Changing a 3-Prong to 4-Prong Dryer Plug and Cord
My Dryer Cord Has 3 Prongs but the Plug Requires 4!
So you've moved into your new home and gotten the dryer wrestled into place. The vent is hooked up, ready to go, but the cord doesn't fit the socket! Your dryer has only 3 prongs, but it needs 4 prongs to fit. What's up with this?
(If your dryer has 4 prongs and needs 3, try the one about changing a 4 prong dryer cord into a 3 prong cord).
In 1999, the National Electric Code began requiring all dryer receptacles to be the 4 prong type for increased safety, but homes built prior to that time used the older 3 prong variety. If you are moving from an older home into a newer one, you will likely find that the dryer plug won't fit.
The Best, Safest, and Cheapest Solution Is to Install a New Cord
This is not hard; most homeowners with even a few basic tools can do it. You'll need...
- a screwdriver,
- a nut driver set,
- and possibly a pair of wire strippers.
Removing the Old 3 Prong Cord
- UNPLUG THE DRYER BEFORE CONTINUING! If its plug doesn't fit the socket, this step shouldn't be necessary, but of course you should never attempt to work on an appliance that is plugged in. If the dryer is unplugged, there is no need to check for voltage at the dryer, although a non-contact voltage detector will accomplish this if you want to be extra safe.
- Pull the dryer out until you can easily work on the back.
- The cord should enter the dryer through some kind of connector to prevent strain on the screws where the wire terminates. Loosen any visible screws on this connector and remove the plate that covers the wire terminations. If the old wires are colored, note where the white wire ends.
- Unscrew the fasteners holding the wire to the terminal board and remove the wires. Pull the old cable out through the connector and save it in case you ever move into a home with a 3 hole socket.
- There will be a metal strap or wire fastened to the place where the white wire was, attaching to the frame of the dryer. Remove this strap or wire, and once more, save it for possible use in years to come. Take note of where this strap is screwed to the frame; one of the wires on the new cord will go there.
Removing the 3 Prong Cord and Plug
What Is the Difference Between the White and the Green Wire?
White wire: The National Electric Code (NEC) requires that (with a few specific exceptions) the white wire is the "neutral" one. In other words, it is the grounded circuit conductor wire expected to carry current and that it is grounded at the point of entry to the home (aka at the breaker panel) and nowhere else.
Green wire: The NEC requires that grounds (grounded wires that only carry electricity in a fault situation, when something goes wrong) be either green or bare of insulation, and that ONLY grounds be colored green.
Other colored wires: Any and all other colors are open for use, except that they cannot be used as either a neutral or ground. Typical 240V outlets (as a dryer is) use black and red as the "hot" wires, but any colors except white and green are legally acceptable.
How Do You Remember Which Wire Is Which?
- Tape the wire with a label with "B," "W," and "R" written on it.
- Make a hand-drawn diagram.
- Take a photo with your phone (in today's world that might be the best!).
- Commit it to memory.
Installing the New 4 Prong Cord
- First, make sure that you have A range cord (made for a cooking range) looks very similar and also has 4 prongs in about the same locations. The difference is that a dryer cord has two straight prongs and two bent ones, while a range cord has three straight prongs and one bent one. Make sure that your new cord will fit into the receptacle before installing it (do not plug into a "hot" receptacle; just hold it up next to the receptacle and verify the prongs will fit). the right new cord.
- Push the new cable through the connector. If there is no connector, one should be purchased; the most common type is a 1" romex connector that has a clamp on one side with 2 screws to tighten it and a large nut on the other. Remove the nut, place the threaded portion through the wall of the dryer, and replace the nut.
- With the cable through the connector, it is time to terminate (attach) the wires to the screws where the old wires came out. Black and red terminals will take the outside wires on the flat cable (or on the same colors), and the white wire (center wire on the cable) will attach to the center screw.
- The green wire will attach to the spot where the strap was removed from the frame of the dryer (see above). It does not go on the terminal board where the white wire is, but to the frame. It is a grounding wire for safety and is not used to supply electricity to the dryer. See the pictures for one location for the green wire; your dryer will likely be different, but in all cases the green wire is to be terminated on the frame or body of the dryer and not on one of the three screws on the terminal board.
- Re-attach the cover plate over the wire terminations. It is a wise precaution to turn off the breaker before plugging the dryer in, just in case something is wired wrong. With the breaker off, plug in the dryer and turn the breaker back on.
- If the breaker immediately trips, you have put a wire in the wrong place; turn the breaker back off and find the mistake. If it doesn't trip, turn the dryer on and make sure it operates correctly.
Installing the 4 Prong Cord and Plug
Congratulations: you have successfully changed out the old 3 prong cord for a new 4 prong one that will work in your new home, and it wasn't so hard, was it? Ready to tackle putting in a new light fixture or replacing an old plugin that won't hold a cord in any more? These, too, are easy tasks that almost anyone can do.
Questions & Answers
I bought a new dryer with a four-prong cord. My husband changed the outlet also to be a four-prong. But I don't have a green wire in my wiring. What do I use for the green ground wire? Do I use just the black, white, and red?
You don't. It is not possible to install a four prong outlet using only three wires either legally or safely. Put the three prong outlet back and install a new three-prong cord on the dryer.
As it sits, without any ground to the dryer, there is no way for a ground fault on the dryer (inadvertent connection of a hot wire to the frame of the dryer) to trip the dryer breaker. If it ever happens, the dryer will become energized, and will shock anyone touching it, as well as any form of ground (such as the washer) at the same time. It can also cause a fire.
There are very good reasons for having a ground wire in a circuit, and your new dryer is designed for just such a feature. Without it, the primary safety feature of the entire circuit is missing. Replace the three-prong outlet and follow the link in the article for instructions on installing a three prong cord onto the dryer; this will provide nearly the same safety factor as having a ground wire.
I have four wires red black white and green but where do I put the green wire? It also says ground screw on the outside is that where I put the green wire?
There should have been some kind of connection between the center wire and the frame of the dryer. A jumper wire or a metal strap that was connected to the center terminal.
That jumper connection needs removed and the new green wire goes where it was attached to the frame, or sheet metal, of the dryer. Not the terminal with the white wire - the other end of the jumper.
If your dryer had no jumper the you will need to find a screw somewhere on the frame to attach to. It won't matter much where, as long as it is not one of the red, black or white termination points.
The green wire has to be stretched really tight bending the other three wires. Is this normal?
Sometimes it works that way. One solution is to splice another piece of green wire onto the one in the cord with a wire nut, lengthening it. Other is to strip back some of the outer insulation sheath, leaving each individual wire longer. It probably isn't a good idea to leave any of them as tight as you describe, though.
I'm converting to a four prong cord. My dryer has a "but-in" green wire (with a yellow stripe) already screwed into the frame. It is not part of the new four prong cord. Where do I attach the green wire that is part of the new four prong cord? Do I just overlap it with the existing green cord?
That's the perfect spot to put the new green ground wire - right with the existing one. Just take the screw out, add the new green wire to the existing one and put the screw back in place.
My dryer has the exact setup as the one shown in the photo (grounding metal piece attached where white wire attached & then to the metal frame). I was going to remove the connecting metal piece and attach green wire directly to metal grounding location, however, the green wire was not lot enough. Instead, I unscrewed the unused screw in between the red and white terminal, attached the green wire and shifted the grounding plate to this location. Is there any reason this won't work or is unsafe?
As long as there is no chance at all that the green wire or the grounding strap will come into contact with either red or white wires, it will be fine. I'm assuming that the screw you used is merely to hold the terminal block to the frame of the dryer - that there are no wires to it. Good work!
© 2011 Dan Harmon