Yep, you're right. I have a better diagram in my Code application,
but it's more work to get it online, so I took the - surprise! - lazy
way out and posted a link that answered Mike's question. I'll try to
get a more definitive diagram posted.
Woot! Even better, I just found the 2009 IRC online. Here's the
pertinent page in glorious full color black and white:
No mention of prohibiting holes at any point along the joist. That is
odd, as I do remember seeing such a restriction somewhere. Here's
another, more specific diagram from Bloomington, IN, but still no
restriction on drilling near the joist bearing points:
Here's the main IRC page. Bookmark 'em, Danno!
The best place for holes in a joist is at the neutral axis where the
joist is only stressed in bending. What this means in practice is to
stay away (maybe 2 feet?) from the bearing points (over and under wall
framing) and then to put your holes in the middle of the joist.
Yes, in fact if you would find it easier, you can feed all four 12/2s,
or two 12/3s, without any problem NEC-wise.
The maximum size hole you are allowed to drill is quite a bit more
than what you will need, e.g. a 1.25" hole for 4 12/2s would be fine.
The running of multiple cables through the same holes can cause
derating problems. Two 12/3WG cables is only four current carrying
conductors. The THHN conductors used in modern day Non Metallic
Cable, Type NMC, has an ampacity of thirty amperes; even though the
code will not let you use it at more than twenty amperes for most
loads. So you can run four of the 12/2WG, 12/3WG or two of the 12/4WG
cables through the same holes without any problem. If you run cables
having a total of ten or more current carrying conductors through the
same holes the ampacity of the twelve gauge cables drops under twenty
amperes to fifteen amperes, fifty percent, of the THHN conductor's
maximum rated ampacity.
Or hazard to people working on it in the future. I got knocked on my
ass because someone way back used a common nuetral on separate
circuits. White wire bit me - I traced it to a yard light that was
In that case there should have been at least 2 hot wires in the box, one
of which remained hot when you killed the circuit you were working on.
"Hot neutrals" are the reason the 2008 NEC was changed to require listed
handle ties or multipole breakers.
Ok, thanks again. Lets add more to this now that I uncovered
The present stove is on a 40A circuit. I was told newer stoves require
a 60A circuit.
Which means now I have to run a new 6/3 with a ground.
How many holes or notches are you permitted to drill through one
joist? Is it better to drill several small holes , or one big hole?
Avoid notches whenever possible - far more problematic. Your one big
hole wouldn't be that big of a hole. If the one hole falls within the
guidelines in that link I posted, you're fine. You won't be anywhere
near the upper limit of allowable hole size, so I'm not quite sure why
you're worrying. If you want to drill more holes that's not a problem
unless you drill them to close together.
I don't know anything about electric stoves. But NM (Romex or SER)
#6 Cu has an ampacity of only 55 amps. Which means you can use a 60A
breaker on it only if the load is rated at 55A or lower. If the stove
is rated 60A, you need to use #4 Cu.
I remeber reading that if curent to/from device is in one conduit, the
EMF will not create induction heating. But your case will because at
least one of your wires is sending in one conduit, and the return is
in the other. I'm sure the bonafide electricians out there will
Having a physical current loop will cause EMI and induction heating in
any ferrous metal encircled by the loop. However, using a 12/3 cable
for a MWBC does not create a current loop, all the conductors are
routed together in the same cable.
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