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Tzale
Proud Libertarian Conservative
Premium
join:2004-01-06
NYC Metro

120v Vs. 240v Power Input

I'm not an electrical engineer, and only know the basics of electricity... I was thinking today that since my power supply can accept 120v and 240v, why not use 240v due to the increased efficiency? I believe higher voltage devices are more efficient due to less heat loss, and I have a spare 240v outlet available next to my computer that is not used. Would this be worth it at all? Even if it only saves a few bucks a year?

-Tzale
--
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
-:-
"I believe the very heart and soul of conservatism is libertarianism."~Ronald Reagan
-:-
www.freestateproject.org - LIVE LIBERTY


fiosuerny

@verizon.net
My guess is that the wattage used, and thus the kw/h you pay for, will be nearly identical on 110v or 240v.

But if you are really curious, buy a Kill A Watt meter and put it between each wall outlet and your power supply for a day or 3. The meter will answer your question.


aurgathor

join:2002-12-01
Lynnwood, WA
kudos:1
reply to Tzale
In that case, the difference in efficiency will be minuscule, at best.
--
And the winner is:


Jahntassa
What, I can have feathers
Premium
join:2006-04-14
Conway, SC
kudos:4

1 edit

1 recommendation

reply to Tzale
I may be stupid (it's been said before), but I was under the impression that a computer power supply expecting 240v is still expecting a Hot / Neutral / Ground 3-pin setup. If you don't have a single-leg 240 hot in that outlet, i'm not sure if it would work.

Again, I could be wrong, but I believe you'd need something like an L6-20 240v 4-pin outlet combined with a PDU (Power Distribution Unit) that converts the 2-leg 240v to one.

I would be wrong about the L6 and all of that. In all honesty i'm not sure if PSUs can take a Hot/Hot/Ground in 240v or if it has to be Hot/Neutral/Ground.

Most PSUs will have either a switch, or be autoswitching, as far as the voltage goes. I'm just not certain how to wire it up in a standard residence.

Still, I don't believe it would make things really any more efficient or less costly in terms of power bills.


Dogwood
Premium
join:2001-01-14
Texas
reply to Tzale
It's like Jahntassa says, the purpose of the 240V switch is for European use.
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Proud Member of Team Discovery

moes

join:2009-11-15
Cedar City, UT
Our 120v power supplies do not like 240v at all. I know it might sound efficient but trust me on this one thing, They make nasty smoke and fireworks when given to much juice xD


Subaru
1-3-2-4
Premium
join:2001-05-31
Greenwich, CT
kudos:1
reply to Tzale
what happens when you flip it to 240V with it plugged into a 120V outlet?

Kiwi
Premium
join:2003-05-26
USA/MidWest
kudos:1
said by Subaru:

what happens when you flip it to 240V with it plugged into a 120V outlet?
*Poof*


Subaru
1-3-2-4
Premium
join:2001-05-31
Greenwich, CT
kudos:1
ah that's what I thought I wonder how many people that's happen to


Freddy
Premium
join:2005-05-17
Arlington, VA
kudos:2
reply to Tzale
All,

With a system I built once, the case came with the little power supply switch set to 220/240v. I didn't notice this because I never found it necessary to check. The switch had always been pre-set to 110/120v.

After putting everything together, I powered it up. It started to boot, but shut down when I tried to enter BIOS to set the boot order to the CD-ROM drive to install Windows.

I tried it again and the same thing happened. I checked everything I could think of, but I found nothing wrong. I spend some time troubleshooting, but the computer always shut down during the initial boot process. I was stumped!

To make a long story short, while poking around in the rear of the computer, I finally noticed by accident the switch set to 220/240v. I flicked to over to the 110/120v setting. I really wasn't looking for that setting.

Bingo! After setting the switch to its proper setting, the computer booted to the Windows installation CD and has been running properly since.

I guess I can say that nothing terrible happened when I tried running the computer with the switch set to 220/240v. It just wouldn't work.

Freddy


Kilroy
Premium,MVM
join:2002-11-21
Saint Paul, MN
reply to Subaru
Actually it just doesn't work. If you plugged it into a 240v when set to 120v you might let the smoke out. As you know, all electronics run on smoke and when it leaks out they stop working.

It used to be a good practical joke to switch someone's PSU to 240v.
--
When will the people realize that with DRM they aren't purchasing anything?


peter_m
Premium
join:2005-07-13
Canada, QC
said by Kilroy:

It used to be a good practical joke to switch someone's PSU to 240v.
Tell that to bored high school students!

GunnarDanne

join:2002-12-02
Crown City, OH
reply to Freddy
I did the same thing back in 2005.


DKS
Damn Kidney Stones
Premium,ExMod 2002
join:2001-03-22
Owen Sound, ON
kudos:2
reply to Tzale
said by Tzale:

I'm not an electrical engineer, and only know the basics of electricity... I was thinking today that since my power supply can accept 120v and 240v, why not use 240v due to the increased efficiency? I believe higher voltage devices are more efficient due to less heat loss, and I have a spare 240v outlet available next to my computer that is not used. Would this be worth it at all? Even if it only saves a few bucks a year?

-Tzale
Where power systems are 240 volt, they are 50 HZ. In North America 120v power is 60HZ. Huge difference. And there can be variance in 120v power. It can be as low as 100v and as high as 130v.
--
Need-based health care not greed-based health care.


Subaru
1-3-2-4
Premium
join:2001-05-31
Greenwich, CT
kudos:1
I forgot all about 50Hz


heat84
Bit Torrent Apologist

join:2004-03-11
Fort Lauderdale, FL
reply to Subaru
said by Subaru:

what happens when you flip it to 240V with it plugged into a 120V outlet?
What happens if you do the opposite in Europe? It really will "*Poof*" right?


Subaru
1-3-2-4
Premium
join:2001-05-31
Greenwich, CT
kudos:1
haha good question

you know now thinking about it why can't they do like most electronic products now by one plug can work in all places without having to flip a switch?


Dream Killer
Graveyard Shift
Premium
join:2002-08-09
Forest Hills, NY
kudos:1
active pfc and all laptop chargers do that now. you just need to physically change the type of plug it is.


Subaru
1-3-2-4
Premium
join:2001-05-31
Greenwich, CT
kudos:1
only reason why I never got a active pfc PS is because I need to buy a $400+ UPS if I want to run power backup on it.

keno5net

join:2002-01-05
Milwaukee, WI
reply to Tzale
Most computer power supplies you find today don't even have a switch for selecting 120/240 they work on all voltages from around 85vac to nearly 300vac. The first thing that happens to the ac is it goes into a rectifier and becomes dc which is switched at high frequency the resulting pulses are controlled to let just enough of the power through to power the computer

This is an over simplified description.

The point being that neither the voltage or frequency will severely affect the operation of the Power supply. The efficiency does improve at higher voltages but the difference is not huge. Most likely the effort to supply 240v to the system isn't worth the savings.

Here is a nice article on how these power supplies work. A much better explanation than my crude attempt above.

»www.hardwaresecrets.com/article/327