Question Using a 140mm CPU cooler fan as a case fan?

[35below0]

I've got a NH-D15 tower cooler attached to a i5 13600K. I'm only using the single fan because space in the case is a bit tight. It is physically possible to attach the second fan, but it's very tight.
So the optional fan is doing nothing atm. And that's ok, because it is optional anyway and the CPU doesn't need it.

I've got an unused fan slot on the top of the case (Fractal Design North). And i'm thinking of using the optional NF-A15 fan as a top mounted exhaust fan.

Is this a silly idea? Should i buy a 140mm case fan? Or just not bother? Temperatures are fine and there is no noise problem.
The only reason i'm thinking of doing this is because i've got a fan that's doing nothing. I can always attach it to the cooler later if it becomes neccessary.

Noctua's blurb says: "The NF-A15 is tailor-made for use on today's high-end CPU coolers: While its 150mm width matches blah, blah, blah, heatsinks, its 140mm height yadda, yadda, case compatibility. The NF-A15's standard 120mm mounting holes (105mm spacing) also make it an ideal performance upgrade for 120mm case or CPU fans."

So it should be fine to do this, but please check my head.


Additional question: Should i hook up all case fans to individual MoBo headers, or use a case hub? Would PWM be sillier if i used multiple headers? Or is the hub simply for controlling multiple fans using one curve/setting?

Thank you.


Case: Fractal Design North, with two 140mm front intake fans, and no exhaust fan (default North config). I will be adding a 120mm exhaust fan very soon, a Noctua NF-S12B Redux-1200 PWM. That is a slower fan, designed for case ventilation.

CPU: intel i5 13600K (not overclocked)

GPU: 4060, Gigabyte Eagle OC (not overstressed. not even stressed)

Motherboard: Gigabyte Z790 UD

 

[Crowii]

I've got an unused fan slot on the top of the case (Fractal Design North). And i'm thinking of using the optional NF-A15 fan as a top mounted exhaust fan.

Is this a silly idea? Should i buy a 140mm case fan? Or just not bother? Temperatures are fine and there is no noise problem.
The only reason i'm thinking of doing this is because i've got a fan that's doing nothing. I can always attach it to the cooler later if it becomes neccessary.

An unused fan slot and/or fan is not a problem if cooling isn't a problem. It'd be for aesthetic reasons, and since it's an NF-A15, it sure ain't that.

Additional question: Should i hook up all case fans to individual MoBo headers, or use a case hub? Would PWM be sillier if i used multiple headers? Or is the hub simply for controlling multiple fans using one curve/setting?

Got enough PWM headers for the amount of fans? No problem in just using them.
Don't have enough? Get a hub.
Care about cable management enough? Get a hub.

 

[35below0]

An unused fan slot and/or fan is not a problem if cooling isn't a problem. It'd be for aesthetic reasons, and since it's an NF-A15, it sure ain't that.

That's true. 👍 Case doesn't have a glass panel either way.

I have enough headers and a hub. So i guess i'll toss a coin.

 

[punkncat]

The fan is not aware of what it is cooling and has the same connector...

 

[Paperdoc]

When comparing "Pressure Fans" used for CPU's and rads to "Air Flow Fans" used for case ventilation, there are two differences. AT LOW backpressure (that is, little interference in air flow path to resist air flow), the Air Flow fans will deliver somewhat greater actual flow for the SAME speed setting. At high backpressure (like the fins of a rad or heatsink) the Pressure Fan will deliver more air flow. For your situation using this Pressure Fan as a Case Vent fan is just fine - the small difference in air flow will not be any issue for you.

Air flow balance is important in a case. Ideally you want intake air capacity to match or slightly exceed exhaust air flow capacity. Recognizing that what comes in must go out, a slight intake CAPACITY excess means that the air PRESSURE inside the case will be just slightly higher than outside. That means that, at cracks in the case where air can leak, the direction of leakage will be from inside to out, and that prevent your case from sucking in unfiltered air that may bring in dust.

You describe a case with two intakes and no exhaust fan, but plan to add a Noctua NF-S12B Redux 120 mm rear exhaust fan. The two front 140 mm fans included with the case have max air flow ratings of 132.5 m³/h each (total 265). Because they are behind dust filter sheets their actual max air flow will be a little less. The planned 120 mm Noctua has a rating of 100.6 m³/h max. IF you add the Noctua NF-A15 in a top rear location its rating is 115.5 m³/h max, so that would total 216 m³/h exhaust capacity. I would consider that combination a good match to the front intake fan capacity. So go ahead and do that - it will give you very good overall case air flow.

 

[geofelt]

Good looking case.

I am not a fan of adding top exhaust fans.
Particularly strong ones.
I think they tend to divert the front cooling airstream up and out of the case before reaching the cpu cooler and the graphics cards.
I would install a 120mm rear exhaust to direct the airflow.

Of course, you could experiment.

 

[35below0]

Thank you very much for your answers. You've actually given me a lot of food for thought.

I decided not to go ahead with the top mounted fan installation because it seemed unneccessary. But Paperdoc's reasoning is sound, even with geofelt's objection.
I still have time to decide as the new 120mm fan hasn't arrived yet.

I'm slightly baffled by Fractal Design's decision not to include any rear exhaust fans at all, and so were all reviewers of the case.
Here's THG review - https://www.tomshardware.com/reviews/fractal-design-north
I would disagree about it's price being "fair" if fair means less expensive. It's not madly expensive but i paid 160 euros for it. I only did it because i liked the look that much.
Initially i dismissed this case the moment i saw it. But then i came to realize i like the other choices less and less. I could have taken a Define 7 by the same manufacturer but it offered more features than i needed. ...so i paid more money for a case that wasn't as feature-rich. And had oak. *sigh*
I also disagree about it being noisy btw. Though that mostly depends on the GPU fans i guess.
Idle/web browsing noise is inaudible.

Anyway, back to the no exhaust fan situation. One possible reason is dust?
The case has a mesh panel on the side and top (there is an optional glass panel). The rear panel is almost 50% holes for air to leak out of, so there's certainly plenty of "cracks" for air to find.

Other reason is FD being cheap of course. Or maybe they think that anyone in need of an exhaust fan would take their Aspect fan off in favor of another manufacturer.

Thanks again for the advice.

Good looking case.

I am not a fan of adding top exhaust fans.
Particularly strong ones.
I think they tend to divert the front cooling airstream up and out of the case before reaching the cpu cooler and the graphics cards.
I would install a 120mm rear exhaust to direct the airflow.

Of course, you could experiment.

CPU cooler orientation might make a difference. If the CPU cooler is kicking hot air upwards and out, then a top mounted fan would assist in kicking air out. The GPU fans, CPU fans and top fan form a chain.

I'm not sure how common that configuration is.

 

[Paperdoc]

Top exhaust fans MAY tend to pull air up in the case. But one version of them definitely IS a problem. The top FRONT position, especially if there is a front fan right at the top, will rob all that top front fans intake air right out in an air "short circuit". That is why I said you should mount your top fan at the rear position.

 

[Satan-IR]

My experience says front bottom intake and top rear exhaust do actually help airflow. Regardless of the fan being a pressure one or an air flow one. Of course they are different types of fans but when it comes to makeing a few degress of temp change in the case those differences are somewhat negligible and meaningless. Mind you, a lot depend on what's inside and how they're arranged too.

For example, in some situations a graphics card is so big that with the side panel closed it practically cuts the compatment in the case into two nothern and southern separate spaces. Another factor (under load) is whether the PSU has a fanless mode or not and if for example the user has had to attatch the PSU (because of short cables) in a way that it actually exhasts warm air into the case.

Some cases also you have difficulty moving air inside because of the size and how drive cages are attached in there and when they're populated they actually hinder air flow.

A PWM header is the same reagardless of what you want to do with the fan. You can set profiles for each fan with relevant apps and PWM ones are usually better at fine-tuning a certain RPM with small increments for example than voltage regulated ones. Doesn't the MOBO have software/app/suite to set fan curves/profiles and such?

TL;DR I would typically (considering all of the above) do front bottom in and rear up and or top out with the intake pressure a little than output.

 

[35below0]

Top exhaust fans MAY tend to pull air up in the case. But one version of them definitely IS a problem. The top FRONT position, especially if there is a front fan right at the top, will rob all that top front fans intake air right out in an air "short circuit". That is why I said you should mount your top fan at the rear position.

I was planning on using the rear position, thanks.

Doesn't the MOBO have software/app/suite to set fan curves/profiles and such?

TL;DR I would typically (considering all of the above) do front bottom in and rear up and or top out with the intake pressure a little than output.

I have two front 140mm fans pre-installed so i don't want to break up their partnership in order to setup front bottom + rear up. But it's good advice.

Yes, the motherboard is a Gigabyte Z790 UD and i am using Gigabyte Control Center. Not overclocking, just installing updates and monitoring fans/temps.
Fan settings are left in their default "silent" position. "normal" just makes them spin faster and louder but i don't need the cooling benefit.
GCC is pretty ok. It's a little bloated and i'm not a huge fan but it does what it's supposed to without fuss so, ok.

And now for some pictures.

https://imgur.com/a/NFyQvnU

View: https://imgur.com/a/NFyQvnU


Looking at it all, and taking into consideration all the advice, the sensible thing to do with the optional Noctua NF-A15 CPU fan, is to attach it onto the tower. And let it blow air upwards and out.
Heck, i'm not even sure i need a rear exhaust fan then? It would help pull some air onto the CPU and GPU, so there's that.

But i'd like to stress once again that i have no temp. problems whatsoever. It's fine the way it is.
I would not even be buying a rear exhaust fan except i'm buying a new PSU and replacement fan for an older PC. So i added one more fan to my purchase.

And in case you missed it, yes i *did* accidentaly install the CPU cooler fan so that it blows air onto the GPU.
🙄

Edit - In the North, the HDD/SSD trays are located under the PSU shroud. There is one HDD inside, but doesn't affect airflow.

https://imgur.com/rWrDKLC

View: https://i.imgur.com/rWrDKLC.jpg

 

[Paperdoc]

Thanks for giving the Solution label.

 

[Satan-IR]

Looking at it all, and taking into consideration all the advice, the sensible thing to do with the optional Noctua NF-A15 CPU fan, is to attach it onto the tower. And let it blow air upwards and out.
Heck, i'm not even sure i need a rear exhaust fan then? It would help pull some air onto the CPU and GPU, so there's that.

Yes that sounds good.

Although you can try and see how much of a difference it makes to add the fan on the back of the case behind CPU cooler/fan.

After you've rotated the cooler/fan 90 degrees clockwise, for sure. That way it'd help exaust the warm air from CPU cooler and the warm air from the graphics card fans blowing towards the CPU through card sink grill. My guess is it'd help CPU temps go down an average of 2-3 degrees.

And in case you missed it, yes i *did* accidentaly install the CPU cooler fan so that it blows air onto the GPU.

Yes I was actually going to mention the cooler/fan orientation until I reached this part.