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.
Cheers, Wayne
GFCI receptacles only require a dedicated neutral downstream of the receptacle (on the load side), you can feed them with a shared neutral no problem.
Cheers, Wayne
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 always on.
Harry K
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 soemthing.
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.
R
very helpful diagram. Where it says 'no notches', does that mean no holes also? I'm thinking no it doesn't mean that, but wasn't sure.
ok, that clears that up. what i did is run 12/3 from box to box to box, and alternated using the red and black. In this case, i have to use a gfci at each and every box.
Rico-
Thanks, a great diagram.
I remember a while ago someone posted one similar but it also spoke to the prohibition of holes in the "bearing zone".
Something like "no holes within xx" of the end of the joist / beam" ? Bearing zone or shear zone? I dont remember the details & cannot find the thread or link.
cheers Bob
The reason why I prefer notches is because I have to break a sheetrock ceiling in a living room a few times to run the wires to the panel. Rather than cut several big holes in the sheetrock to drill through the floor joists, I thought just "notching" the sheetrock under where the joist is, then notchng the joist would be easier and less to patch up.
Maybe the existing 40A circuit I have for the stove is fine. I just went on GE's website and looked at the specs for their electric stoves, and they all say use 40A minimum circuit. They also say to use a 40A stove plug kit. So at least I don't have to re-run the circuit, which would have been a PITA.
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.
Cheers, Wayne
No notches applies to the central third of the joist. Holes are fine there.
Cheers, Wayne
I would think that staying a distance D (depth of member) away from the bearing zone would be sufficient, but I would stay 2D away to be sure.
Cheers, Wayne
Notching is much, much worse for the strength of the joist than drilling a hole at the centerline. A 2x8 notched 1" deep at the bottom has the same remaining depth as a 2x7, but only half the strength at that location. The corner of the notch creates a stress concentration and a place for a crack to start propagating.
Cheers, Wayne
No. Holes and notches are a bit different in their effects on stress concentration. Holes are less problematic (I'm trying really, really hard not to make some innuendo with that one!), so that's why I advise to avoid notching if at all possible.
R
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.
R
I'm not sure about your numbers, but yes, the notch reduces the overall strength whereas a hole usually does not.
R
The difference in patching a 2" x 2" hole in a drywalled ceiling is not all that much less than patching a 4" x 12" hole, and, like I mentioned earlier, you should avoid notching. Notching affects floor stiffness and deflection, holes don't.
You'd also be required to cover each notched wire crossing with a metal plate, and that can create a small lump in the ceiling. Maybe not a big deal, but you'd have to feather out the patch more than a flush patch.
BTW, my purpose here is not to always make less work for you, it's to help you to always do better work with the least amount of effort possible.
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