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03-10-2010, 01:51 PM   #1
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## Does 240v use less energy than 120v?

Does a 240v air compressor use less energy than a comparable 120v unit?

03-10-2010, 01:55 PM   #2
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I'll take a shot at this:

Volts (pressure) x Amps (size of line) = Watts (energy used)

A 240v/20a device would certainly use more than a 120v/21a device.

Think of it like water:
75 PSI in a 1" pipe uses more Gallons Per Minute than 25 PSI in a 1" pipe.

Right?

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 03-10-2010, 02:07 PM #3 Member   Join Date: Nov 2009 Location: Downriver Michigan Posts: 86 Rewards Points: 75 No... A 240V air compressor has the "potential" to use more energy than a 120V model but that is not always the case. Check the nameplate to see either the watts or the current of the device. As secutanudu mentioned... Energy = Watts Energy = Voltage * Current

03-10-2010, 02:13 PM   #4
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Quote:
 Originally Posted by DownRiverGuy No... A 240V air compressor has the "potential" to use more energy than a 120V model but that is not always the case. Check the nameplate to see either the watts or the current of the device. As secutanudu mentioned... Energy = Watts Energy = Voltage * Current
I agree. A watt is a watt. 2400 watts @ 240 volts is the same as 2400 watts @ 120 volts.
Power is measured in watts.

 03-10-2010, 02:20 PM #5 Member   Join Date: Jul 2009 Location: Sacramento CA Posts: 257 Rewards Points: 250 So if you've got a compressor that is capable of running on either 120 or 240, are you better off running on 120 or 240? I assume the motor would run more efficiently on 240. What do you folks think?
03-10-2010, 02:24 PM   #6
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Quote:
 Originally Posted by secutanudu I'll take a shot at this: Volts (pressure) x Amps (size of line) = Watts (energy used) A 240v/20a device would certainly use more than a 120v/21a device. Think of it like water: 75 PSI in a 1" pipe uses more Gallons Per Minute than 25 PSI in a 1" pipe. Right?
You have to compare the same devices or equipment. In your example you would need a 120 volt device that draws 40 amps not 21 amps.

When you double the voltage the amperage decreases by 50%

A certain motor uses 4800 watts. Wired for 240 volts it will draw 20 amps. Wired at 120 volts it wil dra 40 amps.

Last edited by brric; 03-10-2010 at 02:28 PM.

03-10-2010, 02:26 PM   #7
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Quote:
 Originally Posted by mopowers So if you've got a compressor that is capable of running on either 120 or 240, are you better off running on 120 or 240? I assume the motor would run more efficiently on 240. What do you folks think?
The issue becomes voltage drop and wire size. 240 volt motors can be supplied with lower amperage circuits than the same motor using 120 volts

 03-10-2010, 02:34 PM #8 Just call me Andrew   Join Date: Mar 2009 Location: Albany, NY Posts: 2,265 Rewards Points: 1,020 I stand corrected! I had a feeling it was more complicated than it seemed. __________________ Andrew
03-10-2010, 02:38 PM   #9
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Quote:
 Originally Posted by secutanudu I stand corrected! I had a feeling it was more complicated than it seemed.
No problem. I consider it a bad day if I don't learn something new each day.

 03-10-2010, 02:52 PM #10 Member   Join Date: Jul 2009 Location: Sacramento CA Posts: 257 Rewards Points: 250 Thanks for the replies! Do you think the difference in voltage drop would be significant?
03-10-2010, 02:59 PM   #11
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Quote:
 Originally Posted by mopowers Thanks for the replies! Do you think the difference in voltage drop would be significant?
Depend upon how far the unit is from the elecrical panel and upon the current draw of the compressor.

Let me ask. Do you even have 240 volts available at the location where you intend to use the compressor?

03-10-2010, 03:19 PM   #12
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Quote:
 Originally Posted by brric Depend upon how far the unit is from the elecrical panel and upon the current draw of the compressor. Let me ask. Do you even have 240 volts available at the location where you intend to use the compressor?
I actually have a 240v compressor in my garage already. I just started this thread as a hypothetical question.

My compressor is pretty far from the panel (say 75 feet). The circuit I have is rated for 50 amps and uses aluminum wire, however I replaced the breaker with a 30a breaker as recommended by the compressor mfg.. The compressor draws 17amps I believe. What would be the voltage drop on this circuit? What about if it were wired into a 120v circuit w/ 10-2?

 03-10-2010, 03:30 PM #13 Experienced goon   Join Date: Feb 2009 Posts: 57 Rewards Points: 75
03-10-2010, 03:46 PM   #14
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Quote:
 Originally Posted by mopowers I actually have a 240v compressor in my garage already. I just started this thread as a hypothetical question. My compressor is pretty far from the panel (say 75 feet). The circuit I have is rated for 50 amps and uses aluminum wire, however I replaced the breaker with a 30a breaker as recommended by the compressor mfg.. The compressor draws 17amps I believe. What would be the voltage drop on this circuit? What about if it were wired into a 120v circuit w/ 10-2?
What is Al wire size?
If 17 amps is the draw@240 volts then the draw would be 34 amps @120 volts.
Need the wire size to calculat voltage drop.

03-10-2010, 04:04 PM   #15
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I'm not sure of the wire size. But it would be whatever size needed for a 50amp circuit. I do know that the wire is aluminum. It looks really big to my untrained eye.

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