[Jeremy Hillary Boob PhD]

I've got an outlet (standard, 2 outlet thing, that is) behind my kitchen sink, and I want one of them (for garbage disposal) to be controlled by a switch and the other to be on all of the time. Can I use a single 12-3 romex instead of two 12-2 wires? That is, at the switch I will connect the red and black of the 12-3 to the incoming hot (black) wire. Then, say, the red wire will be used to connect the switch to one of the outlets, while the black will go to the "regular" (always-on) outlet. Then the white/neutral of the 12-3 will be connected to neutrals on both of the outlets. I hope this is reasonably clear...

Anyways, it seems to me that when the switch is "on", this setup would be the same as if I'd wired the outlets in the standard sort of way (i.e., no switch involved, and a single hot wire powering both outlets). Let me know if I've missed something here. Thanks.

 

[hayewe farm]

I've got an outlet (standard, 2 outlet thing, that is) behind my kitchen sink, and I want one of them (for garbage disposal) to be controlled by a switch and the other to be on all of the time. Can I use a single 12-3 romex instead of two 12-2 wires? That is, at the switch I will connect the red and black of the 12-3 to the incoming hot (black) wire. Then, say, the red wire will be used to connect the switch to one of the outlets, while the black will go to the "regular" (always-on) outlet. Then the white/neutral of the 12-3 will be connected to neutrals on both of the outlets. I hope this is reasonably clear...

Anyways, it seems to me that when the switch is "on", this setup would be the same as if I'd wired the outlets in the standard sort of way (i.e., no switch involved, and a single hot wire powering both outlets). Let me know if I've missed something here. Thanks.

A little confused, you have the red wire hooked to the hot, to the switch, and to the outlet.

What is already there, the outlet and the switch, or just and outlet and you are adding a switch? What is the existing wiring?

 

[joed]

Yes you can do that. It is the preferred way.

 

[Stubbie]

why is it the preferred way?

When power comes to the switch first then to the undersink receptacle it is the preferred way to split the receptacle for a switched outlet and a constant hot outlet by breaking the tab between the brass screws. The 12/3G allows for two hots ( one switched) and a single neutral at the receptacle.

 

[joed]

I think there is some code rule against running two cables between the same two boxes. Something about all conductors being in the same cable or raceway.

 

[hayewe farm]

I still say the OP did not supply enough information to answer his question.
If the receptacle is already in place and active and he wants to add a switch for half the receptacle he would only need 12/2.

If the power is to the outlet box and he has a switch that controls both halves he would only need to add a jumper.

If the power is to the switch and he wants to split the receptacle he would replace the 12/2 with 12/3.

Of course in all cases he would have the cut the hot jumper between the halves.

 

[SD515]

I think there is some code rule against running two cables between the same two boxes. Something about all conductors being in the same cable or raceway.

To my knowledge, no code against running 2 cables between the same 2 boxes. What you want to be aware of is that each cable is utilizing either a neutral (its proper one) or a swithed leg, (or a 240v type setup) so that the power is traveling in both directions in a cable at the exact same time, to minimize the induction imposed on the wires.

 

[Jeremy Hillary Boob PhD]

When power comes to the switch first then to the undersink receptacle it is the preferred way to split the receptacle for a switched outlet and a constant hot outlet by breaking the tab between the brass screws. The 12/3G allows for two hots ( one switched) and a single neutral at the receptacle.

Yes, this is exactly what is happening. Thanks to all for the info (and sorry I didn't respond sooner, but I was busy yesterday).