# Thread: dual voltage motor - which is better?

1. ## dual voltage motor - which is better?

so I just replaced my 2 HP motor with a new 1 HP motor (an a. o. smith centurion 56Y 1081 1HP if I recall correctly).

It can be wired at 230v or 115v. I left it at 230v (default) because that's what the 2HP was set to and I didn't want to mess with it.

My question is stupid - what's the difference? If it's at 115v does it really use 1/2 the electricity? If so, does it produce half the flow?

So how do you decide what's best for your application?????

I haven't seen anything on the power curves that makes this apparent... thanks for any advice.

2. ## Re: dual voltage motor - which is better?

Power consumption is the same for both settings. 220 is better since the current draw is halved which allows you to use smaller wire and to lose less voltage on long wire runs. Power is roughly voltage X current, so for the same power consumption, if you double the voltage you halve the current.

3. ## Re: dual voltage motor - which is better?

The pump can accomplish this halving of the current by having two windings where they are connected in series for 230V and connected in parallel for 115V. Using a simplistic resistive-only example, the following describes the situation using "R" as the resistance of each winding using Current = Voltage / Resistance and Power = Current * Voltage.

SERIES ........ 230V .................... 115V
Current .... 230/(R+R) .......... 115/(R+R)
Power ... 230*230/(R+R) ... 115*115/(R+R)

PARALLEL .. 230V .............. 115V
Current ... 2*230/R .......... 2*115/R
Power ... 230*2*230/R ... 115*2*115/R

You can see that the total current is half with 230V in series vs. 115V in parallel while the total power is the same. The current in each winding (as opposed to total current) is the same in both cases, 115/R. The voltage across each winding is the same in both cases, 115V.

Richard

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