120 and 240 Volt Motor Wiring
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Should I wire my motor for 240volt or 120volt? The advantages of wiring a volt motor for 240 volts. © By: Dave Rongey |
How to Wire a 120/240 Motor for 240 Volts
Electrical Question: Should I wire my motor for 240volt or 120volt?
When wiring a 120/240volt motor is there any significant difference in power consumption 120volt vs 240volt, and any lose or gain in motor longevity?
This electrical question came from: Bruce , a Homeowner in California.
Dave’s Reply:
Thanks for your electrical question Bruce .
Wiring a Motor for 240 Volts
Application: Wiring an Electric Motor.
Skill Level: Intermediate to Advanced – Best Performed by a Licensed Electrician or Certified Motor Technician.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester.
Estimated Time: Depends on experience with electric motors.
Precaution: Electric motors are best serviced by an experienced electrician or knowledgeable technician. Changes in the wiring of an electric motor should only be made after the electric motor circuit has been identified and turned OFF and Tagged.
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 Advantages of a 240 Volt Motor
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.
More about 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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Old Robbins and Meyers Motor Wiring Diagram
Hi William,
Unfortunately I have not been able to locate a wiring diagram for your Robbins and Meyers motor.
I would suggest visiting the Google Groups page where there is some discussion about Robbins Myers motor wiring.
Here is the link: Google Groups Robbins Meyer motor wiring
I hope this helps,
Dave
Need Wiring Diagram for a Robbins Myers Motor
I have a old Robbins & Myers motor. The plate reads, 110/220, 1725 RPM, frame S204, M/S 4470, SN AC111/94.
There is no wiring diagram. There are 6 leads, all the same color.
They do have numbered clip, 1, 2, 3, 4, 8, 8.
What is the connections to run on 110 volts.
Thanks.
Circuits for Two 120volt Motors
Hi Timothy,
Using a multi-wire 4wire circuit for two 120volt motors would depend on the type of motors that would be connected and the application. However, due to the amperage of the 120volt motors as described, and the possibility of overloading a shared neutral it would be best to install two separate circuits, one dedicated circuit for each motor.
Dave
Can I Wire Two 120volt Motors to a 240volt circuit?
What if I have two 120v motors which operate at 14amps? I cannot run them on a single 20amp circuit.However, I have a 240 volt (4 wire) circuit which can handle much more amperage. If I was to wire one pole of each motor to the neutral and the remaining pole each to a separate hot wire (Having two 120v powers from one circuit) would that power each motor and not bust the amperage limit? Also, will there be any back-EMF effects through the neutral (which is shared)?
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
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.