Usually the 300W rating is what the load will dissipate.  If the supply
is 75% efficient, the load gets 300W and the supply has to dissipate
100W.

If the load is in the same box as the supply, such as in a PC, and the
supply fan is doing all the cooling, then the fan in the above case
would have to cool the 100W of the supply plus the 300W of the load.

Sherpa Doug

> -----Original Message-----
> From: Micro Eng [mailto:micro_eng@HOTMAIL.COM]
> Sent: Thursday, April 11, 2002 12:56 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE]:BTU's of a system
>
>
> changing topics from my current ICD problems...
>
> If you have a 300W power supply, and *assume* (however bad it
> is) that it
> will be drawing a total of 300W (lets pretend its a perfect
> world and no
> power factor correction, or the supply is PF corrected)then
> if you want to
> calculate the BTU's to determine the cooling requirements, do
> you simply use
> the 300W figure?
>
> What I am getting at can you safely approximate the fact that
> the entire
> 300W will at some point be dissipated as heat?  Or only a certain
> percentage?
>
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