Replacing 12/2 with 12/3 behind wall

iya

Hi all. I want to replace a 12/2 running behind my wall to a 12/3.. I know it goes through one stud, but I don't know how big a hole was drilled in there. The idea of "fishing" is daunting to me, so I guess my question is, would it be possible to tape the end of the new 12/3 to the end of the old 12/2, and then pull it through, so the new one would take the old one's place?

I'm trying to do this without having to take sections of my wall out :P

Jim Port

Generally cables are required to be secured within 8-12" of the box. When run parallel to studs no more than 4'-6" between staples.

I don't think using the old cable as a pull string will work for you.

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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.

iya

Thanks for the quick reply, Jim Port. I guess I'll have to put more thought into this, then.

Jim Port

You might be able to pull the baseboard and notch the drywall and then drill your holes.

You also might be able to go down and then back up if you have access below the floor.

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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.

iya

Actually, this is what I'm trying to do.. The disposal unit is hardwired. It's one 12/2 straight from the switch on the wall to the upper left side of the sink, went down, then through a stud, to the right basin where the unit is attached. I want to get this set-up:


thus the replacing 12/2 with a 12/3..
I've considered just using one of those.. raceways? Like the molding things.. to cover outside-wall wiring, but I don't know how acceptable that would be in the kitchen..

Jim Port

Does the switch box have the to white connected together? If so you could run a two wire cable from the switch box to the DW.

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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.

AllanJ

Cables fished through walls or ceilings do not have to be fastened to studs, etc.

The old 12-2 cable installed before the drywall was put on will have been fastened to the studs and therefore could not be used as a pull string for the 12-3 cable.

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iya

Jim Port - Actually, yes - at the switchbox, the grounds and whites are pigtailed, while the blacks are on the switch. I suppose that IS the easiest way to do it - just wire the DW separately.

AllanJ - if I do not have to fasten to studs, do I at least have to secure them to the box itself?

Another question - The house was built in `72; could the receptacle box used then possibly not have prepunched knockout holes? I wasn't able to see any, but it could just be that it was pretty.. rusty.. in there. That's what made me think of replacing the 12/2 with 12/3 - i won't need new holes It was pretty solid-looking metal to me, so without those prepunched KOs, I'd need some good muscle to start another one for new wires.

Jim Port

The knockout should be punched. You would just need to pry or push the tab out of the hole.

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Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.