Compressor motor, 1phase or 3 phase?

[Norcal]

My attitude is if 3 phase is available, use it, the OP is fortunate to have it in the shop.

 

[rlitman]

You're right about the VA <> Watts, but a close enough assumption for apples to apples comparison without actually doing live, clamp meter testing, or digging up the power factor data.

Close enough when calculating ampacity and breaker size. Not close enough by a long shot when calculating energy cost.

 

[KenC]

My attitude is if 3 phase is available, use it, the OP is fortunate to have it in the shop.

agree! I have the same 3ph 240, wild leg. Forget the useage savings as they will not be very big. The real difference in the install is wire size somewhat offset by needing more conductors. I know some don't like it, but the conduit is my ground. I use compression connectors as I thing that makes a better electrical connection between sticks of pipe that setscrew.

But the big thing IMO is the simplicty of the motors for long term use. No caps to blow, no centrifigal switch to fail, just wire! Just be sure to provide quality overload protection as most (all?) 3phase stuff doesn't have onboard temp protection.

 

[Norcal]

agree! I have the same 3ph 240, wild leg. Forget the useage savings as they will not be very big. The real difference in the install is wire size somewhat offset by needing more conductors. I know some don't like it, but the conduit is my ground. I use compression connectors as I thing that makes a better electrical connection between sticks of pipe that setscrew.

But the big thing IMO is the simplicty of the motors for long term use. No caps to blow, no centrifigal switch to fail, just wire! Just be sure to provide quality overload protection as most (all?) 3phase stuff doesn't have onboard temp protection.

If it is 240V 3Ø it always has a high leg.

 

[KenC]

If it is 240V 3Ø it always has a high leg.

Yeah, just makin' sure that it was known to be 240 not 208/120.

If anyone has the same, be sure to mark the high leg on all the panel locations! DAMHIKT.

 

[TractorJeff]

You guys are fun! Didn't anyone ever think of how his wattmeter works? They measure off from 3 legs. The one on your house is the same way except it measures off from 2 legs so you want to balance the 2 legs in your panel to get USEFUL work out of ALL the electricity you are paying for! For the OP, he should use a 3 phase motor to get ALL the useful work out of the Power he is paying for.
As far as VA verses KW use any number between .68 and .82 if it really bugs you but like Mack said, basic cost calculations, his numbers are close enough!

 

[Norcal]

Yeah, just makin' sure that it was known to be 240 not 208/120.

If anyone has the same, be sure to mark the high leg on all the panel locations! DAMHIKT.

Testing instruments are made to avoid that very problem.

It's code that the high leg be marked orange and in the B phase lug of a panelboard. It's one of the few places the NEC specs a color code.

NEC art. 408.3(E)(1)

 

[dkmc]

It's gonna be 3 phase because the 1phase "3"HP motor my buddy had is really a 1/3HP
motor! (After you scrape off the oil/dust/grease)
Thanks, it's been a trip...

 

[twinklerai]

I would go with the 3 phase for sure.

 

[sberry]

All this to be able to tell the difference between a 1/3 and a 3 hp?