Electrical Cable Specifications

• The diameter of a length of electrical wire is denoted by its American Wire Gauge (AWG), a standard that has been in existence in North America since 1857. Larger diameter wires have lower gauge numbers and are capable of conducting more current than smaller diameter wires. The AWG is usually stamped on the sheathing of a length of electrical cable along with another number that specifies the number of conductors enclosed in the sheathing, not including the ground wire. Thus, a length of 12-gauge, 2-conductor cable that includes a ground wire -- suitable for wiring a light fixture -- would bear the stamp "12/2."
  
  

Dryers Need Larger Wires

• Electricians use 14- or 12-gauge cable to wire most residential light and outlet circuits, but this size wire would quickly overheat if it were used to power a dryer. Every electrical conductor, no matter how efficient, has some resistance to current flow, and the energy of this resistance is dissipated in heat. Resistance increases with decreasing wire size, so passing the large current that a dryer draws through 12-gauge wire can produce enough heat to melt the insulation, the outlet casing and the plug. Moreover, large currents pass less efficiently through smaller wires than through larger ones.
  
  

Dryers Need an Extra Hot Conductor

• Most residential appliances operate at 110 volts, but large ones like dryers and electric stoves operate at 220 volts. Residential panels have two hot buses, each at a voltage of 220 volts relative to each other and 110 volts relative to ground. Small appliance circuits draw power from one hot bus, but a dryer draws power from both. Therefore, the cable supplying the dryer must have an extra hot wire. Dryer cables thus have three conductors plus a ground. The two hot wires are sufficient to power the dryer, but the cable also includes a neutral wire, needed for powering auxiliary equipment in the dryer.
  
  

Dryer Cable Specifications

• The type of cable you need for your dryer depends on the maximum current it draws. For most dryers, this maximum is 20 to 30 amps, and the appropriate cable for these dryers is 10/3. Some dryers, however, need more current -- up to 50 amps -- either because they are larger or because they are designed to dry clothes more quickly. For these, the appropriate cable to use is 8/3. The current rating on the dryer is specified on a plate located near the electrical terminals. The size of the circuit breaker that controls the dryer circuit should match the dryer's current rating.