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Discussion Starter #1
I am in the process of replacing a MWBC that ran through much of my house. I am replacing it with two separate AFCI protected circuits.

My question is if I run power to a switch, can I run a 12-3 cable from it to the box for the light fixture to continue the circuit down the line past the light?

My thought would be to pigtail the neutral in the box at the light and attach it to a 12-2 to continue the circuit on. I have never seen this done though. I can't see though why it wouldn't work.

How do you normally plan your circuits? Most of the wiring right now is ungrounded and in violation of box fill limits, but was done 60 years ago. I have been replacing as I go, but I have been going slow.

Also do you have any tricks for taking out old boxes to put larger ones in?

Thanks as always.
 

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I almost never run a feed to a light and continue to the next device.
I always run my feed to the switches and receptacles.

Feed switch 1, cable to light fixture, another cable to feed the next switch, and so on and so on.

Old boxes can be removed by cutting the nail with a hacksaw, pulling the box from the wall, or drop it into the wall.

Their are 2 types of old work boxes. One uses a set of wings to pull the box flat against the back of the sheetrock two uses screws mounted into the inside of the box that screws to the stud.

Both boxes have limitations for box fill, but both come in several sizes.
 

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Discussion Starter #3
what box will work for 12-2?

If I use a single gang box (3.5" deep) I am at 21 cu. in., with three 12-2 cables and a switch I would need 24.75", how would you make that work?

Thanks for the quick reply.
 

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What numbers did you use to do the calculations

3 cables = 7 wires. You only count the ground once+the device which counts twice.

Each wire counts as 2.25x7+15.75+device counts as 2(2.25)=4.5 for a total fill of 20.25, more than enough room for a 21 cu box.
 

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Master Electrician
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do wire nuts count in the U.S.
every 2 wire nuts counts as a conductor in canada and i was curious.
 

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