12-3 for outlets?

He or she probably intended to share a neutral to run 2 circuits to the addition. This is OK as long as they are on opposite legs at the service panel. It sounds like you need someone who is qualified to check this out.

I have come in "second hand" on jobs and it took me awhile to figure out what the original sparky was planning.

No offense to you, but you need help here.

PARENOS said:

Is is bad practice to just wire in one of the hots on a single pole and leave the other hot in the box, I really do not want to go this way.

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It wouldn't hurt anything as long as you cap off the extra hot wire. But if it bothers you, just disconnect the other end from its breaker... if it's actually connected already. Not entirely clear from your description.

ETA: It could be as simple as he just ran out of 12/2, and had enough 12/3 to get the job done, never intending to use the extra conductor. It happens...

Just do a split receptacle and you won't be doing what you didn't want to do.

Break off the little tab, put the red on one outlet and the black on the other.

:laughing:

p.s. whenever fishing wires to remote spots on the home we usually bring a spare anyway. doesn't hurt anything and sure makes things easier if someone changes their mind about something after you're done fishing and pulling for wires...

PARENOS said:

I am doing a attic conversion and have ran into a 12-3 that was run by an electrician that started the job but is to booked up and she can not get back. Being that i thought everything was hooked up and all it would be was some outlets and lights, I told her that I could handle that. The electrician ran a 12-3 upstairs for the outlets, I believe he did this so he could branch out with the other live wire for any future outlets, however the panel box is 100 and there is only one more circuit open to wire in this 12-3. Is is bad practice to just wire in one of the hots on a single pole and leave the other hot in the box, I really do not want to go this way. I would appreciate any ideas

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I would call the original electrician and see what they had in mind.

Jim

PARENOS said:

I am doing a attic conversion and have ran into a 12-3 that was run by an electrician that started the job but is to booked up and she can not get back. Being that i thought everything was hooked up and all it would be was some outlets and lights, I told her that I could handle that. The electrician ran a 12-3 upstairs for the outlets, I believe he did this so he could branch out with the other live wire for any future outlets, however the panel box is 100 and there is only one more circuit open to wire in this 12-3. Is is bad practice to just wire in one of the hots on a single pole and leave the other hot in the box, I really do not want to go this way. I would appreciate any ideas

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Why would the second one "red wire" be hot ? Just leave each end unhooked & capped off............

Hire a sparky unless you have an electrical license.

I have seen 12-3 used to feed outlets off two breakers with a shared neutral and always felt like that was wrong. Lets say they use space heaters/window ac units in a couple spots fed by this split 12-3, even if they are on the the two seperate circuits they still share the same neutral, and the combined load could very easily exceed the 20A current carrying capacity of a single 12 thhn.

Now since there is no current limiting device on the neutral over time the extra amps(aka heat) would eventually cause a insulation failure. Am I completely off base here, if so please enlighten me. It just seems like its a shortcut to avoid having to fish two wires instead of one.

jarhead0531 said:

Hire a sparky unless you have an electrical license

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Because you said this, you are absolved for your other error!

jarhead0531 said:

I have seen 12-3 used to feed outlets off two breakers with a shared neutral and always felt like that was wrong. Lets say they use space heaters/window ac units in a couple spots fed by this split 12-3, even if they are on the the two seperate circuits they still share the same neutral, and the combined load could very easily exceed the 20A current carrying capacity of a single 12 thhn.

Now since there is no current limiting device on the neutral over time the extra amps(aka heat) would eventually cause a insulation failure. Am I completely off base here, if so please enlighten me. It just seems like its a shortcut to avoid having to fish two wires instead of one.

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When two hots (or three in the case of a three-phase system) from seperate poles feed a shared neutral, the loads "cancell out", and the neutral only carries a small unshared load. Done properly, there is no danger in overloading the neutral.

Done improperly, the whole house could burn down

The 12-3 from the panel to the first recepticle would be the feed, the Electrician most likely ran 3 wire for a second feed if needed. If the 12-3 is ran from recepticle to recepticle then i would believe it is for switched recepticles, black being the full time feed and the red being switched. I run 3-wire to hard to get locations in a home when pulling circuits such as an attic space or a basement/crawl space and there are one or two finished living spaces in between.

jarhead0531 said:

Hire a sparky unless you have an electrical license.

I have seen 12-3 used to feed outlets off two breakers with a shared neutral and always felt like that was wrong. Lets say they use space heaters/window ac units in a couple spots fed by this split 12-3, even if they are on the the two seperate circuits they still share the same neutral, and the combined load could very easily exceed the 20A current carrying capacity of a single 12 thhn.

Now since there is no current limiting device on the neutral over time the extra amps(aka heat) would eventually cause a insulation failure. Am I completely off base here, if so please enlighten me. It just seems like its a shortcut to avoid having to fish two wires instead of one.

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No, the load on the neutral is not the sum of the hots, but the difference between the hots. Each leg is 180 degrees out of phase with the other.

480sparky said:

1. Who wires attics with 12 THHN?
2. The ampacity of 12 THHN is 30, not 20.

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Just curious, are you serious?

I thought it was more:
14awg - 15 amps
12awg - 20/21 amps
10awg - 30/33 amps

Of course, I don't even know what THHN means. :laughing:

boman47k said:

Just curious, are you serious?

I thought it was more:
14awg - 15 amps
12awg - 20/21 amps
10awg - 30/33 amps

Of course, I don't even know what THHN means. :laughing:

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THHN is the type of covering (insulation) on the wire.

If you have a code book, check out table 310.16. There are lot's of variables.