140mm PWM fans which will STOP

Associate
Joined
3 May 2018
Posts
604
Hi,

I know this question has the long pedantic answer, so I'll try and address that.

I know the motherboard and/or fan controller has to be configured to allow full stop 0 duty cycle PWM. I know the fan does not have to support it under the spec. However I know that some fans WILL stop when sent 0 duty cycle and others will not.

For example. NZXT radiator fans, will not stop, nor will their pumps. They will idle at around 800-1000rpm instead. The only way to stop them is to cut the power to the fan header.

Corsair rad fans are similar.

The motherboard will NOT allow you to configure the main CPU fan or pump headers to 0rpm anyway.

However the Artic F14 PWM fans I have in a previous system WILL stop dead at 0 PWM. They also start fine when raised to 20% duty cycle without stalling or 'cogging'.

The F14s seem hard to get these days with sellers selling them at £20 each. The new one is the C14? There is no documentation as to whether or not they support full stop. I have read that they disabled that full stop functionality before people (stupid people) were returning them as DOA. That would be extremely disappointing.

These are for case fans. They are only required to be running at all under high loads to suppliment airflow for the twin main radiators.

2 intakes in the basement to try and pull as much air through the floor filter when the GPU rad fans are at full tilt, to stop dust being pulled in everywhere else.
1 exhaust at the VRM section to add additional airflow over the VRM section when the CPU rad fans (and thus CPU) are working hard.

EDIT: Mobo is a Crosshair VIII Wifi. Case is a define 7. So I have 8 fan headers, 2 pump headers and a PWM multiplexer in the case if those aren't enough! I have BIOS sensible boot defaults for fans and then have Argus Monitor and MSI afterburner taking over when windows boots.
 
Last edited:
Don
Joined
19 May 2012
Posts
17,140
Location
Spalding, Lincolnshire
Arctic F14 PWM aren't hard to get hold of - OcUK stock them so no need to mention competitors!

However I'm not sure any of the current Arctic Fan's actually have a 0rpm mode - It sounds like the best option would be to get a stand alone fan controller and bypass the motherboard control entirely

My basket at OcUK:

Total: £16.69 (includes delivery: £8.70)​



 
Associate
OP
Joined
3 May 2018
Posts
604
The fan controller is irrelevant. The Hero has plenty of ability.

The F14s I bought 4 years ago did not claim to support below 200rpm either, but they do.

However, even their current documentation says 200rpm min.

Additionally the P14s are either PST, CO or both and even boast about "switching to efficient passive control below 5% PWM" and running lower RPMs at 40% because of the motherboard restriction on CPU headers. Both in the opposite direction to "just turn the fan off please."

I don't have to use the CPU header at all. I can run the rad fans on a chassis fan header. I mean the thing will boot and run fine with all the fans shut off. Just not exactly performantly.

So I'm worried about fan header limitations, I'm comfortable I can send them all 0% PWM.

I suppose I'm asking, has anyone tested a fan recently which will stop when sent 0% PWM, rather than do you know ones that "say" they support it.

One limitation is, I don't believe you can switch a fan from being PWM to being DC anywhere but bios. Automating it such that it switches to DC at 20% and thus 0V at 0% ... I'm not aware of how to do that.... not without doing it electronically myself... which I have considered. A PWM adapter which just cuts power to the fan entirely below 20%.

I removed the competitor reference.
 
Associate
OP
Joined
3 May 2018
Posts
604
From the RMI stand point I can see what they are up against though.

If you are not aware of the difference between a PWM fan and a DC one, and you buy your new fan (PWM) and stuff it into a DC header... if that fan supports 0 rpm. It will NOT START. As it sees 0% duty cycle on the control pin.

So little Johny fires it back as Dead on arrival.
 
Associate
Joined
19 Jul 2015
Posts
485
...you buy your new fan (PWM) and stuff it into a DC header... if that fan supports 0 rpm. It will NOT START. As it sees 0% duty cycle on the control pin...
It's the other way around. The PWM pin is, per the spec, pulled up internally, so if it's not connected then the fan runs at 100%.
 
Associate
OP
Joined
3 May 2018
Posts
604
I can confirm that my EK-Vardar EVO 140s (both RGB and non-RGB, bought last year) will stop when the PWM signal is below around 25%. Start up at minimum RPM no problem when just above that.

Thanks. I see their 120s even advertise 0db regime. Pricey though. Then again EK can't really be beaten for radiators so their fans should be good there. Maybe something cheaper for the case fans or I'll be hitting over £150 in fans alone!
 
Back
Top Bottom