How to Rewire a 110V Motor to 220V

Alternating current (AC) motors are dual-voltage motors. Induction start-induction run, capacitor start-induction run or capacitor start-capacitor run motors are all designed to run on two different voltages. They have two sets of run windings and two sets of start windings that are connected in parallel or in series depending on whether they are being operated on the lower or higher voltage. To switch the windings from parallel to series, to switch between the low-voltage configuration and the high-voltage configuration, as a rule, is simply a matter of changing a few connections on an easily accessible terminal plate.

Turn off the motor branch circuit's circuit breaker. Lock the circuit breaker panel to prevent someone from unknowingly turning the breaker back on while you are working on the motor or tape over the breaker and attach a note warning others that the circuit is being worked on. Safety should be your first concern when working with electricity.

Locate and remove the terminal plate cover plate. Remove the screws securing the cover plate using the screwdriver. On small AC motors, this terminal plate is usually located on the motor's end-bell opposite the end-bell where the shaft exits the motor. Large AC motors have a terminal box located on the side of the motor housing instead of a terminal plate located on an end-bell.

Check the motor winding connections diagram found on the back of the terminal plate cover. Diagrams can become illegible with age but the terminals are numbered or colour-coded based on the National Electrical Manufacturers Association (NEMA) Standard Color Code for Motors.

NEMA Standard Motor Terminal Color Coding Terminal number Colour 1 Blue 2 White 3 Orange 4 Yellow 5 Black 6 No colour assigned 7 No colour assigned 8 Red P1 No colour assigned P2 Brown

Connect the motor for high voltage. Connect L1, the black, or "Hot," circuit wire to terminal No. 1. Connect L2, the white, or "Neutral," circuit conductor to terminals 4 and 5 or terminals 4 and 8 depending on the desired direction of rotation. Connect terminals 2, 3 and 8 together for counterclockwise (CCW) rotation or connect terminals 2, 3 and 5 together for clockwise (CW) rotation. These connections are made with either push on terminals or small nuts. In the case of push on terminals, use the needle nose pliers to make up the connections. In the case of studs with nuts, use the nut drivers to remove and replace the nuts. Nut drivers have a hollow shaft, allowing the stud to slip up inside the shaft.

Connect the motor for low voltage. Connect L1 to terminals 1, 3, 6 and 8 and L2 to terminals 2, 4, 5 and 7 for CCW rotation. Connect L1 to terminals 1, 3, 5 and 7 and connect L2 to terminals 2, 4, 6 and 8 for CW rotation.

Replace the terminal cover plate and turn the circuit breaker back on.

Things You'll Need

  • Motor connections diagram
  • Screwdrivers
  • Nut drivers
  • Needle-nose pliers
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About the Author

Based in Colorado Springs, Colo., Jerry Walch has been writing articles for the DIY market since 1974. His work has appeared in “Family Handyman” magazine, “Popular Science,” "Popular Mechanics," “Handy” and other publications. Walch spent 40 years working in the electrical trades and holds an Associate of Applied Science in applied electrical engineering technology from Alvin Junior College.