How to Reverse the Direction of a Single Phase AC Motor

Alternating current motors are either induction start-induction run, capacitor start-induction run, or capacitor start-capacitor run motors. AC motors may be single voltage or dual voltage motors with one or two run windings respectively. The run windings on dual voltage motors, i.e., 110/220 volt motors, are connected in parallel or series depending on the system voltage. The direction of rotation of an AC motor depends on the magnetic polarity of the start winding. Reversing the polarity of the "Start" winding, in relationship to the "Run" winding, reverses the direction of rotation of all single-phase alternating current (AC) motors.

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AC induction motors

Step 1

Turn off the circuit breaker (CB) or unscrew the Edison base fuse(s) protecting the branch circuit feeding power to the AC induction motor that you will be working. Lock the panel closed or tags the breaker or fuses so someone doesn't turn the circuit back on while you are working on the motor.

Step 2

Using a flat blade screwdriver, remove the plate covering the electrical connections on the end-bell of the motor. On larger horsepower induction motors, this may take the form of a junction box similar in appearance to an electrical junction box and cover.

Step 3

Locate the terminals marked T5 and T6 or T8 and reverse the wires attached to those terminals. Fractional horsepower motors uses push on terminals so use the needle nose pliers to pull them off and push them on the opposite terminals. Larger motors use studs with 1/4 or 5/16 inch nuts. Use the appropriate size nut driver to remove and replace these nuts. Nut drivers have hollow shafts so the studs slip up inside them giving good contact with the terminal nuts.

Step 4

Once you have switched the leads to terminals T5 and T6 or T8, squeeze the push on together gently to make sure they're making good contact. Whether you will be switching T5 and T6 or T5 and T8 depends on whether the motor has two start windings or one and whether it's wired for high voltage or low voltage. Motors with one start winding require you to switch T5 and T6, as do motors with two start windings wired for low voltage. Motors with two start wings wired for high voltage require switching T5 and T8 because T6 and T7 connect the two start windings in series for the high voltage connection.

Step 5

Replace the terminal cover and turn the CB on or replace the fuses.