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 Krazy Owl Aug 15, 2012 12:39 PM

PSU power consumption question

I would like to know if a 430W psu for exemple with a power draw of 120VAC 10A (1200W) will always draw the 1200W or it will work at lower than that and adjust upon demand on the AC side?

If you got a 500w psu with 80% efficiency will it mean as exemple 120v 10A 1200W power draw all the time but with up to 500W on the DC side adjusting on demand?

Thank you ! :)

 Frick Aug 15, 2012 01:01 PM

It will use what it use. I'm not sure I understand what you mean.

 Krazy Owl Aug 15, 2012 01:04 PM

Look on side of a psu. Incoming AC current Volt 120V with Amperage = total AC current withdrawn. But Let's say your 500W psu draw only 300w from computer will it still need the same AC current input or it's auto adjusting also like the Dc side of the psu that power the computer?

 JrRacinFan Aug 15, 2012 01:05 PM

It adjusts as needed on both sides.

 TheLaughingMan Aug 15, 2012 01:08 PM

Its like this: A 500 W PSU will, at max, output 500 W. It will as JR said, adjust to the demands of whatever it is powering on the intake side as it will only draw what is needed up to 500 watts. If it is 80% effecient this means to give that 500 W it will be drawing 625 watts (120 VAC x 5.208 amps).

 Krazy Owl Aug 15, 2012 01:09 PM

Ok thank you! I would like to use a 1000W Dell psu someone gave me and use it to power up the computer and other 12v stuff like light bulbs and fans for my bedroom. Didn't want it to draw a shit load of current to light a single DEL bulb :P

 Krazy Owl Aug 15, 2012 01:12 PM

Quote:
 Originally Posted by TheLaughingMan (Post 2698308) Its like this: A 500 W PSU will, at max, output 500 W. It will as JR said, adjust to the demands of whatever it is powering on the intake side as it will only draw what is needed up to 500 watts. If it is 80% effecient this means to give that 500 W it will be drawing 625 watts (120 VAC x 5.208 amps).
So my 430W psu draws at max load 120V and 10amps = 1200W

430/1200 X 100 = 36% efficiency! That blows! lol

 Frick Aug 15, 2012 01:45 PM

Quote:
 Originally Posted by Krazy Owl (Post 2698312) So my 430W psu draws at max load 120V and 10amps = 1200W 430/1200 X 100 = 36% efficiency! That blows! lol
Er no. 120V 10A is the input, not output. And it does not have a 120V line. :)

 ChristTheGreat Aug 15, 2012 02:01 PM

A 500w PSU, will will use a maximum of 500w (normally) inside the computer. like TheLaughingMan said, if it has a effiency of 80% it will draw 625w at the Wall, because of the Joule Effect. When electricity go into the power supply, there will be heat, and you will loose a bit of power. so if you draw 625 from the wall, you PSU will delivrer 500w inside the computer, if that PSU has an effiency of 80% (Which means there is a lost of 20% from the joule effect)

Big example, if you plug your christmas tree, you won't take 1200w, it will take what it needs. I'm not really sure of your question, but I hope this answer. If you don't use all the power available, your PSU won't use it, it will use what it need, and what he is able to use.

 Krazy Owl Aug 20, 2012 10:52 PM

Ok it all answer my questions. So I'll figure out how to go on with my 12V setup project. I know for sure I could cut some 12V wires on it and put on a car lighter adapter to charge many things at same time like cell phone, portable dvd player, etc.

 LGV Aug 20, 2012 11:27 PM

get something like thet
http://www.powermeterstore.com/p4578...ategory_banner

In case you got 430 watt PSU

a, If PC need idle, lets assume 150 watt usage, then your PSU may pull 215 or more from wall.
b, you play on PC , lets say PC need 300 watt , then your PSU will draw from wall 430 watt
( bad brand may write 430watt the max your PSU can draw FROM WALL)

2, if good make
a, If PC need idle, lets assume 150 watt usage , then your PSU may pull 200watt or more from wall.
b, you play on PC , lets say PC need 300 watt , then your PSU will draw from wall 360 watt
( god make usually write what the PSU CAN deliver to your PC )

This is just example

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