To wire a standard 15-amp combo switch where the toggle controls a separate light fixture and the built-in receptacle remains always hot, connect the bare copper ground wire to the green screw, the white neutral wire to the silver screw, the black line (hot) wire to the brass screw, and the black or red switched load wire to the black screw. This configuration assumes you are working on a standard US 120V, 15-amp circuit using copper NM-B cable, and that a dedicated neutral wire is present in your switch box.

Decision Tree: Pick Your Combo Switch Configuration

Combo switches (a single-gang device combining a toggle switch and a duplex receptacle) are not one-size-fits-all. Before stripping any wire, determine your exact goal using this decision path to select the correct internal wiring method and device.

If your goal is... And your box has... Then choose this configuration... Concrete Device Pick
Switch controls a ceiling light; outlet is always powered for a vacuum or phone charger. Line hot, Neutral, Ground, and a separate Load wire going to the light. Switched Load / Always Hot Receptacle (Default for 90% of DIYers) Leviton 5243-W (15A) or Eaton 5241 (15A)
Switch turns the built-in outlet on and off (e.g., for a lamp or garbage disposal). Line hot, Neutral, Ground (No separate light load). Switched Receptacle (Requires breaking the brass fin tab on specific models) Leviton 5243-W (15A) with tab removed
You are on a 20-amp breaker and this is the ONLY receptacle on the entire circuit. 12 AWG wire, 20A breaker. 20A Switched Load / Always Hot (NEC 210.21(B)(3) mandates 20A rating for single-receptacle circuits) Leviton 5245-W (20A)
The 20-Amp Trap: Many DIYers put a 15-amp combo switch on a 20-amp kitchen or bathroom circuit. Under NEC Article 210.21(B)(3), a 15A receptacle is only allowed on a 20A circuit if there are multiple receptacles on that same circuit. If this combo device is the only outlet on the 20A run, you must use a 20A rated device and 12 AWG wire.

Tools, Materials, and Device Ratings

Do not start this job without verifying your box fill and having the correct termination tools. Combo devices are deeper than standard switches and require adequate cubic inch volume.

  • Device: Leviton 5243-W (15A, 120V, single-pole combo switch/receptacle).
  • Wire: 14-2 NM-B (Romex) for line power; 14-3 NM-B if you are routing a switched leg and neutral up to a light fixture from this box.
  • Wire Strippers: Klein Tools 11063W (strips 14-12 AWG cleanly without nicking copper).
  • Voltage Tester: Klein NCVT-2 (Non-Contact Voltage Tester) for initial sweep.
  • Digital Multimeter (DMM): Fluke 117 or Klein MM400 for definitive dead-circuit verification and post-wiring testing.
  • Screwdriver: #2 Phillips and 1/8-inch flathead (magnetic tip preferred).
Box Fill Calculation (NEC 314.16): A combo switch counts as two current-carrying conductor equivalents for box fill calculations. If you are using 14 AWG wire (2.0 cubic inches per conductor), the device itself takes up 4.0 cubic inches. Add your incoming wires, outgoing wires, and grounds. If your single-gang box is a standard 14-cubic-inch blue plastic nail-on box, you are likely at or over maximum capacity. Upgrade to an 18-cubic-inch deep single-gang box or a 4x4 square box with a single-gang mud ring if the wires are being crushed.

Mains Safety Protocol: De-Energize and Verify

Working on line-voltage (120V AC) devices requires strict adherence to lockout/tagout principles. Never trust a wall switch or a single tester to confirm a circuit is dead.

  1. Shut off the breaker: Locate the correct 15A or 20A breaker in your main panel and switch it to the OFF position. If possible, apply a physical lockout tag or tape the breaker so no one else turns it on while you are working.
  2. Initial NCVT Sweep: Remove the wall plate. Hold your Non-Contact Voltage Tester near the existing switch terminals. It should not beep or flash red. (Note: NCVTs can give false negatives on shielded wires; this is only step one).
  3. Definitive DMM Verification: Set your Digital Multimeter to AC Volts (V~). Place the black probe on the bare copper ground wire and the red probe on the black hot wire. The reading must be 0.0V. Next, test between the black hot and white neutral. It must also read 0.0V.
  4. Test the meter: Verify your DMM is working by testing a known live outlet in an adjacent room before and after your switch box test.

Step-by-Step Wiring: Switch Controls Separate Light, Outlet Always Hot

This procedure assumes you have a 14-2 NM-B cable bringing power into the box (Line), and a 14-3 NM-B cable leaving the box to feed a light fixture (Load + Neutral). Always use the side-screw terminals or the screw-clamp back-wiring holes. Never use the push-in stab connectors on combo devices, as the internal leaf springs overheat and fail under continuous receptacle loads.

  1. Prep the wires: Strip exactly 3/4-inch of insulation from the 14 AWG black, white, and red wires using your wire strippers. If reusing old wires, snip off the oxidized ends and re-strip. Fold the bare copper grounds together and pigtail them with a wire nut, leaving one 6-inch bare tail for the device.
  2. Terminate the Ground (Green Screw): Form a J-hook in the bare copper ground tail. Loop it clockwise around the green grounding screw on the combo device. Tighten firmly. The clockwise loop ensures the screw pulls the wire tighter as you drive it, rather than pushing it out.
  3. Terminate the Neutral (Silver Screw): Connect the white neutral wire from your power source (and pigtail to the white neutral going to the light, if applicable) to the silver screw. The receptacle requires this neutral to complete the 120V circuit for anything you plug in. Tighten to 14 in-lbs if using a torque screwdriver.
  4. Terminate the Line Hot (Brass Screw): Connect the black wire bringing constant power from the panel to the brass screw. This feeds both the switch mechanism and the always-hot receptacle internally.
  5. Terminate the Switched Load (Black Screw / Black Lead): Connect the red wire (or black wire, if using 14-2 for a switch loop) traveling up to the light fixture to the black screw. On some newer Leviton 5243 models, this may be a black pigtail wire lead instead of a screw; connect it to your load wire using a wire nut.
  6. Dress the box: Carefully fold the wires in a Z-pattern (grounds in the back, neutrals folded next, hots on top). Push the device into the box, ensuring no bare copper is touching the brass or black screws. Secure with the provided 6-32 mounting screws.

Verify and Test: Meter Readings and Common Botches

Before installing the wall plate and plugging in a device, restore power at the breaker and run this verification sequence.

Expected Meter Readings

Test Points (DMM Probes) Switch State Expected Reading Meaning
Receptacle Hot Slot to Neutral Slot N/A 114V - 126V AC Receptacle has constant, always-hot power.
Receptacle Hot Slot to Ground Slot N/A 114V - 126V AC Grounding path is intact and bonded.
Load Wire (at ceiling) to Neutral OFF 0.0V AC Switch is successfully breaking the circuit.
Load Wire (at ceiling) to Neutral ON 114V - 126V AC Switch is passing line voltage to the light.

The Most Common Botch: The "Bootleg Neutral"

The Scenario: You are replacing an old single-pole switch in a house built before 1985. The box only has a 14-2 cable (Black, White, Bare). The white wire was actually being used as a "switch loop" hot, not a neutral. You wire the combo switch, plug in your phone charger, and get 0V at the outlet.

The Dangerous Fix: A frustrated DIYer might tie the silver neutral screw to the bare copper ground wire to "complete" the circuit. Never do this. This is called a bootleg neutral. It will energize the grounding system of your home, creating a severe shock hazard if a ground fault occurs elsewhere, and it will immediately trip any upstream GFCI or AFCI breaker.

The Symptom: Outlet reads 0V, or breaker trips instantly when a load is plugged in. A plug-in receptacle tester will show "Open Neutral" or "Hot/Ground Reverse."
The Real Fix: A combo switch requires a true neutral wire in the box. If your switch box only has a switch loop (no neutral), you cannot install a combo receptacle without pulling a new 14-3 or 12-3 NM-B cable from the light fixture or panel to bring a dedicated neutral down to the switch box. If pulling wire is impossible, abandon the combo switch idea and use a standard single-pole toggle switch.