Wiring a Split-Tab Receptacle
Use this technique to provide separate circuits from a single outlet.
Standard duplex receptacles have a small metal tab between the brass screw terminals. The tab conducts power to both terminals, even if you connect a hot wire to just one terminal. However, if you break off and remove the tab, you isolate the two terminals and create, in effect, two single receptacles—each of which requires a hot lead wire to supply power.
This technique, known as split-tab wiring, is often used to provide separate circuits from a single outlet, a configuration commonly used when connecting a disposal and a dishwasher. The disposal receptacle is almost always controlled by a switch, which allows you to turn off the disposal at another location. To supply two hot leads to a split-tab receptacle, electricians usually run a 12/3 or 14/3 cable.
To create a split-tab receptacle, use needle-nose pliers to twist off the small metal tab between the brass screws 1. Next, connect the bare ground wire to the green grounding screw on the device and connect the white neutral wire to a silver screw. If you keep a slight tension on the wires as you tighten each screw, they’ll be less likely to slip off 2.
Flip the receptacle over to expose the brass screws on the other side, and connect a hot lead to each brass screw. If you’re running 12/3 or 14/3 cable, one hot wire will typically be red and the other black 3. Finally, push the receptacle into the box, install the mounting screws, and apply the cover plate 4.
Although this 15-amp split-tab receptacle is fed with 12/3 cable (rated for 20 amps), there’s no danger of the load exceeding the rating of the receptacle. Because of the configuration of the slots, the receptacle can receive only a 15-amp plug.
Excerpted from Wiring Complete, 3rd Edition (The Taunton Press, 2017) by Michael Litchfield and Michael McAlister