12-2 NM through a hole

[PapaC]

4-nm cables in a hole

4-nm cables in a hole

I see how we get to the limit of 4 NM Cables in a penetration and maintain our 20 amp rating on the cables. One remaining issue is the question of thermal foam in the hole. Isn't some form of foaming required in most cases by 300.21?

 

[PapaC]

12-NM through a hole

12-NM through a hole

Looks like 300.21 requires that holes through floors, ceilings, hollow spaces, and most places a circuit would run has to be sealed to reduce the spread of fire. I see that fire-resistant-rated walls is mentioned, but the list goes on from there. I think that holes must be filled, so we limit the ampacity of the cables as stated above.:-?

 

[stew]

foam or fire stop is only required where 300.21 says . it does not mention framing members at least not in the 2005. the openings referred to in 300.21 are thru fire rated walls,parttions floors or ceilings. our most common penetrations are thru framing members in wall studs and joists which are not covered in 300.21. Now that being said if the dang ol contarctor gives a laborer a bunch if insulation and says go plug up those holes then he just created maybe a bigger hazard to our properly installed cable right? not to mention now we have a possible code violation beacuse of derating eh?

 

[quogueelectric]

I believe building structural code

I believe building structural code

Does not allow for a bigger than 3/4" hole in a 2x4 and has limits of no drilling in the outer 2-3rds on either side only in the inner 1/3 of the stud and not in the outboard 1/3 of the length of a floor joist or ceiling rafter. Hardly anyone enforces these codes but if you insist on being a code hawk read them and weep you will never work again.