Dryer Electrical Requirements
In most electric dryers, power passes through a conducting element, and the electrical resistance of the element material causes it to produce heat to dry clothing. In order to produce enough heat to dry a load in an hour or less, a dryer requires 240-volt electricity, which is double the voltage supplied to lights and other small appliances. Moreover, the current to the dryer must be larger than that supplied to small appliances. Most dryers draw up to 30 amps when running at full power, but some large or fast-drying ones can draw up to 50 amps.
In the AWG system, a lower gauge number denotes a larger diameter wire. Electrical cable bears a stamp on its sheathing denoting the AWG number as well as the number of conductors, not including the ground wire, encased in the sheathing. Thus, a 12-gauge cable with one hot and one neutral conductor bears the stamp "12/2." Similarly, a 10-gauge cable with two hot conductors and a neutral bears the stamp "10/3." Dryers drawing 30 amps require 10/3 cable, while those drawing 50 amps require 8/3 cable.
The Need for 10/3 Cable
Just as electrical resistance produces heat in an electric dryer element, it also causes the wires supplying the electricity to heat up. Resistance increases with decreasing wire diameter, so the sheathing on 12-gauge cable used in most residential circuits can melt when passing the current necessary to run a dryer. Moreover, cable supplying 240 volt appliances, like dryers, must have two hot conductors, each leading to a separate bus on the electrical panel. Because dryers have auxiliary 120-volt components, dryer cable must also include a neutral wire; 120-volt power is produced between one of the hot wires and the neutral.
Dryers can operate without a ground conductor, and previously included only three wiring terminals for the two hot wires and the neutral. In 1992, the electrical code began to require grounding for all 240-volt residential circuits, and dryers sold after that date include an extra terminal for ground. You can connect an older dryer to a grounded circuit by attaching the circuit's ground wire to the body of the machine with a grounding screw. If you have unground circuitry, on the other hand, you can connect a newer dryer by connecting the dryer's ground terminal to its neutral terminal with a bonding strap.