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# Calculate total amps of my power supply multiple rails

Hi.

I know there is a lot of threads regarding this but I wanted to get confirmation.

Most people say that you divide the total watts over 12v and that gives max amps. So eg. dual 12v rails at 450w will give 450 / 12 to give a max output of 37.5 amps.

Now I have a Thermaltake w0311A 430W power supply http://www.thermaltake.com.au/products-model.aspx?id=C_00001773.

Looking at the design it is outputing 350W on the following rails:
+12V1 at 20A
+12V2 at 20A
-12V at 0.3A
+5VSB at 2A

Now how do you calculate the max amps on the 12v is this still 350 / 12 = 29.17A.

The power supply also states total combined +12v output load not to exceed 23A, does this still apply if you are not using the power supply the traditional way .ie. to a computer? If you are simply using the +12v to power a circuit?

Also can someone explain the -12v and how would this factor into calculation?

Sorry if this a noob question or has already been answered however I could not find an exact answer.

Thank you.
Quote:
Originally Posted by psup

Now how do you calculate the max amps on the 12v is this still 350 / 12 = 29.17A.

The power supply also states total combined +12v output load not to exceed 23A,

Also can someone explain the -12v and how would this factor into calculation?

20 amps at 12 v = 120 watts (volts x amps = watts)

That PSU will not put out more that 23 amps on the COMBINED 12 v rails.

23 amps at 12v = 276 watts

The -12v rail is still power the PSU has to put out. It's just the opposite polarity.

It doesn't make any difference what you connect it to, at slightly over 276 watts (being a cheepo thermaltake) it will burst into flames, burn your house down and make you the laughingstock of the neighborhood, to say nothing about how this will reflect on your mother.
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 My System (15 items)
CPUMotherboardGraphicsRAM
FX6300 Black M5A99X EVO R2.0 Nvidia GTS450 Team Vulcan PC3 12800
Hard DriveOptical DriveCoolingOS
Samsung 840 PRO Asus DRW-1608P (x2) Custom Water Cooling Win7 (Ult), Win 8.1 & Win Server 2012 R2
MonitorKeyboardPowerCase
2 X Samsung 915N Ducky Shine III, Blue Cherry/Blue LEDs PCP&C 1kw Lian Li PC-71 (W/Window)
MouseAudio
Logiteck G400s none
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