Help! No sign of life

[Smart_Guy]

Electricity is cheap here. But at least right now my SLI setup requires a 750w PSU (with the system). The overclocked CPU uses maybe 100w more. The remaining stuff; 4 fans, SSD and 5 HDD's use a little of the remaining of the 1000w. Maybe a 850w PSU was a better choice? But anyway, the reason I got this one is to keep it for ages to come and to run anything I throw at.

It's weird tho. Let's say only 500w is being used, where does the remaining (minus the efficiency loss) go if the PSU pulls the complete 1000w it's rated for out of the wall? I know energy is never lost but changes from one form to another. Running the fan and producing heat maybe? The fan is small and quiet to draw that much and so little is the heat.

 

[AMD_man]

I never tested this, but I doubt PSUs pull the maximum power from the wall all the time. The remaining current would have to be run through a random resistance to produce heat or something. That would make efficiency ratings pointless, since no matter what you are already wasting a lot.

 

[Smart_Guy]

Yes, that's what I know too. The only loss I know of besides the efficiency loss is the extra price for bigger PSU's and not using the extra power it can give. As for the remaining current, that would be 150w / 12v = 12.5 amps, and that's if everything else is working at full load. At idle, it could be +600w / 12v = +50amp. How much heat can that cause now!

 

[Celery]

The wasted energy will be heat. And what does the 80% (Gold or Platinum or whatever) mean?

Anyone? Anyone? (from Ferris Bueller)

 

[AMD_man]

The wasted energy will be heat. And what does the 80% (Gold or Platinum or whatever) mean?

Anyone? Anyone? (from Ferris Bueller)

Yeah it'll be heat but we were saying that it doesn't pull the entire 1000W if you can't use them. It doesn't have a conductor to just dispose of current. Like a short but not really because it would have a resistance.

The 80+ is the efficiency. If it's bronze it's 82% I think, if it's gold it's 87 or more (I don't really remember). So if the PSU is rated Gold, let's say it has 87% efficiency, so it will actually be pulling (1000/0.87)W from the wall to provide 1000W to the computer (when at maximum load). So the remaining 150W would be what it's being dissipated as heat (because of the Joule effect).

 

[Celery]

I have a confusion here and my memory's not serving me right. Back to research and it's true that it draws what it's needed but there's something about the PSU being too big for the system and the wasted wattage as heat.

I think it's the old school thinking that's getting in the way. The PSUs are more efficient than before.

 

[AMD_man]

I have a confusion here and my memory's not serving me right. Back to research and it's true that it draws what it's needed but there's something about the PSU being too big for the system and the wasted wattage as heat.

I think it's the old school thinking that's getting in the way. The PSUs are more efficient than before.

PSUs reach maximum efficiency when they are at 50% load. Maybe that's what you are thinking of?

 

[Celery]

No, I think the PSUs used to have transformers and now mostly solid state.

 

[Cortb]

So if the PSU is rated Gold, let's say it has 87% efficiency, so it will actually be pulling (1000/0.87)W from the wall to provide 1000W to the computer (when at maximum load).

If it's 87% efficient it would be putting out 870w to the computer when it takes 1000w from the wall right? to put out 1000w it'd need to pull 1150w from the wall, if my math is right.

 

[AMD_man]

If it's 87% efficient it would be putting out 870w to the computer when it takes 1000w from the wall right? to put out 1000w it'd need to pull 1150w from the wall, if my math is right.

Yes, the math is right. 1000/0.87 is 1150. That's why I said it would be wasting 150W.