Electric clothes dryers are usually sold without power cords attached, and as annoying as that may be, there's a good reason for this omission. In 1996, the National Electrical Code (NEC) changed the requirements for electric dryer wiring and cord connections. The old cords had three-prong plugs that fit three-slot wall outlets. In three-prong cords, there were two hot wires, with the third wire serving as both the neutral and the ground connection. To make this work, the dryer was configured so that the chassis' ground connection was "jumpered" to the neutral connection by means of a small metal strap in the connection box.
All this changed with the 1996 code revision, where new installations required that dryer outlets must be wired to accept four-prong cords, with separate neutral and ground wires. This also required a slightly different configuration in the dryer's connection box, in which the neutral and ground terminals were no longer jumpered together. This configuration slightly improves the protection against shock, since the machine's chassis now has its own grounding pathway.
The NEC (and most local building codes) still permit the use of three-prong dryer cords in houses that have the old style of dryer outlet. And since your dryer might be older or newer than your outlet, dryer manufacturers don't bother giving you an appliance cord because it might not work for your situation. That's why the cords are sold separately.
This project shows you how to install a new four-prong dryer cord for use with a four-slot outlet, which has been the standard for more than 20 years. Alternatively, if your house has an old three-slot dryer outlet, you can install a three-prong dryer cord on your new dryer to make it compatible with a three-slot dryer outlet.
Equipment / Tools
- Screwdriver or nut driver
- UL-listed, four-prong dryer cord (must match amp rating for dryer and outlet; most are 30-amp)
- Strain-relief fitting (must be an appropriate size and shape for the cord)
Expose the Wire Connection Block
Locate the electrical cover plate on the back of the dryer. It will be near a hole about 3/4-inch in diameter in the dryer's back panel. Using a screwdriver or nut driver, remove the screws on the cover plate. Remove the plate from the dryer to expose the wiring terminal block for the cord connections. Set the plate and screws aside.
Install the Cord
Insert the dryer cord into the hole near the terminal block. Secure the green cord wire under the ground screw on the dryer body. Tighten the ground screw firmly with the screwdriver or nut driver.
Connect the Cord Wires
Connect the remaining three cord wires to the terminals on the terminal block. Start by connecting the white cord wire to the center (neutral) terminal on the block. Then, connect the black cord wire to the terminal at the left or right of the center terminal; the left and right terminals are the hot terminals and are interchangeable.
Finally, connect the red cord wire to the remaining hot terminal.
Tighten all terminal connections firmly, using the screwdriver or nut driver.
Secure the Cord
Install a new strain-relief fitting to secure the cord where it enters the dryer panel. These fittings typically have a top and bottom half. Remove the screws from the fitting and separate the two halves. Insert the tab of each half into the dryer cord hole, so it is flat against the inside of the dryer panel. Fit the two halves over the cord and reinstall the fitting's screws. Tighten the screws so the cord is held firmly, but make sure the fitting does not deform the cord or pinch the insulation.
Reattach the Cover Plate
Set the cover plate into place over the terminal block, and secure it with its mounting screws. Make sure all dryer controls are off and plug in the dryer to the four-slot outlet. Turn on the dryer and test it for proper function.
Variation for Three-Prong Cords
If you happen to have an older three-slot dryer outlet, the electrical code does allow you to install a three-prong cord to fit that outlet. The installation process is much the same as for four-prong cords with one exception:
In the dryer's wire connection box, there must be a metal jumper between the center neutral terminal and the ground terminal. If you are installing a three-prong cord, the center wire (the ground/neutral wire) is connected to this center ground/neutral connection, and the other two wires are connected to outer terminals (both hot) on the dryer.
NC Amendment 250.140 Frames of Ranges and Clothes Dryers. Electrical Continuing Education & Electrical License Renewal Services.