Is my Power supply theory correct?

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laststop
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Is my Power supply theory correct?

Post by laststop » Sat May 21, 2016 8:02 pm

OK so we all know how new power supplies all have a hybrid fanless feature where about 25% and below load the fan does not spin. Now say you have a decently power efficient system that at peak load it draws about 280 watts but on average it's lower than that say 225 watts. Obviously current suggestions would be about a 450 watt PSU would be plenty as 225 is its 50% point where it is most efficient and most gaming you are around that mark not the peak.

Now my thought was well what if you just get one of those big awesome 1500 watt 80+ titanium units where it's 25% load number is 375 watts and your peak usage is well below that and average usage of 225 watts is literally only 15% of the unit. The 1500 watt unit has the hybrid fanless operation so would that mean since the PC is unable to get to even 20% of the power supplies max load, even at peak wattage draw, that the power supply will permanently be in fanless operation? Is this a viable strategy to get complete fanless operation without having to get one of those actual fanless PSU's? I know it is not a very economic way to go but if money doesn't matter is this a good strategy?

quest_for_silence
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Re: Is my Power supply theory correct?

Post by quest_for_silence » Sat May 21, 2016 10:32 pm

laststop wrote:if money doesn't matter is this a good strategy?

Is just overbuild/overkill a strategy? And to do what? That's not so clear to me.

laststop
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Re: Is my Power supply theory correct?

Post by laststop » Sat May 21, 2016 10:47 pm

What don't you understand? It's for a silent build. If you want the PSU to NEVER have to turn it's fans on. I don;t want to retype it all. Since PSU's keep their fans off if the load is below 25% if you buy a big enough PSU so even your MAX load is less than 25% then will the PSU fans NEVER have to turn on therefore the PSU is completely silent always. I was asking if that is correct.

I don;t get how you do not understand what I am asking. Ill make it as short and sweet as possible.

If you buy a large enough hybrid semi fanless PSU so that your systems peak wattage always stays 20% or less below your PSU's rated wattage does your PSU stay in fanless mode permanently making the PSU completely silent always?
Last edited by laststop on Sat May 21, 2016 10:50 pm, edited 1 time in total.

Vicotnik
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Re: Is my Power supply theory correct?

Post by Vicotnik » Sat May 21, 2016 10:49 pm

What's the point of a 1.5kW PSU for a sub 300W system? Future proofing? ;) If you want guaranteed fanless operation, why not a passive PSU with a capacity closer to the actual power consumption? It should be both cheaper and more power efficient.

laststop
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Re: Is my Power supply theory correct?

Post by laststop » Sat May 21, 2016 10:51 pm

Vicotnik wrote:What's the point of a 1.5kW PSU for a sub 300W system? Future proofing? ;) If you want guaranteed fanless operation, why not a passive PSU with a capacity closer to the actual power consumption? It should be both cheaper and more power efficient,

it's just a hypothetical question thats all and no that's not the point the point is to buy a large enough PSU that it always stays in fanless mode since 225 watts is only 15% of 1500 watts. The actual fanless PSU's just kinda suck and they run really hot.

The question I am asking is will the hybrid semi fanless PSU's stay in fanless mode permanently if you get a high enough wattage PSU that you are always below 20% of its rated wattage therefore keeping it in fanless mode permanently or will it heat up too much eventually even if it's only 15% of its rated wattage and the fans do still kick on eventually?
Last edited by laststop on Sat May 21, 2016 10:56 pm, edited 2 times in total.

Vicotnik
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Re: Is my Power supply theory correct?

Post by Vicotnik » Sat May 21, 2016 10:52 pm

Hypothetical how? Would it work? Sure. But why?

laststop
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Re: Is my Power supply theory correct?

Post by laststop » Sat May 21, 2016 10:55 pm

Vicotnik wrote:Hypothetical how? Would it work? Sure. But why?
Because those 400-500 watt full fanless PSU's suck. They run incredible hot like 85C constantly and radiate a lot of heat into the case.

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Re: Is my Power supply theory correct?

Post by Vicotnik » Sat May 21, 2016 10:59 pm

The bigger PSU would be less efficient than the smaller one and generate even more heat.

edh
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Re: Is my Power supply theory correct?

Post by edh » Sat May 21, 2016 11:34 pm

laststop wrote:Because those 400-500 watt full fanless PSU's suck. They run incredible hot like 85C constantly and radiate a lot of heat into the case.
No problem here with mine. Do you have personal experience with one?

In fact, if you were to run a 1500 Watt PSU at 200W, it till run less efficiently that a 400W passive PSU, thus radiating MORE heat into the case.

Also, if you generally are using more than 200W your components cooling requirements will be greater than the 500rpm spinning of a decent fan cooled PSU fan at medium load anyway.

Buy a 1500W PSU if you wish, it's your money but I think you're wasting it.

laststop
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Re: Is my Power supply theory correct?

Post by laststop » Sun May 22, 2016 12:09 am

Reading comprehension people. It was a hypothetical question. If you had a hybrid semi fanless 1500 watt PSU and kept the load at 225-250 watts would it's fan stay off permanently. Never once did I say I wanted to buy one. It was a question out of curiosity that is it. Geez

edh
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Re: Is my Power supply theory correct?

Post by edh » Sun May 22, 2016 1:57 am

laststop wrote:Reading comprehension people. It was a hypothetical question. If you had a hybrid semi fanless 1500 watt PSU and kept the load at 225-250 watts would it's fan stay off permanently. Never once did I say I wanted to buy one. It was a question out of curiosity that is it. Geez
Alright, calm down. We know it's just a hypothetical thing, perhaps look at your own reading comprehension and check through everyone else's answers and see where exactly we don't deal with it as a hypothetical question?

Hypothetical or not, it doesn't make sense to use such a PSU.

quest_for_silence
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Re: Is my Power supply theory correct?

Post by quest_for_silence » Sun May 22, 2016 2:09 am

laststop wrote:What don't you understand?
The logic/premises/boundary conditions behind your statements/questions. Sometimes it's not enough to write once to be understood by other people, particularly in a multi-language/multi-cultural community (even if we all use english, any of us with his own, different proficiency).
And being misunderstood by other people doesn't mean other people want/like poking/bashing you, I hope that's crystal clear.

laststop wrote:I don;t want to retype it all.

Me too: I was looking for rephrasing/explaining/argumenting, not a mere retyping.

laststop wrote:I was asking if that is correct.

That's true but it depends of the PSU's primary thermistor (how much hot is really hot for that guy): set aside the MCU-based (aka digital) PSUs (which can be programmed), all analog PSUs use temperature, not power draw, to start the fan.

laststop wrote:If you buy a large enough hybrid semi fanless PSU so that your systems peak wattage always stays 20% or less below your PSU's rated wattage does your PSU stay in fanless mode permanently making the PSU completely silent always?

Yes and no: since 2009 the best PSUs (the best for the silence crowd) do not need to have 1500W rating to supply (to say) 2-300W of fanless operation, which is enough for the vast majority of rigs. Some of them are cool enough to supply 4-500W of fanless range.
On the other hand you may want the largest AXi just in case you were running a largely inefficient contemporary Crossfire setup, but then noise-wise your problem will not be the PSU.

laststop wrote:
Vicotnik wrote:Hypothetical how? Would it work? Sure. But why?
Because those 400-500 watt full fanless PSU's suck. They run incredible hot like 85C constantly and radiate a lot of heat into the case.
I guess it will be similar with reference to larger PSUs: mainly because it is not the rated wattage, but mostly the lack of active cooling to heating the internals (and obviously the relevant efficiency plays some role too).

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