When you need a wall switch to control a lamp while keeping the bottom half of the receptacle live for a vacuum or phone charger, you are looking at wiring for a switched outlet. In the electrical trade, this is commonly called a "half-hot" or "split-wired" receptacle. While a fully switched outlet (where the switch kills power to both top and bottom sockets) is wired just like a standard light fixture, the half-hot configuration requires a specific 3-wire cable setup and a physical modification to the receptacle itself.
The direct answer for a modern, code-compliant half-hot installation is this: you need 14/3 or 12/3 NM-B cable, a standard 15A or 20A duplex receptacle, and you must physically break the brass connecting tab on the hot side of the device. Below is the exact bench-to-jobsite procedure to get it right the first time.
Tools, Materials, and Wire Sizing
Before opening any junction boxes, gather the correct materials. Using the wrong gauge or an improperly rated device is a leading cause of thermal degradation at the terminals.
Required Tools
- Voltage Tester: Non-contact voltage tester (NCVT) and a digital multimeter (CAT III or CAT IV rated).
- Wire Prep: Wire strippers (capable of stripping 12 and 14 AWG solid copper) and Lineman pliers.
- Drivers: #2 Robertson (square) and #2 Phillips screwdrivers. (Robertson is preferred for terminal screws to prevent cam-out).
- Receptacle: Standard 15A or 20A duplex receptacle (e.g., Leviton 5262 or Eaton TRCR15). Ensure it is a "break-off tab" style, which virtually all modern commercial and residential duplex receptacles are.
Wire Gauge and Device Rating Matrix
Your cable gauge must match the breaker protecting the circuit. Never put 14 AWG wire on a 20A breaker.
| Circuit Breaker | Cable Required (Half-Hot) | Cable Required (Fully Switched) | Receptacle Rating | Max Continuous Load |
|---|---|---|---|---|
| 15 Amp | 14/3 NM-B | 14/2 NM-B | 15A Duplex | 12 Amps (1440W) |
| 20 Amp | 12/3 NM-B | 12/2 NM-B | 20A Duplex | 16 Amps (1920W) |
Note: Modern NFPA NEC guidelines (Article 404.2(C)) require a neutral conductor at the switch box. This is why a /3 cable (Black, Red, White, Bare) is mandatory for new half-hot installations running from the switch to the outlet, replacing the older /2 "switch loop" method.
Critical Safety Protocol: De-Energize and Verify
Working on branch circuits involves 120V AC, which is lethal. You must follow the OSHA Test-Before-Touch protocol:
- Turn OFF the circuit breaker at the main panel. Apply a lockout/tagout device if others are in the home.
- Test your NCVT on a known live circuit (like a neighboring room) to verify the tester's battery is good.
- Scan the target outlet and switch box. The NCVT should remain silent.
- Remove the faceplate and test again directly against the exposed wire insulation and terminal screws.
- Use a multimeter set to VAC. Place one probe on the black wire and the other on the bare ground. The reading must be 0.0V.
Never assume a wire is dead based on the wall switch position or a tripped GFCI elsewhere in the house. Always verify with a meter.
Step-by-Step Wiring for a Half-Switched Outlet
This procedure assumes you are wiring the receptacle end of a 14/3 or 12/3 NM-B cable run that originates from the wall switch box. (At the switch box, the black wire connects to the switch's common/line terminal, the red wire connects to the load terminal, and the white wire is pigtailed into the neutral bundle to satisfy code).
- Prepare the Receptacle and Break the Tab: Hold the receptacle face-up. Look at the side with the brass-colored screws (the hot side). You will see a small brass fin connecting the top and bottom screws. Use your lineman pliers to bend this tab back and forth until it snaps off completely. Do not touch the silver side (neutral) tab.
- Strip the Wires: Strip exactly 3/4 inch of insulation from the black, red, white, and bare copper wires. Do not nick the copper conductor, which creates a weak point that can snap under torque.
- Land the Ground (Bare Copper): Form a J-hook in the bare copper wire. Hook it clockwise around the green grounding screw at the bottom of the receptacle. Tighten firmly. (If using a metal box, you must also run a 6-inch ground pigtail from the receptacle to a grounding clip or screw on the metal box).
- Land the Neutral (White): Form a J-hook in the white wire. Hook it clockwise around either of the silver screws on the left side. Because the silver tab is intact, it does not matter which silver screw you use, though the bottom one is standard practice. Tighten until the wire is snug and the insulation sits flush against the washer.
- Land the Always-Hot (Black): Form a J-hook in the black wire. Hook it clockwise around the bottom brass screw. This will provide continuous, unswitched 120V power to the bottom half of the outlet.
- Land the Switched-Hot (Red): Form a J-hook in the red wire. Hook it clockwise around the top brass screw. This delivers the load-side power from the wall switch to the top half of the outlet.
- Fold and Secure: Carefully fold the wires into the back of the box. Push the ground and neutrals in first, followed by the hots. Mount the receptacle using the provided 6-32 machine screws, ensuring it sits flush and level. Install the faceplate.
Verify and Test Your Work
Do not plug in expensive electronics until you have verified the wiring with a meter.
- Turn the circuit breaker back ON at the panel.
- Set your digital multimeter to AC Voltage (VAC, 200V or 600V range depending on your meter's auto-ranging capability).
- Test the Bottom Half (Always Hot): Insert the black probe into the smaller (hot) slot of the bottom receptacle and the red probe into the larger (neutral) slot. Expected reading: 114V to 126V.
- Test the Top Half (Switch OFF): Ensure the wall switch is in the OFF position. Insert probes into the top receptacle's hot and neutral slots. Expected reading: 0.0V to 0.5V (ghost voltage is normal).
- Test the Top Half (Switch ON): Flip the wall switch ON. Measure the top receptacle again. Expected reading: 114V to 126V.
Finally, plug in a standard 3-prong receptacle tester (like a Klein Tools RT210) into both halves to verify correct grounding and polarity. The lights should indicate "Correct" on the bottom, and toggle between "Open Hot" and "Correct" on the top as you flip the switch.
The Most Common Botch (and How to Avoid It)
The single most frequent mistake when wiring for a switched outlet is failing to break the brass tab, or breaking the wrong tab.
- The Symptom of an Unbroken Brass Tab: If you land the black wire on the bottom brass screw and the red wire on the top brass screw but forget to snap the tab, the continuous hot (black) will backfeed into the switched hot (red). The result? Both halves of the outlet will be constantly live, and the wall switch will do absolutely nothing. Worse, if the switch is turned ON, it can create a dead short depending on the switch box wiring, instantly tripping the breaker with a loud pop.
- The Symptom of a Broken Silver Tab: If you accidentally snap the silver (neutral) tab instead of the brass tab, you have isolated the neutral paths. Because you only landed one white wire, the top half of the receptacle will have an "open neutral." The switch will appear to work, but plugging a lamp into the top half will result in the lamp not turning on, and a receptacle tester will flash an "Open Neutral" error.
The Fix: Always visually and physically inspect the receptacle before pushing it into the box. Run your fingernail over the brass side to confirm the gap is completely clear of metal debris, and verify the silver side still has its solid connecting fin.
Frequently Asked Questions
Can I wire a half-switched outlet using only 14/2 or 12/2 cable?
In new construction or new wiring runs, no. Modern NEC Article 404.2(C) requires a neutral conductor to be present at the switch box for future smart switch compatibility. A /2 cable only provides a hot and a neutral. To get a constant hot, a switched hot, and a neutral to the switch box, you must use /3 cable. If you are retrofitting an older home that already has an existing, code-grandfathered 2-wire switch loop, you can use the existing cable, but you must use the white wire as the always-hot (re-identifying it with black tape) and the black wire as the switched-hot, which can be highly confusing for the next person who works on it.
Which screw on the outlet is specifically for the red wire?
The red wire (switched hot) must land on the top brass screw. The black wire (always hot) lands on the bottom brass screw. While electrically the outlet doesn't "know" which brass screw is which once the tab is broken, standard trade practice dictates top-for-switched and bottom-for-constant to maintain consistency and make troubleshooting easier for future electricians.
Do I need to buy a special "split-wired" receptacle at the hardware store?
No. There is no special "half-hot" receptacle. You buy a standard 15A or 20A duplex receptacle (costing roughly $1.50 to $3.00). The receptacles are manufactured with scored break-off tabs on both the hot (brass) and neutral (silver) sides specifically so installers can configure them for split-wiring, multi-wire branch circuits (MWBC), or isolated grounds as needed.
Why does my breaker trip immediately when I turn on the switch for my newly wired outlet?
If the breaker trips the moment you flip the switch, you have created a dead short. The most likely cause is that you landed the always-hot black wire and the switched-hot red wire on the same side of the receptacle without breaking the brass tab, and your wall switch is wired in a way that ties the load back to the neutral or ground. Another possibility is that you accidentally landed the bare ground wire or the white neutral wire on one of the brass screws. Turn the breaker off immediately, open the box, and re-verify every wire color against the terminal screw color.
