PSU temperatures
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Posted by GT on August 19, 2008, 9:17 am
Please log in for more thread options Would a 650W PSU run hotter when powering a 484W computer than when powering a 232W setup? Obviously case temperatures would affect things, but if we could isolate that... Does a PSU run hotter when under more load or is its heat output independent of the amount of power drawn from it? | |||||||||||||||||||||||||||||||||||||
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Posted by Mike Walsh on August 19, 2008, 10:28 am
Please log in for more thread options The heat from a power supply will increase as the load increases. GT wrote: -- Mike Walsh | |||||||||||||||||||||||||||||||||||||
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Posted by VanguardLH on August 20, 2008, 2:16 am
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GT wrote: > Would a 650W PSU run hotter when powering a 484W computer than when powering
> a 232W setup? Obviously case temperatures would affect things, but if we > could isolate that... > > Does a PSU run hotter when under more load or is its heat output independent > of the amount of power drawn from it? You cannot consume more power without generating more heat. More power means more heat. 1000 Watts = 0.948 BTU | |||||||||||||||||||||||||||||||||||||
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Posted by ~misfit~ on August 22, 2008, 3:27 am
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Somewhere on teh intarweb "VanguardLH" typed: > GT wrote:
> >> Would a 650W PSU run hotter when powering a 484W computer than when
>> powering a 232W setup? Obviously case temperatures would affect >> things, but if we could isolate that... >> >> Does a PSU run hotter when under more load or is its heat output >> independent of the amount of power drawn from it? >
> You cannot consume more power without generating more heat. More > power means more heat. > > 1000 Watts = 0.948 BTU Indeed. However, the PSU doesn't 'consume' the power, it supplies (most of) it to other devices which consume it. The question was really about PSU efficiency at different loads. The answer (near enough) is that a certain amount of the output is lost as heat in the switching process. A good PSU is rated at 80+ efficiency meaning that, if it's putting 80W out it's using less than 100W with the difference being lost as heat from the PSU. Therefore, assuming that efficiency is linear (it's not but it's often close) a 650W 80% effecient PSU would produce 121W of heat producing the first load mentioned, 484W, and 58W of heat when delivering the power for the 232W 'setup'. Good link: "Everything You Need to Know About Power Supplies" http://www.hardwaresecrets.com/article/181/1 Cheers, -- Shaun. DISCLAIMER: If you find a posting or message from me offensive, inappropriate, or disruptive, please ignore it. If you don't know how to ignore a posting, complain to me and I will be only too happy to demonstrate... ;-) | |||||||||||||||||||||||||||||||||||||
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Posted by VanguardLH on August 23, 2008, 2:15 pm
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~misfit~ wrote: > Somewhere on teh intarweb "VanguardLH" typed:
>> GT wrote:
>> >>> Would a 650W PSU run hotter when powering a 484W computer than when
>>> powering a 232W setup? Obviously case temperatures would affect >>> things, but if we could isolate that... >>> >>> Does a PSU run hotter when under more load or is its heat output >>> independent of the amount of power drawn from it? >>
>> You cannot consume more power without generating more heat. More >> power means more heat. >> >> 1000 Watts = 0.948 BTU >
> Indeed. However, the PSU doesn't 'consume' the power, it supplies (most of) > it to other devices which consume it. > > The question was really about PSU efficiency at different loads. True, but since efficiency is never 100% then the more power consumed by the target devices (mobo, memory, cards, drives, etc.) means the more power also consumed by the PSU. For a 600W PSU, if efficiency were 70% (a measure in difference between input and output power at some load), a load of 300W means the PSU is consuming 75W (300/.8 - 300, or 375W input power minus the 300W load). For a 400W load, the PSU eats 100W ( 400W/.8 - 400W, or 500W input power minus the 400W load). As the PSU consumes more power under a higher load, the more heat is produced by the PSU itself. Of course, assuming 80% efficiency is being generous since, as you said, that's typical of "good" power supplies. So back to the OP's question of will a PSU run hotter with a 484W load than with a 232W load, and whether efficiency were 70% or 80% for the PSU, my answer still applies. More power consumed means more heat. No matter what PSU the OP uses and irrelevant of the PSU's maximum capacity (i.e., max load), you cannot *consume* more power without generating more heat because. Efficiency is never 100% for the PSU. | |||||||||||||||||||||||||||||||||||||
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> Would a 650W PSU run hotter when powering a 484W computer than when powering
> a 232W setup? Obviously case temperatures would affect things, but if we
> could isolate that...
>
> Does a PSU run hotter when under more load or is its heat output independent
> of the amount of power drawn from it?