PWM fans RPM

Casterina · 30 Jun 2016 at 14:12

doyll said:
That is kinda like asking, "Can I drink of these containers full of water?" We have no idea what the power requirements of the 3 fans are, therefor cannot give you an accurate answer. Motherboard fan headers are usually rated up to 1a / 12a load. Fans use much more power at startup than when running, so I would not load a fan header with more than about 0.7a / 8w of load. If your 3x fans have a combined total wattage of below 8w then yes you can run all three from motherboard fan header.

The Akasa Apache are 0.33A current rating so I'd need to use a PWM splitter which gets power from PSU.

Also, the Apache fan speed is between 600-1300RPM, can it go lower than 600RPM?

doyll · 30 Jun 2016 at 15:06

0.33A sounds like more than I would have guess for a 120mm 1300rpm fan. If that is accurate then I would definitely get a PWM splitter with PSU power.

600-1300rpm may mean it will not idle below 600rpm, I don't know. But some fan do idle lower than their specs say they will. Realistically the Apache is probably very quiet at 600rpm so probably not a problem anyway.

Many of mine will idle a few hundred below specified idle, but not all will. All depends on the PWM% to rpm program on the fan's PWM PCB and how low your motherboard PWM% goes.

Casterina · 20 Jul 2016 at 14:40

Is it bad to control my PWM fans using DC mode? As when using PWM mode, 20% fan speed (lowest I could go) runs at around 900RPM but when using DC mode, it runs at around 300RPM during idle.

So what should I do? Use DC mode or get different fans?

Tealc · 20 Jul 2016 at 20:14

doyll said:
0.33A sounds like more than I would have guess for a 120mm 1300rpm fan. If that is accurate then I would definitely get a PWM splitter with PSU power.

It isn't accurate.

I don't recall the exact current of an Apache but most of my fans operated around the 0.1A-0.2A zone and the Apache was no different.

0.33A may be an inrush current thing which for most purposes can be ignored.