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The Answer. According to the National Electrical Code, you can have 4 12/2 nonmetallic sheathed cables through a single bored hole that is fire- or draft-stopped using thermal insulation, caulk, or sealing foam, or where proper spacing is not maintained for more that 24 in.
22 sty 2018 · The code doesn't directly address how many NM can be run through a bored hole. So, as many as can be installed without damage. As for derating, I would think the 24" or shorter sleeve requirement would apply.
8 mar 2012 · I need help finding exact code section stating number of NM cables allowed through bored/drilled hole, regarding derating. I thought I had come across a section stating this. I believe 2 were allowed before derating, something to do with insulation being installed in hole as well.
2 wrz 2003 · The bottom line is: Up to 4 cables may be pulled in bored holes for distances longer than 2 feet, shorter distances have no limits on the number of cables. The International Residential Code limits the size of bored holes in lumber.
22 lis 2022 · 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.
In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed through bored holes in joists, rafters, or wood members, holes shall be bored so that the edge of the hole is not less than 32 mm (1 1/4 in.) from the nearest edge of the wood member.
Smaller cables shall be run either through bored holes in joists or on running boards. Where run parallel with the framing member, the wiring shall be 1.25 inches from the edge of a framing member such as a joist, rafter or stud or shall be physically protected.
