Can motherboard set fans to run below 40% speed?

[thtran6]

Hi guys,

So I'm currently running four Noctua NF A14 ippc3000 fans in my case.
All of these fans are pwm fans and they are connected directly to the motherboard's 4-pin fan headers.
The motherboard I'm using is MSI Z370 A-pro.

So Noctua indicates that this particular type of fan has a minimum speed of 800 rpm (+/- 20%), which is a lot lower than 40% of the fan's maximum speed (3000 rpm).

My question is: is my motherboard able to set these fans to run below 40% (or even 30%) of their speed?

(P/S: I'm asking because I read somewhere that some motherboards' pwm control will not allow fans to run below 40% or 50%. I'm not sure if this is right. But if this is the case, then setting my fans to run at 30% of their speed will cause any danger to the fan itself or to the motherboard?)

 

[Darkbreeze]

All you can do is try. I don't have a Z370-A Pro board to test it on, but I have those exact fans, and several other Noctua fan models including the standard NF-A14 and NF-A14 iPPC 2000 RPM models, and on the ASUS and Gigabyte Z170 and Z270 boards I have here I have been able to set them down to about 25% without them stalling.

I generally run my 2000 RPM models at 35% because at that speed they are still very quiet, DO move a fair amount of air and they are capped at about 85% maximum RPM because above that I don't see any decrease in thermal performance. They seem to hit a plateau at that RPM in this case. Plus, they are much quieter at a maximum of 85% than at 100% so why run them at annoying levels when there is no or not much gain from it.

I think your board can probably do the same as these boards as yours also has the option to choose PWM or DC mode for any connected fans whether they are 3 or 4 pin models, and most of these boards regardless of brand have very similar PWM control hardware. The fact that the fan is capable of not stalling at a 20% PWM signal further bolsters the idea that it should be capable, but again, I think around 25% would be where you will most likely begin to see issues with stalling.

If your board has an auto-optimization capability for fan controls I would avoid using that, and please don't confuse that with using one of the smart fan controls because that's entirely different. Some boards can automatically detect minimum and maximum RPM and auto configure for those parameters but so far on these higher end Noctua fans I've found that it's not accurate and tends to not allow you to run fans at less than 40% afterwards. If you've already run that optimization procedure I'd reset the bios to default values and then configure the fans at the curve you want with the minimum you want and then try it.

If you have issues with stalling or if they have trouble starting up then increase the bottom RPM by a few percentage points and try again.

 

[thtran6]

All you can do is try. I don't have a Z370-A Pro board to test it on, but I have those exact fans, and several other Noctua fan models including the standard NF-A14 and NF-A14 iPPC 2000 RPM models, and on the ASUS and Gigabyte Z170 and Z270 boards I have here I have been able to set them down to about 25% without them stalling.

I generally run my 2000 RPM models at 35% because at that speed they are still very quiet, DO move a fair amount of air and they are capped at about 85% maximum RPM because above that I don't see any decrease in thermal performance. They seem to hit a plateau at that RPM in this case. Plus, they are much quieter at a maximum of 85% than at 100% so why run them at annoying levels when there is no or not much gain from it.

I think your board can probably do the same as these boards as yours also has the option to choose PWM or DC mode for any connected fans whether they are 3 or 4 pin models, and most of these boards regardless of brand have very similar PWM control hardware. The fact that the fan is capable of not stalling at a 20% PWM signal further bolsters the idea that it should be capable, but again, I think around 25% would be where you will most likely begin to see issues with stalling.

If your board has an auto-optimization capability for fan controls I would avoid using that, and please don't confuse that with using one of the smart fan controls because that's entirely different. Some boards can automatically detect minimum and maximum RPM and auto configure for those parameters but so far on these higher end Noctua fans I've found that it's not accurate and tends to not allow you to run fans at less than 40% afterwards. If you've already run that optimization procedure I'd reset the bios to default values and then configure the fans at the curve you want with the minimum you want and then try it.

If you have issues with stalling or if they have trouble starting up then increase the bottom RPM by a few percentage points and try again.

Cool glad to hear that these fans can be run at 25%. I'll give them a try.
Btw, do you know if DC control will be different from PWM control with regard to minimum fan speed?
Like, if you set pwm for the fan at 30% it will not run,
but if you do it in DC mode and adjust the voltage to a proportional value corresponding to 30% fan speed, it will run? Just curious.

 

[Darkbreeze]

The thing about that is, I personally (And I don't know for sure if this is 100% accurate or not, it's just what I "feel" is right based on working with motors in general) feel like running a PWM fan in DC mode is bad for the motor. PWM fans are assembled using motors that are probably intended to be used with a straight 12v, rather than a lower voltage like a voltage controlled fan. So it stands to reason that running them at lower voltages may tend to be bad for the motor itself, much like running any motor at a lower voltage than it was designed for unless it is a variable voltage motor.

Obviously, PWM works differently with a straight 12v signal that gets turned on and off rapidly, but is STILL always at 12v, rather than by reducing the voltage to control fan speed. I know it will work, because I've run PWM fans in DC mode, but it seems like the motors sounded wrong when doing so.