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PSU fan spinning randomly at idle?

  • Thread starter Thread starter Deleted member 205776
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Deleted member 205776

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Recently got a Seasonic Prime PX-750 to replace my "aging" CX 650, and it has been great so far, no issues, no noise, reduced GPU coil whine. Well there is a faint "whistling" noise (not as high pitched) during gaming if I put my ear next to it, but not nearly as annoying as the literal soda acid noises the Ion+ was making.

But sometimes, at idle, I hear the rattle of the FDB fan as it starts and then stops. This is while under 300W (the supposed point where the fan will start spinning, as Seasonic claimed), like 100W system load. If I turn on the fan by turning Hybrid mode off, the air coming out of it is warm. The air coming out of my CX 650 was cold, but that PSU always had its fan on whereas this one doesn't.

It's not annoying and I can't hear it with headphones on, I just wonder why that is. Should I just turn Hybrid mode off and keep the fan always spinning? It's inaudible anyway. But I worry about dust buildup, especially on the fan bearing, even if I have a dust filter on the bottom which I do (I clean out my entire case once a week). I don't usually take PSUs out of my case to clean them -- I just blow some compressed air on it from under my case.
 
The "fan off under 300W" is approximate, and depends on temperature of internal parts, not some integrated kill-a-watt meter that cuts in when it detects 300W.

It's possible a device in your PC is drawing disproportionately high 5V or 3.3V which are very inefficient to convert to and therefore generating a local hotspot in the PSU that mandates the fan.

I wouldn't worry about it, but idle stop is kind of pointless when the PSU fan is quiet once running. It's probably better for the PSU lifespan to maintain a steady temperature than to keep thermal cycling its components by continually triggering the fan on and off.
 
Chrispy_ said:
The "fan off under 300W" is approximate, and depends on temperature of internal parts, not some integrated kill-a-watt meter that cuts in when it detects 300W.

It's possible a device in your PC is drawing disproportionately high 5V or 3.3V which are very inefficient to convert to and therefore generating a local hotspot in the PSU that mandates the fan.

I wouldn't worry about it, but idle stop is kind of pointless when the PSU fan is quiet once running. It's probably better for the PSU lifespan to maintain a steady temperature than to keep thermal cycling its components by continually triggering the fan on and off.
Click to expand...
That makes sense. I think I'll keep the fan on and see how the dust buildup is after a month or so.

Update: Left the PSU fan on since making this post and now the air coming out of the PSU is cold, surface cold to the touch. Glad nothing's overheating in there at idle, that would've been annoying. Fan isn't even audible so I might just leave it on. PC is on my desk, not on the floor.
 
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