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2 hp motor wiring help?


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I just picked up a KMG 3 speed grinder with the 2 hp motor. I have an existing 220 outlet on a 50 amp breaker that I use for my welder, is this outlet suitable to use with this grinder? Or should I wire a 30 or 40 amp outlet for it? Also what size wire do I need to use to wire a power cord and switch for the motor?

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If you are going to use the 30 amp plug then you need to have 30 amp wiring, not the suggested 14 ga  it is a hazard to use undersized wiring, just play it safe.

Breakers are set for wire size.  You could easily rewire the motor to run 120 volts, where it will use 17 amps and need a 20 amp/120 volt circuit, if you have to use 14 ga wire then  use the 15 amp 220 volt outlet..

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A breaker is rated to protect the wiring from the breaker to the outlet. The wire between the outlet and breaker should be sized/rated for the full load load plus a safety margin.  Wiring from the plug/outlet to the device (motor/tv/etc) is typically sized for the amount of current the device will use.

I would guess your biggest problem using the 50A outlet will likely be finding a plug that will safely accommodate the small diameter wire you use for your grinder.
If the 50A plug is designed for large wire you don't want to improvise something to make it work with the smaller wire.  The screw terminals may not grab onto and hold the small wire properly.

Your grinder motor should be similar to my 2HP table saw.  It is rated at 240v 7.5A and uses 14AWG from the motor to the plug/outlet (from the factory).  Unless you are going to have an excessively long power cord (over 8ft), 14AWG should be ok from the grinder to the outlet. Personally, I would use 12AWG just to give a bit more safety margin.

I had a similar situation with my table saw.  I wasn't comfortable improvising a 50A plug to work with the 240V 50A RV outlet I had in my workshop. I installed a dedicated 20A 240v circuit using a NEMA 6-20 outlet.  The NEMA 6-20 plugs are designed for the smaller wire in the 10-14AWG range.

Installing a new circuit will give you the added benefit of being able to have the welder and grinder both plugged in at the same time.  If you will be using them both on a project, swapping plugs gets old very fast.

If you do install a new circuit, please make sure to size the wire (breaker to outlet) appropriately for the amperage load and the length of the wire run.
If you aren't comfortable working with electricity, please hire a licensed electrician.  It is cheaper than a funeral bill or a new house.


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