No clue how to wire this compressor up for 240V

[Gabor Siklos]

I've had my good ol' trusty Craftsman 20 Gal compressor (model #: 919.176730) you years now. It has a dual voltage motor (MO-6340) but it's always been wired to 120V.

I recently added a 240V line to my garage and successfully changed most of my dual voltage tools to work with that voltage, however I'm having a hard time changing this compressor to 240. I'm attaching the pictures of the "wiring diagram" from the motor and a couple of pictures of the insides of the wiring box. The diagram puzzles me because it looks completely different from the actual wiring. For example I don't see any "orange" wires....

Any help is greatly appreciated.

-Gabor

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[Chris Padilla]

Was there a diagram on the motor plate you removed to expose the wires?

The diagram on the outside of the motor doesn't really say anything about how to wire it but there is a section of it I can't make out.

[Ken Fitzgerald]

Gabor,

The manual says the wiring diagram is located either inside the motor cover or on the motor. Is there a diagram inside the cover?

[Gabor Siklos]

Thanks for taking the time to reply. Unfortunately, there's not diagram on the inside of the cover. It's just plain black. I think the diagram the manual is referring to is the one that I took a picture of, which doesn't make sense to me.

[James Zhu]

On the motor plate, the middle one (BLUE) is L2, the right one(ORANGE) is L1, so the left must be ground.

I would connect black wire (120v) and white wire (120v) to L1 and L2 respectively, leave the green wire as it is.

[Malcolm McLeod]

Find a wiring diagram from the manufacturer! Or, take to a motor shop.

Motor has two windings built for 120V across each. So 4 wires ('leads') come out of motor, 1 from each end of 2 windings. For 120V operation the windings are in parallel; for 240V, they are in series.

When you convert from 120 to 240, 2 of the motor leads should be bonded together - - the 'middle' of the windings. Then the 240V feed get connected to the other 2 motor leads. If you can't ID them to do this, you'll need a new motor soon.

[Von Bickley]

I'm just curious. If you have been using it on 120V for years, and it worked fine, why change it to 220V?

[Rich Riddle]

We discussed wiring a 110 for 220 last fall in the following thread with some diagrams. That might help you.

http://www.sawmillcreek.org/showthread.php?236677-Wiring-for-an-old-motor

[Gabor Siklos]

Thank you everyone for replying. I might just have to take apart the motor to identify the wires coming out of the 2 windings. As to why I'd like to switch this to 240V when it was working fine at 120V: it only works on a dedicated 120V, as it needs all of 15Amps to operate. I only had one dedicated 20A 120V line in my garage, which I decided to switch to 220V because some of my other tools needed it. If I now try to plug the compressor into any other outlet (that is shared), it doesn't work anymore as the power draw is too much for those circuits.

[Rod Sheridan]

The wiring diagram doesn't show it as a dual voltage motor.

What does the nameplate show?

regards, Rod.

[Keith Weber]

Rod beat me to the punch. I was going to ask if you're sure it's a dual voltage motor. Can you show a pic of the nameplate, which shows amp draw, horsepower, etc? If the nameplate only says 120V under voltage, you can't run it on 240V.

[Gabor Siklos]

I don't have a picture of the name plate but I checked it just now and it says 120/240. I can't really take a picture of if since it's totally rubbed out, so I just put a piece of paper over it and "traced" out the indentations for the letters/numbers. The manual also says that these are dual voltage motors.

[Malcolm McLeod]

Please keep in mind that my description above is a simplified one. There will also be wiring to the centrifugal start switch and start winding.

A motor shop may be your best bet.