what is better 110 or 220 if the appliance can be wired for both.

For single phase motors, if it draws 10 amps @120 volts, it draws 5 amps @

The devil is in the details, but I doubt the difference will amount to much.

Power lost in the wiring is I^2*R, which is probably what the electrician has in mind, but the wire used in the two cases won't be the same, so won't have the same R.

I'd probably go with the 220 (240?) if it draws more than a kilowatt when operating.

Electric motors always run more efficiently at the higher voltage and start better also. Less current draw during startup also.

Agreed, and more efficency in motors can lead to longer service life if that's worth anything.

Why?

and start

Hi,

Hi, Why? Power factor!

You will not save, in either case. Same number of watts used.

The advantage with 220 is that you can use smaller wire to connect. So you get some upfront savings.

Higher voltages also travel farther down the wire with less loss to heat.

Since the amperage draw is is lower, there will be slightly less energy loss to warming the wires. But the difference is insignifigant.

Less drop in the supply.

Do explain!

Hmmm, Just simply KVA vs. Wattage for a given load. The close each other, the power factor is approaching unity(1). I don't want to go into details. Class room stuff.

Explain, please.

Yes, we've already discussed I^2*R drops, but those depend on the wire used, too. The poster to whom I responded seemed to imply there was more to it.

And that's not really the efficiency of the motor, per se, but the efficiency of the delivery system.

Indeed.

We know what power factor is.

But why do you think it's voltage dependent in a fashion that favors higher voltage systems?

I don't see why either 220 or 110 supply will inherently have a lower or higher power factor. The current and voltage should not necessarily have any phase shift differential because of the voltage difference.

On the other hand, winding losses for a given horsepower motor should increase due to a lower voltage and thus a higher current being required, unless the motor has been wound with considerably larger gauge wire. Unless the motor has been designed and built to compensate with lighter parts elsewhere or lower friction elsewhere, it seems that a lower voltage 110 volt / higher current motor would be less efficient.

Smarty

That makes sense. There are I^2*R losses in the motor as well as the feed wiring. I would hope they're not large relative to the work done, though.

Thanks.

I know what power factor is. What's it got to do with this discussion?