HX750 - fan noise at idle

[broadside]

Hi all,

 

I recently replaced an ageing HX650W with a brand new HX750 (80+ Platinum). The former made next to no noise at idle but the latter has a constant loud fan.

 

From what I've read it's supposed to kick in at 40% load which it feels like I shouldn't be hitting, especially since the old PSU was silent. Hopefully you can see my specs attached - I know the R9 390 is an old power-hungry card but is this normal? I've double-checked everything is wired up correctly.

 

Thanks :sunglasse

[Corsair Notepad]

The fan kicks on at specified load and/or temps. Even at idle if you have a lot of RGB you can be drawing enough on the 5v to cause the fan to have to spin up momentarily to keep those components cool enough even at idle.

[jastech]

If he has RGB it'll be about 1.3-4.4w at 5vdc, and that's for a RGB Fogger. He could actually run all his RGB of a few batteries, that's how little they draw. That isn't enough of a draw to heat up a 750w PSU to make the fan spin up on high. At 40% load which would be 300 watts. His R9 390 draws 275 watts maximum, so that would be extreme gaming to require that load.

 

Broadside, may I ask your build? PC that is, Lol

[LeDoyen]

that post is one year old ^^'

and it's very common for RGB to trigger the fan when you start to deck the case with lighting. the power draw you give can be reached by 2 fans. on my setup i've seen power draws in excess of 60 watts on the 5V rail, and it doesn't have a ton of RGB compared to some.

that's enough to warm up the 5V rail electronics and trigger the fan in some cases, like when the PSU is installed with the fan down, even if the main 12V rail is not doing anything.

All the USB peripherals, RGB keyboard and mouse, wired headset and whatever will add to the 5V power draw. it's easy to get that fan spinning.

[jastech]

I know it's an old post, but, others will search and read then learn. Still to hit 300 watts for the 40% load? Try a watt meter at the outlet, betcha it's not even close. Most if not 90% of the PSU calculators are way off, it's a sells gimmick for consumers to buy more wattage when it's not needed. Also the difference in quality inside the PSU makes a major difference. I have thousands of dollars in meters and a $6,000 soldering station. You stated "it's very common for RGB to trigger the fan when you start to deck the case with lighting", Not L.E.D.'s on a PC case, not enough load to do it, if it does then you have a poorly designed and built PSU. A 40% load is needed according to the manual as OP stated. Most the time Seasonic PSU fan wont even spin unless pushed with gaming. Run all the RGB in your case, it'll just sit there. Corsair's is made by Seasonic and Channel Well, but the components Corsair chooses and the soldering job on AX1200i capacitors has failed many units. JMHO

[LeDoyen]

yet it's common.. PSUs installed fan faced down will have the 5V rail sit in its own heat, causing occasional startups of the fan. this behaviour is all over the forum. It's not a power draw issue, just the thermal protection starting the fan. The fan is not only power draw bound.

Everytime that happens, Jonyguru (head of PSU dev) always recommends flipping the PSU over and the fan never kicks in then.

There is definitely enough load with LEDs to do that, if the conditions are met (PSU upside down, no airflow, lots of lighting).

[zultan]

I have an RM850i.  I'm very glad to have the chance to choose between 0 rpm mode and fan mode

so I can keep my fan on, 40%, and my psu is always fresh.

the psu is face down mounted but the case has a filtered air intake on the bottom so the psu brings in fresh air

from the ground.   as you see temps are perfect.

even when gaming or video editing the psu never get "hot" it just warms up a little.

I have quite a lot of stuff connected to the psu, 3 mechanical drives, 4 ssd, 4 rgb 120mm fans, an H150i pro, 1 front rehobus, 

keyboard, mouse, mousepad,   1 usb external hub,   but I never see the fan start if I set it on 0 rpm mode.

anyway I wonder why people say that the fan is "noisy".  at 40% is mostly inudible.

you can hear it mostly when it's working at 100% (in that case maybe you psu is catching fire 😄?)

[LeDoyen]

just for funsies i created a black, and a white profile for RGB. My build has 10 fans (9 LED each), 4 strips with 21 LED each, and two other strips in the reservoir (EK FLT360) and the case (the colored band on the O11XL).

RGB OFF the 5V sits at 9.9W

with all the RGB ON 43.7 W (almost 7A just for shiny lights)

On the usual amber flame effect i use daily which is very tame, it still sits at around 24W

So yep.. it can get the 5V regulator a little warm. just the lighting can take up to 1/4 of the PSU power rating for me (25A)

Edited January 20, 2022 by LeDoyen