How to Wire a 4-Prong Receptacle for a Dryer

Receptacle with a 4-prong secured to the wall

The Spruce / Kevin Norris

Overview
  • Working Time: 1 hr
  • Total Time: 1 hr
  • Skill Level: Advanced
  • Estimated Cost: $50

Before 1996, electric dryers were supplied by a dedicated circuit that had three conductors: two hot wires and a third that contained both a ground wire and a neutral wire. There was no dedicated ground slot on the receptacle (outlet), and dryer cords had no ground wire or ground prong. This system worked pretty well (and is still in use in many homes today), but there's more potential for an electrical shock since the ground and neutral wires are combined.

In 1996, the ​National Electrical Code (NEC) began requiring 4-conductor outlets with a separate ground that eliminates the possibility of a current traveling back to the machine, causing shock or even fire. To be code-compliant, all newly installed outlets for dryers must be compatible with 4-prong, grounded dryer cords. ​​

Wiring for a 4-Prong Dryer Receptacle

A 4-prong dryer outlet is wired as a 120/240-volt circuit. The 120-volt service is for the dryer's timers, sensors, and other electronics, while the 240-volt service supplies power to the heating elements. The NEC requires that dryers have a dedicated circuit with a minimum of 30 amps. This calls for a 30-amp, double-pole breaker wired with 10 AWG wire.

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What You'll Need

Equipment / Tools

  • Wire strippers
  • Needle-nose pliers
  • Screwdriver
  • Flashlight
  • Voltage tester

Materials

  • 4-slot dryer outlet
  • 4x4-inch electrical box
  • 30-amp double-pole breaker (must be compatible with your service panel)
  • 10-3 NM-B cable (with ground) or EMT conduit and 10-gauge greenfield wire

Instructions

Materials and tools to wire a 4-prong receptacle for a dryer

The Spruce / Kevin Norris

  1. Install a Receptacle Box and Run the Cable

    In a standard installation with nonmetallic (NM) cable, 10-3 NM-B (with ground) cable is run from the main service panel to a recessed outlet box. If the outlet is surface-mounted (like on a concrete or block wall), the circuit is usually run with insulated (THHN/THWN) wires inside nonmetallic or EMT conduit. The outlet may be a special surface-mount receptacle or a standard dryer receptacle installed in a surface-mounted box.

    How you connect the cable or wires into the box will depend on the installation. With NM cable in finished walls, the cable is threaded into the box and secured with a cable clamp. In surface-mounted conduit installations, the conduit is secured to the box with a collar and individual conducting wires are snaked through the conduit and into the box.

    NM cable and THHN/THWN wires pulled from inside a surface mounted outlet box

    The Spruce / Kevin Norris

  2. Make the Ground Wire Connection at the Outlet

    Connect the bare copper (or green insulated) ground wire to the ground screw on the outlet.

    If the outlet is mounted in a metal electrical box, join the circuit ground wire to two grounding pigtails; connect one pigtail to the outlet's ground screw and the other to the ground screw on the box. 

    Bare copper ground wire connected to the outlet ground screw with screwdriver

    The Spruce / Kevin Norris

  3. Connect the White Neutral Wire at the Outlet

    Strip away about 3/4-inch of insulation from the white wire in the cable. Connect the white neutral wire to the silver-colored (neutral) terminal on the outlet. Usually, the connection involves inserting the bare wire into the neutral slot, then securing it by tightening a screw. In some styles, you may need to loop the wire around a screw terminal before screwing it down.

    White neutral wire connected to the silver-colored terminal on the outlet with screwdriver

    The Spruce / Kevin Norris

  4. Connect the Two Hot Wires

    Next, strip about 3/4-inch of insulation from the red and black hot wires. Secure them to the two hot terminals on the outlet.

    Red and black wires stripped and secured to hot terminals on outlet

    The Spruce / Kevin Norris

  5. Secure the Outlet

    Insert the outlet into the box, carefully tucking the wires in place, then secure it using the mounting screws. Install the outlet cover plate.

    Outlet inserted into recessed outlet box and secured with mounting screws

    The Spruce / Kevin Norris

  6. Prepare to Install the Circuit Breaker

    Turn off the main circuit breaker in the service panel. Remove the panel cover to expose the panel wiring. Locate two adjacent empty slots in the service panel where the double-pole breaker will fit. Remove the slot tabs on the panel cover where this breaker will be located.

    Open a punch-out in the side wall of the service panel, then insert the cable through the opening and secure it with a cable clamp. As you are threading the cable into the panel, be careful not to allow the wires to brush against the bus bars.

    You will need plenty of excess wire; strip away at least 18 inches of the outer jacket from the cable. Strip about 3/4-inch of insulation from the ends of the white, black, and red wires.

    Warning

    If you are not experienced with working inside an electrical service panel, this is the point where you should hire an electrician to install the circuit breaker. Even if you've installed the circuit cable, box, and outlet yourself, you can still have an electrician make the final connections at the service panel. 


    Service panels pose a deadly risk of shock because the utility service cables feeding the panel—and the terminal lugs they connect to inside the panel—remain live at all times. Shutting off the main circuit breaker does not turn off the power to the service feed.

    Service panel wiring inserted through side of panel and secured with cable clamp

    The Spruce / Kevin Norris

  7. Test the Branch Circuits

    Test the branch circuits inside the panel with a voltage tester to confirm the power is off. This is done by touching one probe of the tester to a screw terminal on the breaker while touching the other probe to the ground bus bar. Remember that the incoming power from the utility service lines will remain live; do not touch either of the hot bus bars running down the back of the panel.

  8. Connect the Ground Wire

    Connect the ground wire from the dryer outlet's circuit cable to the panel's ground bus bar. This involves inserting the bare end of the wire into a slot in the ground bus bar and tightening the set screw to secure the wire. Carefully fold the excess wire and arrange it along the outer edge of the panel.

    Ground wire connected to service panel's ground bus bar

    The Spruce / Kevin Norris

  9. Connect the Neutral Wire

    Connect the white neutral circuit wire by inserting the bare copper end of the wire into a slot in the panel's neutral bus bar, then tightening the set screw. Carefully fold the excess wire and tuck it along the edge of the service panel.

    White neutral circuit wire by inserted into the panel's neutral bus bar

    The Spruce / Kevin Norris

  10. Connect the Hot Wires to the Circuit Breaker

    Connect the red and black hot circuit wires to the two screw terminals on the 30-amp, double-pole circuit breaker. For most breakers, this involves simply inserting the bare ends of the wires into the slots on the breaker and tightening the set screws. Carefully fold the excess wire and tuck it along the edge of the service panel.

    Red and black hot circuit wires inserted into breaker slots and tightened with screwdriver

    The Spruce / Kevin Norris

  11. Mount the Circuit Breaker

    Line up your new breaker so the clips slide over the mounting hooks adjacent to the hot bus bar. Press the breaker down firmly until it snaps into place. Depending on the brand of your service panel, inserting the breaker can be either a pivoting action or a firm inward push to snap the breaker onto the bus bars.

    Breaker pressed into mounting hooks adjacent to hot bus bar

    The Spruce / Kevin Norris

  12. Finish the Installation

    Reinstall the panel cover. Turn off all the branch circuit breakers in the panel. Turn on the main breaker, then switch on each of the branch circuits, one at a time. This process prevents the sudden power surge that occurs if the main breaker is turned on while all the circuit breakers are activated.

    Service panel cover replaced and secured with screwdriver

    The Spruce / Kevin Norris

  13. Test the Outlet

    Use a voltage tester to verify that the dryer outlet is carrying power.

    Yellow voltage tester checking power in receptacle outlet

    The Spruce / Kevin Norris

  14. Install the Appliance Cord

    You are now ready to install the 4-prong appliance cord on your dryer and plug it into your revamped dryer outlet.

    4-prong appliance cord from dryer installed into outlet

    The Spruce / Kevin Norris

When to Call a Professional

This project requires a good knowledge of—and experience working with—electrical circuits. It involves making circuit connections at the main service panel and should not be attempted unless you are fully confident in your abilities. If you are not certain, it is best to have this work done by a professional electrician.

Tips for Installing a Dryer Outlet

  • Find a good location: Position the dryer outlet box in a convenient location for both the dryer cord and the dryer vent. Whenever possible, dryers should be near an exterior wall to minimize the length of the vent run. 
  • Position the outlet at a convenient height: Local codes typically do not specify an installation height for dryer outlets, but it's helpful to be able to reach the plug without moving the dryer all the way out from the wall. A height of about 30 to 36 inches from the floor usually suffices to keeps the plug accessible while hiding it from view behind the dryer.
  • Orient the outlet properly: Orient the outlet so the L-shaped (neutral) slot is at the bottom. This ensures the dryer cord will extend downward from the outlet.