how many cables allowed


Old 09-21-19, 04:57 PM
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how many cables allowed

I'm installing several new outlets in my sons new home they are moving into. One is behind the range which was electric but the previous owner installed a gas line and that is what my son has. However no electrical outlet was installed to power the clock and control lights. The previous owners just ran the stove plug up and to the side outlet at the counter. They also never had an above the range microwave, just a hard wired hood and vent fan. The outlet behind the stove was a no brainier. Installed and working. The microwave is a bit more of challenge, but I have it solved. I found a 20 amp unused circuit and will use that for the outlet installer in the upper cupboard.

My question...Is there any maximum (perhaps no more than 3 ) cables allowed to go through a single hole in the joist in the basement? I doubt it's a problem or code but I thought I would ask. I have several cables already running through the joist and I would hate to drill more holes. The existing ones all have two and could easily accommodate three.
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Old 09-21-19, 06:27 PM
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There is no hole size vs amount of cables rule. The cables should fit comfortably in the drilled hole.
Old 09-21-19, 06:32 PM
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No electrical rule. However there are structural rules for how big and where you can drill holes.
Old 09-23-19, 10:45 AM
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I agree, no electrical rules, but many years ago I had inspectors tell me that BOCA codes only allowed one cable per hole. Of course, no one was ever able to cite the code reference or show me the code. I really think it was just a preference of the chief inspector. In a case like that you just do what the inspector says.
Old 09-23-19, 01:51 PM
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There is no specific rule here about the hole.
That being said, there are rules about number of cables run together for more than a foot (3 cables) and conduit space usage couldn't be more than I believe 75% full.
Wouldn't be a bad guide to follow for joist holes despite there being no rule specifically.
Old 09-24-19, 06:37 PM
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There are two rules in play here:
1) 310.15(B)(3)(a) ...or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600 mm (24 in.) and are not installed in raceways

2) 334.80 ...where more than 2 NM cables are installed without spacing between cables through the same opening in wood framing that is to be sealed with insulation, foam or caulk...

If either above apply you are required to derate the cables. Same rule of thumb applies I have stated before. If you keep the current-carrying conductors to 9 or less, through a hole or raceway, then derating has no effect to 90 degre C conductors.
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