Newb PS Voltage Question

[Techx]

have plans for a mod, and I have a 100W PS.. just say i want to hook up 4 fanbus's that run at 12V each, how many volts will I have left over for additional devices? I read practically the whole faq and still couldn't figure it out.. I know W=Volt*Amp but I have no idea what the amps are?

 

[Elledan]

If this is a PSU which only delivers 12 V, then it should be able to deliver about 8 A. A fan uses around 0.5 A (about 1 A when spinning up), so with four fans connected you should be able to safely use 4 A, 6 A if you're feeling lucky.

 

[Ice Czar]

If this is a PSU which only delivers 12 V.

^

100 watts divided by 12volts equals 8.3 amps
at the temperature the supply was rated (which is likely unknown)
dropping that to 6A is a good idea since it was probably rated at 25C
and you might be as high as 40 > 50C depending in where its located in the case
(like above the CPU Heatsink)

if the PSU puts out all the rails (+3.3V, +5V, +12V) as opposed to being a dedicated +12V supply
(does it have a 20 pin connector? is it an ATX or AT supply? )
either it will have a sticker in the side stating the amps available on each rail or you'll need to reseach that