Question Is oversizing the psu a way to reduce noise and heat?

[Slapstick83]

I'm building a brand new pc and I'm considering psu. The system is a ryzen 2700x / RTX 2080TI build, with not much else. I've currently opted for the Corsair HX750i psu: https://pcpartpicker.com/user/Slapstick83/saved/r9L8YJ

I'm quite obsessed with eliminating noise, although I'm obviously also going for a performance build. I'm wondering if there would be a benefit to going even higher on the wattage for the PSU? Would a 1000W+ PSU generate less heat and fan noise due to the power draw being below the 50% utilization mark? My concern is at this point neither my electricity bill nor price - merely heat and noise.

Any other comments on the build is of course welcome (and I'm going for the Ryzen in anticipation for Zen2)

Best regard,

 

[Dunlop0078]

Maybe in terms of noise, the 1000watt HX likely wouldn't even turn on it's fan unless the system is under heavy load, even the 750watt version to a lesser extent. Two power supply's with the same efficiency rating will effectively produce the same volume of heat regardless of it's rated wattage in my understanding. The load on the power supply and it's efficiency at that load determines how much heat it will produce, again from my understanding.

 

[tennis2]

^This. While modern PSUs' efficiency curves are relatively flat (most good reviews will give an efficiency curve), they still peak at around 50% duty cycle. So that point is going to be your optimal Power vs. Heat.

The only thing you can hope for is semi passive fan operation. If you decide to spend excessively in that regard, make sure you read reviews or product specs to determine at what load the fan starts spinning. Different platforms start the fan at different times. Also, since I'm usually shopping in the 550-750W range, I'm not sure how semi passive fan operation works in say, 1200W PSUs. The housing of the PSU is generally slightly larger, but a 550W PSU passive under 45% load is 250W, whereas a 1200W PSU @ 45% is 540W. That's a LOT of power/heat to dissipate passively in a [relatively] small enclosure with limited heatsink area. Not sure it's even possible. It may be that the actual wattage determines the passive point, so a 1200W PSU may only be passive at 20% load, whereas, that 550W PSU is passive at 45%. Both at the same wattage. Get my drift?
I would expect that 1200W PSUs are better equipped to cool higher wattage, so the higher wattage PSU may win in the passive wattage. Also, the fan may not have to spin as fast at your expected load. But that is all entirely dependent on the fan on the PSU and the PSU quality. It's entirely possible for a 750W PSU to be quieter at the same load as a 1200W one. Again, read reviews. Jonnyguru is a good site.

 

[Slapstick83]

Thanks for the good feedback
Looking at the tests of the HX1200 version it seems like the fan is idle until 500-600W draw. Which may actually be more than my rig will consume! If this means I’ll have a cool and passive psu this could be very interesting

However, whatever heat produced would then rise into the case. Maybe it would be better with a psu which will actually have a fan running at near-silent levels so it doesn’t heat the case. I’m already concerned that 3 case fans isn’t enough to cool the cpu and RTX2080ti without them getting warm enough to get rather audible

 

[InvalidError]

Where a larger PSU may be beneficial for quieter operation is simply from being in a larger enclosure to accommodate the extra components and larger heatsinks, which decreases power density in the PSU and improves heat transfer to air. Take a 550W PSU, put it in an over-sized ATX PSU case with PCB and heatsinks to match and you'd get similar results to just super-sizing to a 1600W PSU as far as a 400W system is concerned.

 

[tennis2]

Most PSUs with semi passive fans have a toggle button to disable that feature and have the fan spinning all the time. I have a EVGA G2 and a Seasonic XP2 which both have such switches. If the load is below the typical semi passive cutoff, I can't imagine the fan would spin very fast.