How to change the voltage on a century 115/230 volt electric motor

Written by jerry walch Google
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How to change the voltage on a century 115/230 volt electric motor
Large AC electric motors (motors image by Dusan Radivojevic from

Changing the operating voltage is a matter of switching a few wires on the motor's terminal plate. By switching the wires, you change internal wiring for the run windings and the start windings from a parallel hook up for 115 volts to a series hook up for 230 volts. You will find the series and parallel connections on a diagram affixed to the inside of the terminal box cover. The wires are colour coded, and the terminals are numbered.

Skill level:

Things you need

  • Screwdrivers
  • Nut drivers
  • Needle-nose pliers

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  1. 1

    Turn off the circuit breaker to the motor's branch circuit at the service panel. Tape the circuit breaker in the off position. Attach a note to the service panel informing others that you are working on the circuit. Turn off the circuit breaker even if the motor has an on-off switch. Someone could accidentally flip the on-off switch on while you are working on the motor.

  2. 2

    Remove the screws securing the terminal cover plate to the motor's rear end bell. The motor's rear end bell is the end of the motor opposite the shaft end. Loose screws have a way of disappearing, so screw them back in their holes for safe keeping.

  3. 3

    Look at the terminal board and locate the terminals marked #3 and #5. Connect the "Brown" motor lead to the #3 terminal for a 230-volt hookup and to the #5 terminal for a 115-volt hookup. Connect the Brown motor lead to the terminal appropriate for the line voltage being used with the motor. Either a male/female push-on connector or a ring terminal secured to a terminal post by a nut connects the brown wire.

  4. 4

    Connect the red and black circuit wires to terminals #1 and #5 for a 230-volt connection. It does not matter which circuit wire connects to which terminal. With a 230-volt branch circuit, both wires are hot wires derived from separates phases at the service panel, one from "A"-phase, the other from "B"-phase.

  5. 5

    Connect the "Black" and the "White" circuit wires to the #1 and #6 terminals for a 115-volt connection. Again, it does not matter which wire connects to which terminal. The "Black" wire is the "Hot" wire originating from either "A"- phase or "B"-phase at the service panel. The "White" wire is the circuit's "Neutral" or "Grounded" wire and connects to the panel's neutral bar.

  6. 6

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

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