The Difference in Wiring a 120 and 240 Motor

Electric motors in homes require either 120 volts or 240 volts.

120 Volt

Dual-voltage motors may be wired for either voltage. The motor wire connections are different for all three types and the motor branch circuit devices and wiring are specific to 120 volts or 240 volts.

The motor nameplate will specify the motor requires 125 volts. The wiring connections will include one hot wire, one neutral wire and one ground wire. The motor disconnect device, motor controller module and circuit breaker will be single pole devices which operate only on the hot wire.

240 Volt

The voltage specification on the motor nameplate will be 250 volts. Current is supplied to the motor through two hot wires. A ground wire provides short circuit protection and there is no neutral wire used. The motor disconnect, motor control module and circuit breaker are two pole devices that operate on both hot lines.

Dual Voltage

Dual voltage motors have a nameplate specification that reads as "125/250 Volts." Either 120 volt or 240 volt current is supplied to the motor using one hot and one neutral wire or two hot wires and no neutral respectively depending on which voltage is used. The wiring for the motor's internal windings must be changed for each voltage according to the motor wiring diagram supplied with the motor -- often on the inside of motor's wiring box cover. The motor disconnect, control module and circuit breaker are single- or double-pole devices depending on the voltage supplied.

About the Author

Michael Logan is a writer, editor and web page designer. His professional background includes electrical, computer and test engineering, real estate investment, network engineering and management, programming and remodeling company owner. Logan has been writing professionally since he was first published in "Test & Measurement World" in 1989.