Changing an Electric Dryer’s Power Cord from a 3-Prong Plug to a 4-Prong Plug
Q: We recently purchased our first brand new house and we moved in last night. When I tried to plug in my dryer the outlet is different than my dryer cord. My dryer cord has 3 prongs and the outlet has 4 holes. Should I change the outlet or the dryer cord and how do I do this?The 1999 edition of the NEC® first introduced the requirement for a separate ground wire for ranges and dryers. This is also in the 2002 edition as well as the current 2005 edition. This is in Article 250 and specifically section 250.140.
A: Congratulations on the purchase of your first new house. This is a question I receive a lot. You CANNOT change the receptacle (outlet), this is a National Electrical Code® (NEC®) violation. You need to change the cord on your dryer. You need a 4-wire dryer cord and you can get one of these at Home Depot, Lowe’s or your local appliance store for about $15.00.
All dryer and range receptacles installed after 2000 are required to be the 4-wire type. This would require the 4-wire cord. All dryer and range receptacles installed before 2000 are the 3-wire type. If a 3-wire receptacle goes bad, you are permitted to install a new 3-wire receptacle. However, if the cable for the 3-wire receptacle goes bad or if you change the location of your 3-wire receptacle, you are required to upgrade to the new and safer 4-wire type.
Dryers and ranges are not sold with a particular cord attached because of this requirement. When you purchase a new dryer, the appliance store will ask if you want a 3-wire or a 4-wire cord. Both cords are rated 250 volts and 30 amps as are all household electric dryers.
The tools you will need for this installation are:
- 1 – phillips screwdriver
- 1 – standard screwdriver
- 1 – 3/8″ nutdriver
- 1 – 5/16″ nutdriver
- 1 – 1/4″ nutdriver
Lets get started
To change your dryer cord from a 3-wire to a 4-wire you first need to disconnect the old dryer cord. To do this make sure your dryer is unplugged and open the access panel cover on the back of the dryer.
This cover is all different sizes and shapes depending on the manufacturer of the dryer, but it is typically very close to where the cord enters the dryer. The cover is typically held in place with 1 – 4 screws. See image below of a Maytag Performa dryer access panel.
With the cover open you will see a terminal block with three wires. Black on one end, white in the middle and red on the other end. Use your 3/8″ nutdriver to remove the nuts or a phillips screwdriver to remove the bolts (depending on your dryer) and remove each dryer cord wire from the terminal block. When you remove the nuts or bolts, be careful not to drop them down into your dryer.
Click to enlarge
Now you need to disconnect the bonding jumper on your dryer. The bonding jumper is either a metallic strap (typically copper or copperclad) or a green wire that is connected between your dryer’s neutral (white wire) terminal and the green ground screw connected to your dryer’s frame.
Removing this bonding jumper is an extremely important step when changing from a 3-wire to a 4-wire cord toprevent electrical shocks when touching anything metallic on your dryer.
If you removed a ground wire instead of a bonding strap from the neutral terminal, you need to connect this ground wire to your dryer’s frame.
Loosen the screws at the connector and pull the cord out. Now thread your new cord through the connector and tighten down. This only needs to be snug do not over tighten. Sometimes the old connector will work with the new cord and sometimes not. If not, your new cord will include a connector that you may use.
To hook up your new 4-wire dryer cord, connect each wire to the dryer’s terminal block matching color for color (white to white, black to black and red to red). Connect the green wire to the green ground screw on your dryer’s frame.
Replace the access panel cover and your new 4-wire dryer cord is installed.
You cannot convert 3 wire to 4 wire.You will have to buy 4 wire cord.Which will have 4 wires to connect.In the wire there will no red wire.In 4 wire cord there will be red wire.There is no difference in voltage, only 4th red wire is additional.thats it.
