An electric dryer requires a dedicated 240-volt, 30-amp circuit wired with 10/3 NM-B cable for all new circuit installations. The 10/3 designation means three insulated 10 AWG conductors (black hot, red hot, and white neutral) plus a bare copper ground wire. This 4-wire configuration satisfies the NEC requirement under Section 250.140 that all new dryer circuit installations use a separate neutral and ground conductor, which is why modern NEMA 14-30 dryer outlets have four prongs rather than the three-prong NEMA 10-30 outlets found in older homes.
Why Electric Dryers Need a Neutral Conductor
Unlike most 240-volt appliances that operate on two hot conductors and a ground only, electric dryers also require a 120-volt neutral to power the electronic controls, timer motor, internal light, and buzzer. The 240-volt heating element uses both hot conductors. The 120-volt systems use one hot and the neutral. This dual-voltage requirement is why the cable must be 10/3 (three insulated conductors) rather than 10/2 (two insulated conductors) for all new dryer circuit installations.
Replacing an Existing 3-Wire Dryer Outlet
If you are replacing a worn 3-prong NEMA 10-30 dryer outlet on an existing unmodified circuit wired with 10/2 NM-B, the NEC 250.140 exception permits continued use of the existing 3-wire wiring with a replacement 3-prong outlet. The code does not require rewiring to 4-wire standards when replacing an outlet on an existing circuit that has not been otherwise modified. However, any new circuit run for any reason must meet current 4-wire standards using 10/3 NM-B.
Breaker and Outlet Requirements
The dryer circuit breaker must be a 30-amp double-pole breaker, occupying two slots in the panel and providing 240 volts across its two hot terminals. A single-pole 30-amp breaker delivers only 120 volts and is incorrect for a dryer circuit. The outlet for new installations must be a NEMA 14-30R receptacle (4-wire, 30-amp). The dryer power cord sold separately must match: use a 4-prong NEMA 14-30P cord for a NEMA 14-30R outlet, or a 3-prong NEMA 10-30P cord only for existing NEMA 10-30R outlets.
Run Length and Sizing
For dryer circuits up to 75 feet from panel to outlet, 10 AWG wire handles the 30-amp load with acceptable voltage drop. For laundry rooms more than 75 feet from the panel, upsizing to 8 AWG wire eliminates voltage drop concerns and ensures the dryer heating element receives full voltage on every cycle.
IB Lighting carries 10/2 and 10/3 NM-B Romex from Southwire and Cerrowire in 50-foot and 250-foot spools. Browse our wire and cable selection. Free Freight Insurance Included on every order. Call (800) 674-9019 for contractor pricing.