The electrical outlet for your dryer has either three or four prongs, depending on the wiring of your home. Three-prong outlets are found in older homes, however most local building codes have been changed to require a four-prong outlet. Prior to purchasing a power cord for your dryer, inspect the outlet to determine the type of power cord required for the proper installation of your dryer.
The difference between a three- and four-prong power cord lies in the method of grounding the dryer. Older building codes allowed for appliances to be grounded using the neutral (white) wire. New building codes require appliances to have a dedicated ground wire, resulting in a fourth prong.
The terminal block is the location at which you must install the power cord. Located on the rear of the dryer, the terminal block is protected by a metal plate that you must remove to access the block. All power cords have a red, black and white wire, while four-prong cables also having a green or bare wire. When a three-prong cable is installed, a metal plate is connected from the grounding screw (or rivet in some cases) on the terminal block to the center, or neutral terminal. Four-prong cables do away with the metal plate, with the green or bare wire being connected directly to the grounding screw. If the grounding strap is connected to a rivet, you must bend the grounding strap away from the terminal block, then connect the green or bare wire to the grounding screw.
Although many power cords have the typical red, black and white wires, some cords have two black wires and one white wire. The white wire is always the neutral wire, and must be connected to the center terminal on the terminal block. A black wire must always be connected to the left terminal, and the other black wire or red wire must be connected to the terminal on the right side of the terminal block.