Does 240v Use Less Energy Than 120v? - Electrical - Page 2 - DIY Chatroom Home Improvement Forum
Advertisement


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools
Display Modes
Old 03-10-2010, 03:12 PM   #16
Master Electrician
 
Join Date: Mar 2010
Location: Indiana
Posts: 4,413
Rewards Points: 5,082
Default


Quote:
Originally Posted by mopowers View Post
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.
How old is the circuit? Could it be tinned copper rather than aluminum?
brric is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 03-10-2010, 03:21 PM   #17
Master Electrician
 
Join Date: Mar 2010
Location: Indiana
Posts: 4,413
Rewards Points: 5,082
Default


Quote:
Originally Posted by mopowers View Post
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.
Assuming #4 Al:

VD for 17 amps @240 volts is 0.5 volts or 0.4%

VD for 34 amps @120 volts is 1 volt or 0.8%


Both of these are withinn acceptable limits.
brric is offline   Reply With Quote
The Following User Says Thank You to brric For This Useful Post:
mopowers (03-10-2010)
Sponsored Links
Advertisement
 
Old 03-10-2010, 03:24 PM   #18
Member
 
Join Date: Jul 2009
Location: Sacramento CA
Posts: 258
Rewards Points: 252
Default


Quote:
Originally Posted by brric View Post
How old is the circuit? Could it be tinned copper rather than aluminum?
I guess it could be. I have no idea. How would I tell? The house was built last July in CA if that matters.
mopowers is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 03-10-2010, 03:26 PM   #19
Member
 
Join Date: Jul 2009
Location: Sacramento CA
Posts: 258
Rewards Points: 252
Default


Quote:
Originally Posted by brric View Post
Assuming #4 Al:

VD for 17 amps @240 volts is 0.5 volts or 0.4%

VD for 34 amps @120 volts is 1 volt or 0.8%


Both of these are withinn acceptable limits.
Thanks man. So the difference would only be 0.4% I'm guessing I would never see that in my wallet.
mopowers is offline   Reply With Quote
Old 03-10-2010, 03:29 PM   #20
Master Electrician
 
Join Date: Mar 2010
Location: Indiana
Posts: 4,413
Rewards Points: 5,082
Default


Quote:
Originally Posted by mopowers View Post
Thanks man. So the difference would only be 0.4% I'm guessing I would never see that in my wallet.

The power used is the same. There is no savings differential!!!!!!!!!!
brric is offline   Reply With Quote
Old 03-10-2010, 03:44 PM   #21
Member
 
Join Date: Jul 2009
Location: Sacramento CA
Posts: 258
Rewards Points: 252
Default


Quote:
Originally Posted by brric View Post
The power used is the same. There is no savings differential!!!!!!!!!!
You're right. Thanks!
mopowers is offline   Reply With Quote
Old 03-10-2010, 05:46 PM   #22
Civil Engineer
 
Join Date: Mar 2009
Location: Boston
Posts: 5,832
Rewards Points: 5,246
Default


There is a small difference in total power consumption due to the greater losses in a circuit running at 120 volts versus 240 volts. The power consumption of the compressor does not change, however some power is consumed in the wiring up to the compressor. The power dissipated by a wire can be computed from the equation P = I * I * R where I is the amperage and R is the resistance of the wire in ohms.

The current I for a 120 volt circuit is twice that for an equivalent power 240 volt circuit. The resistance of the wire is essentially independent of the voltage, but does depend on the size of the wire. Therefore the power loss in a 120 volt circuit is 4 times the power loss of an equal length 240 volt circuit if the wire is sized for the amperage draw at 120 volts. If the wire at 240 volts is sized for 240 volts, you will probably use a smaller wire than the 120 volt case, and the resistance is higher, but the square factor of the amperage typically overcomes the somewhat higher resistance, and you still dissipate more power. Remember, you pay for the power loss in the wiring up to the device.

Example: A compressor designed for 17 amps at 240 volts would require #12 wire, at 34 amps at 120 volts you would use #8 wire. #12 Cu wire has a resistance of 0.159 ohms/100 ft, while #8 wire has a resistance of .063 ohms/100 ft. Assuming a 100 ft run, the losses in the wire are as follows:

120 volts: 34 x 34 x .063 = 73 watts
240 volts: 17 * 17 * .159 = 46 watts

In this case, the 240 volt circuit saves 27 watts of power.
Daniel Holzman is offline   Reply With Quote
Old 03-10-2010, 05:58 PM   #23
Master Electrician
 
Join Date: Mar 2010
Location: Indiana
Posts: 4,413
Rewards Points: 5,082
Default


Quote:
Originally Posted by Daniel Holzman View Post
There is a small difference in total power consumption due to the greater losses in a circuit running at 120 volts versus 240 volts. The power consumption of the compressor does not change, however some power is consumed in the wiring up to the compressor. The power dissipated by a wire can be computed from the equation P = I * I * R where I is the amperage and R is the resistance of the wire in ohms.

The current I for a 120 volt circuit is twice that for an equivalent power 240 volt circuit. The resistance of the wire is essentially independent of the voltage, but does depend on the size of the wire. Therefore the power loss in a 120 volt circuit is 4 times the power loss of an equal length 240 volt circuit if the wire is sized for the amperage draw at 120 volts. If the wire at 240 volts is sized for 240 volts, you will probably use a smaller wire than the 120 volt case, and the resistance is higher, but the square factor of the amperage typically overcomes the somewhat higher resistance, and you still dissipate more power. Remember, you pay for the power loss in the wiring up to the device.

Example: A compressor designed for 17 amps at 240 volts would require #12 wire, at 34 amps at 120 volts you would use #8 wire. #12 Cu wire has a resistance of 0.159 ohms/100 ft, while #8 wire has a resistance of .063 ohms/100 ft. Assuming a 100 ft run, the losses in the wire are as follows:

120 volts: 34 x 34 x .063 = 73 watts
240 volts: 17 * 17 * .159 = 46 watts

In this case, the 240 volt circuit saves 27 watts of power.
You are assuming different sizes of wire which is not what has been discussed here.
brric is offline   Reply With Quote
Old 03-10-2010, 07:08 PM   #24
Electrical Contractor
 
kbsparky's Avatar
 
Join Date: Sep 2008
Location: Delmarva
Posts: 3,368
Rewards Points: 2,000
Default


Quote:
Originally Posted by brric View Post
You are assuming different sizes of wire which is not what has been discussed here.
It is a valid assumption, since the original question postulated using the same compressor wired at different voltages. Even with the larger sized wire for the 120 Volt connection, you still save a few watts wiring it for 240 Volts.

If one were to use the larger conductor wired for 240 Volts, one could argue that more watts could be saved. But the difference would not be worth it.

The rule of thumb on this or any other motor load is always use the highest available voltage when installing such circuits.
__________________
-KB

Life is uncertain -- eat dessert first!!
kbsparky is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
240v Air Compressor to 120v help ruacoltsnut General DIY Discussions 10 11-11-2010 04:05 PM
Pulling 120V outlet from a 240V circuit? npage148 Electrical 12 11-08-2009 11:29 AM
Do you think a tool running at 240v works better than at 120v? Piedmont Electrical 39 07-03-2009 09:50 PM
Understanding 120V branch loads in 100A 240V system WaldenL Electrical 17 02-17-2009 09:15 AM
Cattle waterer 240V - also need 120v! 2wheelinusa Electrical 6 10-05-2008 06:39 PM




Top of Page | View New Posts