PWM Vs DC - Case fans

Fernanjoe · 10 Jul 2016 at 16:48

Hello Peoples,

So i have just re-built my pc after getting a new case and im looking for some advice on keeping the system as quiet as possible. I stuck in the old case fans from my previous case - Enthoo Pro Mid Tower Case - so im using the 200mm one at the front and a 140mm as an exhaust.

They are both 3 pin fans and i think are only capable of being either on or off? if i set them to DC in the bios they just stop - is that because the temps in the case arent high enough to get them to kick in? and is there any danger in leaving them off?

I have the cpu watercooled and so there are 2 fans pushing air through the rad, so some air in the case is being shifted out.

So really im asking if having the fans on DC, meaning that they are off most the time is a bad thing or should i invest in some 4 pin fans that i can set to be on low? Cheers for any help.

doyll · 10 Jul 2016 at 17:45

Those 3-pin fans use variable voltage speed control. The 200mm is not much good.
What case do you now have? I have no idea why they stop when switched to DC in bios. Could be any of a number of things causing this for not enough voltage to, well. whatever.

Can't really say if it's a bad thing because there are too many unknowns. Let us know what all you have from case to fans, motherboard, and how everything is hooked up.

Fernanjoe · 10 Jul 2016 at 18:09

Cheers man.

The new case is a Thermaltake core x5 (i know, its huge). Mobo is an asus sabre z97 mark 1. I have the two WC rad fans plugged into the cpu and cpu_opt. The front 200mm (that i took out of the ethoo pro) is plugged into cha_fan1 and the 140mm exhust (again taken out of the ethoo pro) is plugged into Cha-fan2.

Im not sure what type of fans they are other than Phantek case fans, 3pins.

Ive been googling a bit and i think i either need to get some 4 pin fans (so i can just have them running at a very low rpm) or some sort of controller.

I mean, with them off in DC mode im assuming that once they get to a certain temp they will kick in? and if so then that doesnt sound too bad.

I have that thermal sensor program (think it is called AI suite or something) which tells me the temps are all below 40 all over the mobo. Might try stressing it to get the temps up and see if that turns the fans on.

doyll · 10 Jul 2016 at 18:35

The 2x fans you have are 1x PH-F140SP and 1x PH-F200SP. The 1st is a very good fan. The 2nd is .. well .. not a fan I will use.
I love Phanteks products, but the PH-F200SP is not a good fan, full stop. I've tested it, tried to use it in Enthoo Luxe case, and just one of those 'dogs that just ain't gonna hunt' kinda deals.

I'm not familiar with your Z97, but some newer mobos have settings that allow fans to not run a low load settings. Hopefully someone with knowledge of your board will be here this evening.

Fernanjoe · 10 Jul 2016 at 18:39

Nice one cheers buddy. Good to know about the fans. I will most probably take out the rubbish one then and buy a new one for the front intake.

doyll · 11 Jul 2016 at 10:23

I lied. I use my PH-F200SP at my desk in hot weather to create a little airflow. It does it quietly with not too much airflow so paper don't blow around.

Tealc · 11 Jul 2016 at 12:45

If you nudge the fans to get them started do they stop after a few seconds or continue for a while/forever?

There should be a way to adjust threshold and fan response in BIOS. It could be something over simplistic like Silent, Normal and Turbo. There should also be a method to link the fan header to a temperature sensor.

There's no need to replace good 3 pin fans with PWM variants as there are ways to control 3 pin fans via PWM.

Fernanjoe · 11 Jul 2016 at 16:09

Hi Tealc, Ill have a go at giving the fans a nudge when I'm home tonight.

I did set them to DC in the bios which had a few of the options you mention - I set the profile to silent so maybe that isn't the right thing to do.

Ive gone ahead and ordered a new fan to replace the large 200mm one. Ill probably play around with a few settings and see what feels best for temps Vs Noise.

Cheers for the advice, appreciate its never easy commenting on someone else's build.

Troezar · 12 Jul 2016 at 06:28

Tealc said:
There's no need to replace good 3 pin fans with PWM variants as there are ways to control 3 pin fans via PWM.

That is good news as I have 6 Gentle Typhoon fans that were a group buy on Overclock.net but turned out to not be PWM. Custom order so I'd like to use them. How do I get them to work with PWM?

Fernanjoe · 12 Jul 2016 at 18:29

Hi again. Just wanted to say i got my new fans today so i swapped out that large 200mm one and the system is now loads quieter so i think im happy and wont bother playing around with the rest of the settings. Cheers for the advice.