How to Convert a 4-Prong Dryer Cord to Fit a 3-Slot Outlet
When moving a newer electric dryer into an older house, it's common to find that the dryer cord and plug don't fit the 240-volt dryer outlet. The dryer's plug has four prongs, yet the outlet only has three slots.
If you're a homeowner, you can switch out the four-prong cord for a three-prong cord—no electrician necessary. Some new dryers, in fact, don't include power cords at all, allowing consumers to buy the type of cord that matches their home's dryer outlet. What makes this an attractive solution for DIYers is that the dryer outlet never needs to be opened or worked on—only the dryer cord.
Before You Begin
Before the mid-1990s, most electric clothes dryers operated with three-prong plugs that fit into three-slot outlets. Since 1996, the electric code has required four-slot outlets that accept only four-wire cords.
There are several workarounds for mismatched cords and outlets. Replacing the dryer cord is by far the easiest solution and the one that most DIYers pursue when they are faced with the problem.
While the four-prong and four-slot arrangement is considered to be an improvement, the electrical code allows you to replace the four-prong cord with a three-prong cord to match the outlet.
Safety Considerations
Even though you will be working on an unplugged dryer, it is best to be cautious and shut off the circuit powering the dryer before you unplug it or plug it back in.
Make sure that you attach a strain-relief clamp to the new cord. Because of dryers' high voltages and their tendency to move, it's important to secure the cord.
Need more help? Talk to an electrician near you
What You'll Need
Equipment / Tools
- Voltage tester
- Pliers
- Magnetic nut driver
- Screwdrivers
Materials
- UL-listed three-prong dryer cord with strain-relief clamp
Instructions
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Shut Off the Breaker
Unplug the dryer. In the main service panel (breaker box), find the double-pole circuit breaker that controls the clothes dryer and flip the breaker to the OFF position.
Most dryer circuits have 30-amp breakers, indicated by a "30" stamped on the switch bar of the breaker. A double-pole breaker is twice as wide as a standard (single-pole) breaker, and most service panels have only a few double-pole breakers.
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Check For Power
At the dryer outlet, check for power using a non-contact voltage tester. Rotate the dryer to a position where you have access to the back panel. Disconnect the dryer vent to move and work on the dryer.
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Remove the Dryer's Electrical Connection Cover
Use a screwdriver to remove the cover on the electrical connection box on the back of the dryer. The box is located just above where the power cord comes out of the dryer and is attached with one or two screws. Set the cover and screws aside.
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Detach the Four-Prong Cord
Remove the strain-relief clamp holding the cord by removing the two screws that join the two halves of the clamp together. Separate the halves of the fitting and pull them out of the hole individually.
Using a magnetic nut driver or screwdriver, disconnect the black and red cord wires from the left-side and right-side terminals on the dryer's terminal block. These are the hot wire connections. Disconnect the white wire from the center terminal. Disconnect the green grounding wire from the machine case by unscrewing the green grounding screw.
Slide the four-prong cord out of the connection box.
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Jump the Neutral to the Ground
For a three-prong cord to work correctly, you must connect the dryer's neutral terminal to the case ground with a jumper.
Locate the white machine wire that is connected to the neutral (center) screw terminal. Disconnect it and reconnect it under the green grounding screw. Tighten the screw firmly.
Alternatively, the dryer may have a metal bonding strap (typically connected under the ground screw) instead of a white machine wire. If so, attach the strap to both the ground screw and the neutral (center) terminal.
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Connect the Three-Prong Cord
Thread the loose end of the three-prong cord through the hole in the electrical connection box. Connect the outer two wires (the hot wires) on the cord to the outer two screw terminals on the dryer, one on each screw. Connect the center wire to the center (neutral) terminal.
If there is a bonding strap for the ground, it must be connected to the neutral terminal along with the center cord wire.
Tighten all wire connections firmly.
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Install the New Strain-Relief Clamp
Slide one-half of the strain-relief clamp into the hole under the cord wire. Fit the other half of the clamp in the same way but on the top of the cord. Squeeze the two halves together with pliers and thread the screws into the holes. Tighten the screws until the cord is secure.
Warning
Do not reuse the original strain-relief clamp with the new three-prong cord. Clamps for four-prong cords are round and will not properly fit the flat shape of a three-prong cord. Use the strain-relief clamp that comes with the new cord, or buy a compatible clamp separately.
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Plug in the Dryer
Reattach the connection box cover plate with its screw(s). Slide the dryer into place, and reconnect the dryer vent duct, if necessary. Plug the cord into the outlet. At the main service panel, turn the dryer's circuit breaker back to the ON position, then test the dryer for proper operation.
When to Call a Professional
Though converting a 4-prong plug into a 3-prong plug should be within the skill set of most intermediate-level DIYers, call an electrician to do the job if you're not comfortable doing the work.