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120 and 240 Volt Motor Wiring


By Dave Rongey - Summary:

How to Wire a Motor for 240 Volts when the Motor is Designed for 120/240 Volts for Better Efficiency


How to Wire a 120/240 Motor for 240 Volts

Electrical Question: When wiring a 120/240volt motor is there any significant difference in power consumption 120v vs 240v, and any lose or gain in motor longevity?

This electrical question came from: Bruce , a Homeowner from Yosemite, CA
See more about Home Wiring for California

Dave’s Reply:
Thanks for your electrical question Bruce .

Wiring a Motor for 240 Volts

Motors that are Designed for 120/240 Volts

  • Most electric motors have a wiring junction box, typically on the rear of the motor on one side. This is where the cord or conduit attaches. The junction box has a cover plate in place to protect the wiring and connections. The motor will also have a name plate with information such as the make, model,  horse power rating, voltage, amperage, etc.
  • If the motor has a dual voltage capability then it will state 120/240 volts, and there will be a wiring configuration or wiring connection diagram which will explain the wiring configurations for each voltage. In some cases it may be a matter of relocating two wires with spade terminals or ring tongue terminals, and then the LINE or power source wires will attach as described.
  • With larger motors there may be a larger junction box with lead wires that are identified with numbers or letters which will be identified by the wiring diagram of the specific motor.

The Benefits of Wiring a Motor for 240 Volts When it is an Option

The Advantages of a 240 Volt Motor
Bruce, thanks for your question from Yosemite,CA – which is one of my favorite places to stay.  I just love Yosemite! Specifically Cabin 819 in Curry Village near the Awahnee Hotel which is the absolutely best place to be for Thanksgiving or Christmas.

The advantages of wiring a 120/240 volt motor for 240 volts is as follows:

  • A balanced electrical load which may save on electricity compared to an unbalanced electrical load.
  • Faster starting power. 240 volt motors will have a stronger start compared to a 120 volt motor.
  • Longer life may be found due to a stronger motor, where as 120 volt motors may heat up more which may affect the over all lifespan of the motor.
  • Stronger performance will definitely be noticed, especially when using equipment such as a table saw etc.
  • Smaller circuit wiring size may be use in some applications because a 240 volt motor requires less amperage per leg compared to the single power leg of a 120 volt motor.

IMPORTANT

  • Not all electric motors may be wired for 240 volts. Consult the name plate information that is found on the motor, or consult the information from the manufacturer to see if the motor may be wired for a higher voltage.
  • In most applications the wire connections or terminations will need to be changed as well to reflect the voltage that the motor will be connected to as specified by the manufacturer of the motor.

RESOURCES

Electrical Wiring

For more information about 220 Volt Wiring Diagram
220 Volt Wiring Diagram
220 Volt Wiring Diagram
Wiring 220 Volt Electrical Outlet
Home electrical wiring includes 110 volt outlets and 220 volt outlets and receptacles which are common place in every home. See how electrical outlets for the home are wired.

This link is helpful as a Homeowner
Do-It-Yourself Electrical

How to Wire a Motor for 240 Volts




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2 Responses to “120 and 240 Volt Motor Wiring”
  1. Ed Lawlor says:

    I have a residential unit with a fan coil wired for 208/230 volt motor. I am replacing the unit with a 120 volt EC motor. Can I use the existing wiring circuit (use one leg) to power the new equipment? Did not want to increase customer costs with new 120 volt circuit home run.
    Thanks.

    • Dave Rongey says:

      Hi Ed,
      If the existing circuit is dedicated, and the amperage is within the specs of the new motor then it can be converted to be 120 volt at the panel and at the motor connections. However, you should understand that the 120 volt motor will require more amperage, and this may affect the performance of the unit. In cases such as this it is best to replace the motor with one of the same specs to make sure the unit is left in OEM condition. This may keep you out of a potential problem with the customer in the future, plus you will not have to make any wiring changes. ;-)
      I hope this helps,
      Dave


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