# 120V vs. 240V operation?



## nctoxic (Apr 8, 2012)

In my looking and learning phase of planning to obtain a vertical mill, I see that some new ones come pre-wired for 120v, but can be easily changed to 240v.  I assume that's because most folks buying that size(hobby) already have 120v, and may not want to re-wire for 240v.
Is there any difference in the way a motor performs on 120v.vs. 240v?  I realize the amp draw is twice, but does that translate to cooler/ warmer operation, or is one way smoother running than the other?  In other words, would there be an advantage to using 240v instead of 120v?
I'll save the 3 phase vs. single phase questions for another time.
Thanks,
Tim,,,


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## pdentrem (Apr 8, 2012)

It is more of a hp issue than better running. It is easier to run 2hp and higher on 220/240 than on 120. 

The wire size with its fuse is the limiting factor. 1hp equal 750 watts plus all loses on top of that. 15 amp 120 volt wiring is rated 1800. Sounds like a lot but you will heat your wires if running 2hp for a long period of time. Most people will go 220/240 if running 1.5hp and above.


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## nctoxic (Apr 8, 2012)

So it sounds like y'all are saying that if I bought a new Grizzly 1 1/2 hp milling machine that was pre-wired to 120v that it would be smart to re-wire it to 240V?  I'm just trying to sort this out in my feeble mind.


Thanks.


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## Hawkeye (Apr 8, 2012)

I've had no problems running a 1 1/2 HP mill on 120 volts - and that's on a 15 amp circuit. Never had a slow start or had a breaker trip. Up to 1 1/2 HP, if it ain't bust, don't fix it. If you need more power, you won't get it by reconnecting your motor to 240 V. You would need both a bigger motor and a bigger feed.

Having said that, Blue Chips is right. If your machine is some distance from the panel, you need to at least increase the wire size to cut down on voltage drop _at high current_. When you aren't drawing much current, you aren't dropping much voltage. If you're pulling new wire anyway, might as well go to 240 V.


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## nctoxic (Apr 9, 2012)

Thanks all.  If, or when, I get to that point I'll just pull a 240 dedicated line from the subpanel.  It's only about 20 feet away and the walls are open studs right now.  I already have 10ga wire and a 30amp breaker, so might as well wire it for possible up grades in the future.

Tim,,


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## wineslob (Apr 9, 2012)

nctox said:


> Thanks all. If, or when,* I get to that point I'll just pull a 240 dedicated line from the subpanel.* It's only about 20 feet away and the walls are open studs right now. I already have 10ga wire and a 30amp breaker, so might as well wire it for possible up grades in the future.
> 
> Tim,,


^^^^^^^^^^^^^^^^

:thumbzup:

Smart move. 1.5 HP is equal to 20 amps on a 120V circuit, in general. Cut that in half when on a 220V circuit. Save yourself some headache.


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