How to Change a 4-Prong Dryer Cord and Plug to a 3-Prong
My New Home Needs a Dryer Plug Adapter
Congratulations! You've just moved into your new home, the new drapes are up, and the washer and dryer are ready to be put into place. But wait! The dryer cord won't plug in—the dryer cord has four prongs, but the wall receptacle only has three holes! What's up with this?
What's up is that in 1999 the National Electric Code instituted a change, requiring all new dryers and home dryer receptacles to have 4 prongs instead of the older 3-prong style. That fourth prong is a ground wire and is there for better electrical safety.
Now, it would be convenient if there was a dryer plug adapter that you could plug into that three-pronged receptacle so that you could plug your dryer into that—but there isn't. You will have to change the dryer cord to make it fit.
The good news is that dryer cords are readily available and fairly inexpensive, and it isn’t very hard to switch them. A screwdriver and a pair of pliers will do the job, although some nut drivers would be nice.
Now if the situation with your dryer cord and outlet is backwards from this—that is, you have a three-pronged cord and a four-pronged outlet—you are looking at the wrong article. Look at this article instead: Changing A 3 Prong To 4 Prong Dryer Cord And Plug.
If Your Wall Plug Looks Like This...
But the Cord on Your Dryer Looks Like This...
You Need to Buy a Cord That Looks Like This...
Removing the Old Four-Prong Plug
Begin by unplugging the dryer. There is high voltage inside (240 volts) that can give you a very nasty shock, even kill you. Make sure there is no chance of this, by unplugging the dryer before proceeding any further.
There will be some kind of connector holding the dryer cable to the wall of the dryer so that it doesn't pull out. The most common type is a clamp with two screws on the outside that can be tightened to squeeze the wire into place. Loosen these screws so that the wire can slide out of the dryer.
Remove the cover plate from the wire terminal block, exposing the wires inside. Note where each color of wire terminates. Normally, you will see a row of three terminal screws, with the red and black wires connected to the two outside screws, the white wire connected to the center screw, and the green wire connected to the frame of the dryer.
Remove each wire from the screw or stud holding it, making sure to save all nuts or screws.
Work the old wire out of the connector that holds it to the wall of the dryer, and set it aside for possible future use. You never know when you might move again, and Murphy's Law says that if you do, it will be back into a home with a four-prong dryer plug!
Installing the Three-Prong Dryer Cord and Plug
Once the four-wire cord is removed, it is time to install the new three-wire cord and plug. Work the wire through the connector, but do not tighten it yet. The red and black wires go to the outer two terminals (in the photo the dryer wires are black and blue) and the white wire goes to the terminal in the center of the terminal block. While the red and black wires are interchangeable, the white wire is not; make sure it goes to the center terminal, where the old white wire was.
Most three-wire cords do not have colored wires, so instead of matching colors, identify the wires using the relative position of the wires in the cord. The center wire of the three will always go to the center (white) terminal; the outer two wires go to the outer terminals. The outer two wires can be interchanged, but never put the center wire of a flat, three-wire cord on anything but the center terminal.
Your three-prong cord will not have a green ground wire. In place of that wire a ground strap or short piece of #10 wire (preferably green) must be installed. One end should go to where the green wire on the old cord went, and the other end to the terminal where the white wire went. Do not ignore this step! You must have a "jumper" of some kind, a wire or strap, installed between the dryer frame and the white wire. This jumper is the only thing that grounds the dryer. Without it, if there is an electrical problem later, the frame may become energized and present a huge shock hazard.
The photo shows a metal strap installed; it goes from the white wire down the side of the terminal block, and is screwed to the dryer frame. If this strap is not available (and it usually isn't) purchase a one-foot piece of #10 green wire, strip an inch of insulation from each end, and install that wire between the connector the white wire used to go to and the connector on the frame where the green wire used to go.
With the wires all terminated, tighten the connector on the outside of the dryer that holds the cable securely.
It is wise to turn the power off at this point, just in case something has been wired wrong. With the power off, plug the dryer into the wall outlet and turn the breaker back on. Test the dryer for proper operation and you're done. Congratulations on doing your own home repair job! It wasn't so bad, was it, even though that dryer cord adapter you really wanted isn't available?
A final thought: now that you have your dryer operating properly, the vent hose may need some attention. Older, plastic, vent hoses are not recommended as a fire hazard, and even newer metallic ones deteriorate over time. Many dryers are placed very close to the wall where the exhaust vent is located, requiring that the hose be badly kinked in order to hook up to it, and rigid metal elbows are available to help alleviate this problem. Neither the dryer vent or vent elbows are expensive; consider replacing them and at a minimum clean out the vent hose and the vent opening outside your home. Whether you purchase your new cord at a local home improvement store or through the Amazon link above, both vent hoses and elbows are available and can be purchased at the same time as the new cord.
Questions & Answers
You say there is no adapter, 4 to 3 prong, but I have found several! What's the deal?
Be very careful: I find lots of adapters made for welders or other 240V stuff, so they can run off the dryer outlet. But nothing for a dryer. Although the plugs may LOOK similar, they won't fit unless specifically made for a dryer. They must carry the NEMA designation of 10-30P (3 wire plug) and 14-30R (4 wire receptacle). Or, if that's backwards, 10-30R and 14-30P (4 wire plug, 3 wire receptacle).
I also see lots of "twist-lock" cords that will plug into a dryer outlet: these are 240V extension cords that are plugged together and twisted to lock them in place. A dryer cord does not do that and won't fit even though it looks similar.
Amazon used to carry one, and it still shows up, but has been unavailable for some time now. Problem is that the adapter, when 4 prong (dryer) to 3 (wall outlet), must use the ground as a neutral, and that isn't legal to do which in turn means there can be no UL label. That raises the possibility of liability, which few companies are willing to do. If you go the other way, 4 prong outlet and 3 prong dryer, you now have to connect the neutral to the ground inside the adapter and again, that isn't legal outside of a dryer that is grandfathered under the law. Same thing: no UL label and increased liability.
There is a green wire that is coming from the dryer and connects to the frame. Should it be moved from the frame to the center wire?
No. Instead of a jumper wire, or a ground strap, must be added, going from the center terminal to where that green wire connects to the frame. Leave the green wire where it is and add the jumper.
I am changing a four prong to a three prong, but the green and white wires from the cord were both attached to the center connection on the dryer. There is a green screw on the dryer with a white wire going into the dryer, where to, I can't see. Was this dryer previously converted to a four prong? Not sure what to do about the ground. I was told by the previous owner the dryer is 4 or 5 years old.
It sounds like it was previously converted. Age isn't much of an indicator; at 5 years old it should have come with a 4 prong but could have been converted to a 3, then back to a 4.
In any case, the new center wire on the 3 wire cord will go to the center terminal, with a jumper from there to the frame of the dryer - the green screw on the frame would be the best place to put the other end of the jumper. Leave the existing white wire where it is; it will be used to operate the controls and needs to be there.
© 2011 Dan Harmon