 16" on center floor joists are bundled or have no spacing, it seems like my opinion is in the minority

 

[infinity]

Now i have been looking for the NEC definition of maintaining spacing. In my way of thinking 10 NM cables going thru 16" on center floor joists are bundled or have no spacing, it seems like my opinion is in the minority

You're correct that in that scenario the NEC does not define those a bundled. It doesn't say that they're not bundled either. IMO since there are air gaps around the cables that they are not bundled so it comes down to a judgement call.