Clothes dryers can be wired with cords that have three prongs as well as with four-prong cords, depending on the age of the wiring installation. Three-prong cords—and 3-slot outlets—were once the norm, but since 2008, Article 550.16(A)(2) of the National Electrical Code (NEC) has stipulated that connections for electric clothes dryers must be made with a 4-conductor cord and 3-pole, 4-wire,grounding-type plugs or by Type AC cable. This is the requirement for new construction or when a new clothes dryer circuit is installed, but older installations are allowed to retain their 3-prong, 3-slot dryer cord and outlet configurations.
It is, therefore, somewhat rare that you would want to change a 4-prong cord on an electric dryer to a 3-prong cord. It is much more common to go the other direction—to update by changing your dryer cord from 3-prongs to 4-prongs in order to meet the current code requirements. However, if you have moved into a new house or apartment that has a 3-slot dryer outlet, then you might want to change out your 4-prong cord with a 4-prong in order to make use of that existing outlet. It is entirely allowable to do this.
Tools and Materials
- 3-prong clothes-dryer electrical cord
- Magnetic nut driver set
Disconnect the 4-Prong Cord
- With the appliance unplugged, use a nut driver to remove the electrical connection cover plate to gain access to the electrical connections. After removing the retaining screw, simply slide the slotted side of the plate from the slot on the dryer.
- In order to protect the 4-prong electric dryer cord and hold it securely in place, a strain relief cord connector is used. This serves two purposes by keeping the cord from being cut on the metal of the machine while also protecting the electrical connections from being pulled loose if the cord is pulled on. To remove the clamp, squeeze the two halves together with pliers and remove the two screws. Remove the two halves of the clamps and the cord is ready to be removed.
- Now, disconnect the black wire—one of the two "hot" connections—from the left side post by removing the terminal screw. This is one-half of the 240-volt connection.
- Next, disconnect the red wire—another of the "hot" connections—from the right side post by removing the terminal screw. This is the other half of the 240-volt connection.
- Disconnect the white wire from the center connection. The white wire provides the neutral connection on a four-wire configuration.
- Disconnect the green wire grounding wire from the machine case by unscrewing the green screw.
- Remove the four-prong cord from the connection box.
Install the 3-Prong Cord
Before installing the three-prong cord, you will need to return your electrical connection to factory condition.
- Locate the white machine wire that is now connected to the neutral, or center, screw terminal. Disconnect it from there and reconnect it under the green grounding screw.
- Insert the loose end of the 3-prong cord through the installation hole found in the electrical connection access box.
- Unscrew the three connection screws using a magnetic nut driver, so the screws don't fall down inside of the machine.
- Connect the outer two wires—the hot wires—on the three-prong cord to the outer two screws, one on each screw.
- Now connect the center wire to the center post. You'll notice the white machine wire serves as the case ground connection, unlike the 4-prong cord connection, in which a separate green wire made the ground connection.
- To engage the strain relief fitting, slide one half of the clamp into the connection hole under the cord wire. This will be the half with the smaller holes. The clamp is bent at a 90- degree angle, so you'll have to twist it into place with the holes facing up.
- Now, install the larger-holed clamp half in the same manner.
- Squeeze the two halves together with pliers and insert the two screws into the holes. Tighten the two screws equally until snug.
- Reattach the electrical connection cover plate. Simply slide the slotted side of the plate into the slot provided on the dryer. Line the screw slot up with the mounting screw hole, and secure it with the retaining screw.