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Running DC mode on PWM Fans better?

conanti
By conanti
in Cooling
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Posted

TLDR: Is running DC voltage on PWM capable fans a more optimal power delivery mode and more consistent?

 

Hi all,

 

Hope everybody is coping and keeping safe with the blight that is Covid.

 

Fans in question: 6x Corsair ML Pro RGB all hooked up to the Corsair Commander Pro.

 

I was mucking around with my fan profiles today as I am trying to optimise my fan performance on my radiators (EK 360ml PE). If my fans go below 800 rpm I start to get a much hotter build and the fans make a bit of a clicking noise. I assume this is due to the motor spinning too slowly as soon as I hit around 750rpm or higher it goes away. Conversely going up to 1600 RPM nets me about a 10 degree drop at the cost of my room sounding like a busy airstrip. I tried setting up my fan curves but no matter what I do with spin up/down time or even having it go from 800-900-1000 rpm nets me a very annoying motor wine issue and I can't stand it constantly speeding up and slowing down I prefer a set RPM. My solution is very simple I just bought another 6 corsair ML pro fans to run in a push/pull set up with the idea of setting them all at 50% (850 rpm) which is basically inaudible. 

 

Now the question:

 

I know that if you buy a DC fan it can't utilise PWM and hence will be stuck running at full-speed or full voltage. As my fans are PWM they can be used in PWM or DC mode. Now from my understanding PWM pulses the full voltage at different intervals to achieve the desired speed which I assume could be causing me some of the whine issues and inconsistent RPM speeds 780-820. Where as DC voltage is constant but just lowered to meet the the desired speed. I noticed on a DC voltage my fans run about 50 rpm higher (850) but seem way more consistent at 850 rpm - 3rpm variance. 

 

So if I set my fans at a flat 50% and don't have them spin up or down wouldn't it be better to use DC mode instead of PWM? I know using either won't damage my fans. I also don't care about saving energy as it's such a small component in relation to the full build the power savings would be miniscule.

 

Really looking to learn and expand my knowledge beyond the forums I have already read on the topic. Really want to understand exactly how it works and if there is a definitive answer. If PWM is a superior power delivery i'll just set at 50%. Thanks in advance!

 

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Posted

ML Pro's require 12v for the magnetic bearing to levitate so use pwm.

If you ever need help with a build, read the following before posting: http://linustechtips.com/main/topic/3061-build-plan-thread-recommendations-please-read-before-posting/
Also, make sure to quote a post or tag a member when replying or else they won't get a notification that you replied to them.

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Posted

The ticking noise seems odd. Those fans are rated to run even lower speeds, 400-1600rpm. So if they make noise at 400rpm, then there's some issue with them.

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