5HP motor electrical hookup - Woodworking Talk - Woodworkers Forum
 
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post #1 of 6 Old 12-08-2015, 06:24 PM Thread Starter
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5HP motor electrical hookup

I recently acquired a grizzly 5HP table saw. The current male plug that is installed on it (looks like its from manufacturer) is a 3-prong NEMA10-30. In doing some research, that is an older style of dryer plug that used a hot-hot-neutral configuration where, in practice, the neutral was grounded effectively making it hot-hot-ground. Somewhere around 95/96 the switch was made? Anyways...
I have a 2 year old new construction that they put in a 240V receptable in the garage of style NEMA14-30 operating as hot-hot-neutral-ground. I confirmed that is how it is wired.

My question - i'm not sure how I can make the 3-pronged plug work with the 4-pronged outlet. My intuition says if I made a custom adapter I could just wire the NEMA14-30's neutral & ground together and that would work. But I don't have much experience here and would appreciate guidance. I guess I could also run a new wire with the newer NEMA14-30 style, but since the old plug didn't have a true neutral, I don't know where to place it into the magnetic switch, nor does the manual help me.

Thank you!

Last edited by Parabola; 12-08-2015 at 06:32 PM.
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post #2 of 6 Old 12-08-2015, 06:38 PM Thread Starter
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Attached is the receptacle and plug along with the magnetic switch circuit diagram.
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post #3 of 6 Old 12-08-2015, 07:50 PM
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A clothes dryer needs a neutral because it has a 110V fan motor in it. Your 5hp motor doesn't need a neutral. All it needs is the two 110v lines and a ground with heavy enough wiring for the amperage. Actually the motor itself only needs the two 110v lines. The ground is needed to protect you.

The magnetic switch you have illustrated at the bottom would do fine.
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post #4 of 6 Old 12-08-2015, 08:51 PM Thread Starter
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Quote:
Originally Posted by Steve Neul View Post
A clothes dryer needs a neutral because it has a 110V fan motor in it. Your 5hp motor doesn't need a neutral. All it needs is the two 110v lines and a ground with heavy enough wiring for the amperage. Actually the motor itself only needs the two 110v lines. The ground is needed to protect you.

The magnetic switch you have illustrated at the bottom would do fine.
So my first suggestion is sound? Connecting the neutral and ground together as one on the receptacle side? Or do I let the neutral float?
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post #5 of 6 Old 12-08-2015, 09:08 PM
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Originally Posted by Parabola View Post
So my first suggestion is sound? Connecting the neutral and ground together as one on the receptacle side? Or do I let the neutral float?
For a 5hp motor forget the neutral. A neutral is a current carrying line and if you get it connected where the ground is suppose to be you may create a hazard. Connect the body of the motor to the ground. That is all it needs. If your outlet is for 4 wires you can use a four prong plug with your motor but use only three wires. The L shaped prong is the neutral and the more round one is the ground.
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post #6 of 6 Old 12-08-2015, 09:15 PM Thread Starter
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Ok. I will forget about the neutral altogether. Thank you, Neil.
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