120 volt vs 240 volt pump

Bob in Oakboro · Oct 6, 2012

I am about to buy a 3/4hp pump to aerate our pond. I can buy either a 120 volt pump or a 240 volt. The 240 volt is priced about 150 dollars more than the 120 volt. The gpm is the same. Is there any reason to pay more for the 240v pump. I plan to run this unit 10-12 hours per day.

Walt Davies · Oct 6, 2012

Cost the 240 will cost less two run because it runs on the full cycle rather than half.
Walt

Bob Bancroft · Oct 6, 2012

I have no idea why the big difference.
Most of the motors I have can be set either way. Back when we first wired this place, my electrician impressed on me how much more efficient it is to run things on high voltage. Voltage drop on a long cord is less of an issue.

buickanddeere · Oct 6, 2012

How far from the pump, back to the main electrical panel? Size of wire out to the pump?
Would normally recommend 240 but for the difference in price.
You will notice the lights dimming more with the 120V pump, if the lights and pump on the same main line in the panel.
No technical reason for the price difference.
240V pump will require a two pole gfi breaker.

CAROGATOR · Oct 6, 2012

Check prices in a couple more places.

Janicholson · Oct 6, 2012

Help me understand what you mean. I teach electricity electronics, and the voltage on either 110 or 220 are identical on a scope. No 1/2 cycle is in any way evident. the Peak to Peak voltage is twice as high on 220. About 155 to 165 volts on 110, and 220 will have Peak to Peak at 310 to 330. there is no lost or skipped phase elements. Jim

Rick Kr · Oct 6, 2012

Assume you are running some type of fountain if you need 3/4hp. Most motors I have taken apart you can wire 120 or 240 on the endplate.

I aerate my pond with a 1/4hp air pump. Mine truly aerates from the bottom of the pond, no fountain. I couldn"t justify the price to drag copper wire to my pond, too far away. Instead I have two separate ponds with air line underground back to my barn and keep the air pump inside the barn out of the weather.

Rick

Texasmark1 · Oct 6, 2012

Say what?

Both are 50-60 Hz (Cycles per second for us old salts) which alternate from a max positive to a max negative value at that rate. Difference is the transformer hanging on the light pole. 120 only uses half the winding....center tap to one side, whereas 240 is the whole winding.

Running distances, the losses which are non-productive are line current losses. So if it takes a certain amount of volt-amps to run a device, the lower the amps, the lower the loss, and the smaller the wire you can use to get the job done. And then there is power factor, but that isn't part of the line loss equation, just the power company's ability to sell you power...VI Cosine the phase angle.

Mark

Don't believe me? Why do cross country power lines run 66,000 volts or so?

Russ from MN · Oct 6, 2012

Most any 3/4 hp pump I have ever seen is either, try another source. 220 is better.

LJD · Oct 6, 2012

There is no difference in efficiency. The difference is - you can use smaller wire if you choose the higher voltage pump. That may or may not matter to you. Either way - the total electric use is the same.

A typical 3/4 horse pump:

120 volts - max amps is 6.7. Max watts - 724
100 foot wire requires 14 gauge copper.
200 wire requires #10 gauge copper.

240 volts - max amps 3.4 per wire (two of them). Max watts 734.
100 feet of wire requires 14 gauge copper
200 feet of wire requires 14 gauge copper

By the way, I would not ues 14 gauge wire in anything. I used 12 instead. Regardless - the 14 gauge works as stated with a 3% max voltage drop.

John T · Oct 6, 2012

Sure you wanna stick to that story Walt?? Either 120 or 240 single phase utilizes the entire sine wave peak to peak plus to minus. My very first job as an electrical engineer was with the Century Electric Motor Company where I learned as much (more actually) as I did all through engineering school about AC Motors and theory. Of course, I've slept since then lol and a body is never too old to learn, so if youre onto somethign brand new I never was aware of please enlighten all of us.....

Take care Walt n God Bless

John T

John T · Oct 6, 2012

Bob, the 240 volt motor will only draw half the current as the 120, but since the voltage is doubled and watts is volts x amps (at Unity Power Factor at least) ITS GONNA COST THE SAME TO OPERATE AT EITHER VOLTAGE notwithstanding any I Squared R heat losses in conductors to the motor etc. When I did industrial electrical design we preferred higher voltages, and of course, three phase motors if much over 5 HP, because we wanted to dissipate the energy we were paying for in the motor to produce work versus wasting energy in the conductors.

John T

Geo-TH,In · Oct 6, 2012

Save yourself $150.

massey 333 · Oct 6, 2012

An interesting question,John.On a dual voltage motor,230-460 single phase,how do you get 460?Dad bought some equip.in the late 40s that way and now for my grain setup I'am seeing some new motors rated that way.10-15HP

paul · Oct 6, 2012

A 240 is a very tiny bit more efficient. Not so's you'd recover $150 tho. Not sure you'd even recover 10% of that on such a small motor....

The 240 can use a smaller set of feed wires - how long of a run from your power to where the pump will be? If the wires are already there, what is there (wire size, number of wires, length of run)? This might be very immoportant if you need to run several 100's of feet, or it might not mean anything. As well, do you need 120 out there for some other reason, then you need a 4th wire for the 240 - don't know what you have.

In general a 240 is a little better, but that is quite a price difference, don't know that it's _that_ much better!

--->Paul

Will Herring · Oct 6, 2012

(quoted from post at 18:56:25 10/06/12) An interesting question,John.On a dual voltage motor,230-460 single phase,how do you get 460?Dad bought some equip.in the late 40s that way and now for my grain setup I'am seeing some new motors rated that way.10-15HP

I *think* that you accomplish getting 480 single phase wiring hot-to-hot instead of hot-to-neutral (which would get you about 277V)... Never messed with it, but have heard about it. But you'd have to have 3-phase 480 service to start with to do that, methinks?

John T · Oct 6, 2012

We didnt run many motors on 460 single phase in any of the many places I designed for HOWEVER sure its possible to wire a single phase motor dual voltage 230/460 same as they are wired for 115/230.

We did however, run a bunch of 460 3 phase in our industrial complex, so if you needed some 460 single phase you simply took off one 460 volt transformer bank if it was a Delta configuration or one leg to another leg if it was a Y configuration. IE if you have a 460 three phase service its easy to get 460 single phase

But if you only have 230 single phase in your shop and need 460 single phase, then you need to use a dry step up transformer, 230 in 460 out. But a transformer has a lot of heat losses ya know so you dont get the power out you put in, some is lost to heat.

John T

oliver power · Oct 6, 2012

I had a brand new 110V well pump which would not run off a 3500W generator. Swaped it for a used 220V pump, which worked just fine.

John T · Oct 6, 2012

The service you "heard about" is known in the trade as 480 Y 277 Volt Three Phase Four Wire. I used to specify it all the time for industrial applications that requiure a lot of 480 3 phase for motors and HVAC and then we used the 277 single phase for lighting. Its 480 volts line to line and 277 volts line to Neutral.

Hope this helps

John T

Walt Davies · Oct 6, 2012

You must have missed school that day John.
120 uses only half of the sine wave because the neutral wire goes to ground and as one knows the ground can't send the other half back.
Walt
PS learned that in basic electricity

massey 333 · Oct 6, 2012

Thank you John,it's been too many years since dads welders and motors were wired up 440-1.The min.charge is so great for 3 phase plus can't use single off it.A O Smith-Century has come with some new 230-460 motors we are thinking on.

Jon Hagen · Oct 6, 2012

120V uses 1/2 of the secondary 240V transformer winding.
Neutral is the center tap on that 240V winding. From either end of that 240V secondary winding to neutral / center tap, is 120V, but still full sine wave. Connecting to both ends of that 240V secondary winding and not using the nuetral leg gives you 240V, also at full sine wave.

MarkB_MI · Oct 7, 2012

You gotta calculate the cost of wiring, since you"ll probably need to go up a size with the 120 unit. There"s a significant price differential between 12 and 10 gauge UF.

MarkB_MI · Oct 7, 2012

You gotta calculate the cost of wiring, since you"ll probably need to go up a size with the 120 unit. There"s a significant price differential between 12 and 10 gauge UF.

120 volt vs 240 volt pump

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