Can I convert a 240 motor to 120?


Old 06-06-04, 03:46 PM
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Join Date: Jul 2003
Location: California
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Can I convert a 240 motor to 120?

I have a direct drive furnace blower with a capacitor start motor. The label on the motor says it is a 240V, 1/3 HP, 60 HZ 1025 RPM unit.I connected a 120V cord to the white lead and the black lead and the motor turns but too slowly I think. There are also blue and red leads coming from the motor. The Diagram on the motor shows that they are for slower speeds and there is no evidence that they were ever used.
I want to know if I can convert this motor to 120V and if so how. If I can do it will the existing capcitor work or will it need replaced. The fan was working fine when I took it out and the unit was wired for 240V. Also, since the motor runs but too slowly. (Maybe half speed?) what are the implications of running the blower on the 120V? Am I wasting great amounts of energy? Will it destroy the motor? Am I toying with a fire hazard?
Will someone please help me on this?

Last edited by tightcoat; 06-06-04 at 05:18 PM.
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Old 06-06-04, 08:00 PM
Join Date: Jan 2004
Location: Oregon
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When a motor is operated at too low a voltage, then it can actually draw much more current than when at rated voltage. This can destroy the motor, and yes, this can be a fire hazard.

Some motors can be converted between different voltages. How to do this depends upon the specific motor. This will be described on the motor name plate, or in a description in the terminal housing. If there are no instructions for different voltages, then the only way to convert the motor is to have it rewound by a motor repair shop. The is not economic for such a small motor.

Old 06-06-04, 08:21 PM
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I have to ask....... what is your reasoning for wanting to do this?
Old 06-06-04, 09:49 PM
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Join Date: Jul 2003
Location: California
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I took the blower out of a furnace/airconditioner and since such blowers move a lot of air I want to make a fan out of it. The reason for 120 V is simple versatility. I can use it anywhere.
Thanks for the help.
Old 06-07-04, 09:23 AM
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Join Date: Apr 2003
Location: USA
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Go with what the motor nameplate says. Unfortunately, if it only says 240, you can't use it on 120. It would be very difficult if not impossible to modify the motor to run on 120 without rewinding the motor. You'd be better off to buy a new motor for 120. If it says 120/240, you can run it on 120 when connected properly.

Yes, the white is neutral, black is hi, blue is med, and red is low.

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