Not all electric motors are created equal. Some motors are single phase, while others operate on three phase current. The same holds true for changing the rotation of electric motors--not all are capable of such wiring, but most are.
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Things you need
- Safety glasses
- Volt ohmmeter
- Wire pliers
- Wire strippers
- Screwdrivers (Philips and slotted head)
- Black vinyl tape
- Plastic wire nuts
Clean those safety glasses before you place them over your eyes. You will have to see clearly to identify those wire numbers or colours. Remove all electric power from the motor you are going to be working on. Confirm that the power is off by turning the volt ohmmeter to volts and placing the leads to the power source. The voltage reading should be zero.
Remove the motor cover using the appropriate screwdriver and set the screws in a place where you will not lose them. This next step depends fully on whether or not this motor is a three-phase current or a single-phase current.
Realise change the rotation on any three-phase motor, whether it is a high voltage or low voltage motor, is the same procedure. Remove the insulating tape or wire nuts from any two of the main power leads that are connected to the motor leads and interchange them. Replace the wire nuts and give each lead a couple of rounds with the black vinyl tape for extra protection. Reapply power and test the motor.
Know changing the rotation on a single-phase motor of 120 voltage or 240 voltage is a little more involved than just interchanging two leads. Different motor manufacturers may have propriety motor windings on smaller motors, but most do not. The majority of low-voltage single-phase motors will have a terminal board just under the termination cover. There should be small numbers embossed on the board. Generally for clockwise rotation, the two power leads will be terminated to number 4 and 7. For counterclockwise rotation, the leads will be connected to 5 and 7. Replace cover, reapply power and test the motor.
Tips and warnings
- Most motor manufacturers will have a small schematic on the inside of the motor cover to confirm the proper termination.
- Check the motor nameplate to be sure that your particular motor can be wired for both directions. Not all motors have this capability.
- Consult with local and state codes before attempting any and all electric work.