Cost Effective

[thryll]

I am wondering what benefit would you get from running a 1hp motor at 208vac vs 115vac. A customer has been told it would be cheaper to run the motor off of 208vac. The customer is having no problem running the motor off of 115.
two questions
Will the motor run cooler?
Would it ultimately be cost effective to swap to 208vac?

 

[OperaHouse]

You could save a little in line losses and the motor might start a litte easier if it was a long run. If there aren't any problems now, I don't see how the effort would be worth it.

 

[jraef]

It's just a common misconception. If it were 208V 3 phase vs 115V single phase, then there would be a significant difference. But if the choices are both single phase, the power consumption is in watts, not volts. Volts go up, current goes down, but watts stay the same. Line losses are the only difference but relatively insignificant on something this small.

In fact, 1 phase motors are designed for 230V 1 phase because technically there is no such thing as 208V single phase distribution so they don't design for it. What you have is 2 phases off of a 3 phase distriution panel (the phase angles are 120 degrees instead of 180). So at 208V, although still within tolerance for the motor, you will be pulling MORE current than if operating at design voltage, so the motor would run warmer than at 115V.

JRaef.com
Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[LionelHutz]

People think less current means less power. However, the power out at the shaft is always and power out = power in - losses so it's only the losses that affect the running cost.

I also agree with JRaef, single phase motors are typically designed for 115V/230V, so they're not built for 208V. There's also no 208V single phase. If they have 208V then they have 3-phase power in the building so put in a 3-phase motor which should be more efficient and require less maintenance.

 

[dpc]

208 V single-phase certainly exists, even if you have a three-phase service.

Single-phase motors nameplated for 200 V may be hard to find, but 208 V single-phase is often used for other types of loads.

As far as the OP question, though, I agree that there is little to no benefit of changing from 120 V to 208 V, even if you could find a suitable motor.

 

[thryll]

I would like to thank everyone for there responces. These were my thoughts exactly.

 

[SteveKW]

It's cheaper in the initial installation.
The higher voltage means you can buy a smaller wire size and related controls.

 

[dpc]

StevekW,

You're right, assuming the two motors are roughly the same cost - but the 200V motor may cost more than the 110 V motor.