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Making Your Dryer Work With a 4-Prong Cord
Due to changes in the National Electrical Code (NEC), wiring for electric clothes dryers changed in 1996. Before the change, dryers used 3-prong cords that plugged into 3-slot electrical outlets (receptacles). This configuration did not include a dedicated ground connection; the dryer's equipment ground (case ground) was connected to the neutral conductor in the dryer cord and the household circuit.
Since the Code change, dryers must be wired with separate neutral and ground wires, which... requires the use of 4-prong electrical cords plugged into 4-slot outlets. Also, all newly installed dryer receptacles must be 4-slot. Homeowners moving into a newer home often find that the 4-slot dryer outlet does not fit their older dryer with a 3-prong cord.
Note: It's still legal to use a dryer with a 3-prong cord and an older-style receptacle. For example, if you buy a new dryer set up for a 4-prong cord, you can replace the cord with a 3-prong version to fit a 3-slot receptacle in your home. To do this means following a procedure similar to this project, but in reverse—removing the 4-prong cord and installing a 3-prong cord.
What Is the Difference in Wiring?
The key difference in the wiring configuration between 3-prong and 4-prong is that with the older setup, the 3-prong cord has only two hot wires and one neutral wire; there is no separate ground wire. Therefore, the dryer's neutral was tied to the ground connection on the case of the dryer.
A 4-prong cord, by contrast, has a separate ground wire, and the dryer's neutral and ground are not connected together. When you convert from the 3-prong to the 4-prong configuration, you must make sure that the dryer's neutral terminal is not connected to the case ground.
Warning: Never plug in a dryer cord unless it's fully connected to the dryer. Plugging in a cord sends 240 volts of electricity to the bare wire ends of the cord. If the ends touch together or touch you, they'll create a potentially lethal short circuit.
Tools and Materials You Will Need
Continue to 2 of 8 below.
- Phillips screwdriver
- Nut driver or socket wrench (as needed)
- UL-listed, 30-amp, 4-prong dryer cord
- Strain-relief fitting for 4-prong cord
- Adjustable pliers (optional)
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Step 1: Uncover Electrical Connections on the Dryer
Continue to 3 of 8 below.
- Make sure the dryer is unplugged from the electrical source.
- Remove the metal plate covering the cord's wiring connections on the back of the dryer. It should be directly above the place where the cord comes out.
- Use a magnetic screwdriver or nut driver (or socket wrench) to remove the plate's screws, and set the plate aside. With magnetic tools, you're less likely to drop screws inside the dryer.
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Step 2: Remove the Strain-Relief Fitting
Remove the screws on the strain-relief fitting securing the cord to the back panel of the dryer. Separate the two halves of the fitting and pull them out of the hole one at a time.Continue to 4 of 8 below.
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Step 3: Disconnect the Old Cord
Disconnect the old 3-prong cord by removing the three screws securing the wire ends to the dryer's terminal block. The two outer terminals are the hot terminals, and the center terminal is the neutral. There may be a short white wire or metal strap joining the neutral terminal and the ground screw, or there may be a white wire coming from inside the dryer and connecting to the ground screw. This is the 3-wire configuration that ties the case ground to the neutral cord wire. Pull the cord out... through the hole to remove it from the dryer.Continue to 5 of 8 below.
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Step 4: Separate the Dryer's Neutral from the Ground
Disconnect the dryer neutral from the ground screw to convert the wiring configuration from 3-prong to 4-prong. You may have one of two different configurations:
Continue to 6 of 8 below.
- If there is a white wire coming from inside the dryer and connecting to the ground screw, remove it from the ground screw and connect it to the neutral (center) terminal on the dryer's wiring block.
- If there is a short white wire or metal strap connected to the neutral terminal on the wiring block and the ground screw, remove the wire... or strap from the ground screw.
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Step 5: Connect the New 4-Prong Cord
Install the new 4-prong cord by inserting the loose-wire end through the hole in the dryer's back panel and making the following connections:
Continue to 7 of 8 below.
- Connect the green cord wire to the ground screw.
- Connect the white cord wire to the center neutral terminal. If your dryer has a pre-attached white wire, both wires will be connected the neutral terminal.
- Connect the black cord wire to either the left or right terminal, next to the center neutral. The hot terminals are interchangeable; each can connect to... the black or the red wire, but only one wire goes on each terminal.
- Connect the red cord wire to the other hot terminal.
- Tighten each terminal screw firmly, and double-check them to make sure they are tight.
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Step 6: Attach the Strain-Relief Fitting to the New Cord
Install a new strain relief fitting to secure the 4-prong cord.
- Slip the tab of the top half of the fitting into the hole and position the saddle (semi-circle) of the fitting over the top of the cord.
- Do the same with the bottom half of the fitting below the cord.
- Squeeze the two halves together (sometimes it helps to use pliers to gently squeeze them together), and secure the halves with the fitting screws.
- Snug the screws so the cord is held firmly but is not deformed by the pressure.
Note: Your... old strain-relief fitting probably won't work for your new 4-prong cord. 3-prong cords typically are flat, while 4-prong usually are round and require a fitting with a rounded area in its center. Do not use a strain relief that doesn't fit the cord.Continue to 8 of 8 below.
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Step 7: Reinstall the Dryer's Electrical Coverplate
Reinstall the cover plate with its screws. To test the dryer for proper operation, check the dryer's control knob(s) to confirm that everything is in the OFF position, then plug in the dryer into a 4-prong dryer outlet. Run the dryer for a few minutes to make sure everything works. Connect the dryer vent duct before using the dryer.