Question Bottom case fan, Noctua NF-A15, better as intake or exhaust in Fractal Torrent Compact (which already has 2x180mm front)?

Mar 26, 2022
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I have the following setup:

Case: Fractal Torrent Compact (two front fans 180mm, which I think are intakes)
CPU cooler: Noctua NH-D15S with one fan (Noctua logo facing the rear side of the case)


I have two questions about what I should do with my Noctua NF-A15 fan which I luckily got for a very good price. It won't fit as a rear (too big) or top fan (too many cables and drives there)

- Should I install the NF-A15 as exhaust or intake if it's supposed to be at the bottom?

- What is the correct direction? Logo facing towards the ground (towards the outside of the case) would be considered exhaust?

I'm attaching three images of the fan and Noctua's instructions, but I don't think I understand exactly in which direction they'd be intake/exhaust

 

Lafong

Respectable
Look VERY closely around the edges of the Noctua fan frame.

You will see an arrow pointing in the direction of air flow.

The fan will spin ONLY in one direction, regardless of where you put it.

That model is good as either an exhaust or an intake. OK, but not best if mounted directly onto a tower cooler.

If you put it on the front side, you'd want the arrow pointing toward the case interior.

If you put it on the back side, you'd want the arrow pointing to the case exterior.

In either case, it would be moving air from front to rear. Blowing in if in front, and sucking out if in back.

If it's too big for the back side, then put it on the front as an intake.

If the front is already occupied by other 180 mm fans, then the bottom of the case would be your only choice. The arrow points in the direction of airflow.

I think case bottom fans are typically mounted as intakes, but they may not help temps much.

Fractal documents indicate bottom mount is intended as intake.
 
Last edited:
Mar 26, 2022
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Look VERY closely around the edges of the Noctua fan frame.

You will see an arrow pointing in the direction of air flow.

The fan will spin ONLY in one direction, regardless of where you put it.

That model is good as either an exhaust or an intake. OK, but not best if mounted directly onto a tower cooler.

If you put it on the front side, you'd want the arrow pointing toward the case interior.

If you put it on the back side, you'd want the arrow pointing to the case exterior.

In either case, it would be moving air from front to rear. Blowing in if in front, and sucking out if in back.

If it's too big for the back side, then put it on the front as an intake.
Thanks, that really cleared it for me. But like I said, front already has two 180mm which work really well. The case is super silent already and I'm happy with the temps. The only place I have for this 150mm Noctua fan is really at the bottom of the case. But I'm not sure if I'd see any meaningful temp drop if I place it there. Maybe I should just return it? I thought it's a good deal for $22 and I initially wanted to install it as a second fan on my NH-D15S CPU cooler, but my RAM sticks are so tall that the fan won't cover almost half of the CPU cooler...
 

Lafong

Respectable
Thanks, that really cleared it for me. But like I said, front already has two 180mm which work really well. The case is super silent already and I'm happy with the temps. The only place I have for this 150mm Noctua fan is really at the bottom of the case. But I'm not sure if I'd see any meaningful temp drop if I place it there. Maybe I should just return it? I thought it's a good deal for $22 and I initially wanted to install it as a second fan on my NH-D15S CPU cooler, but my RAM sticks are so tall that the fan won't cover almost half of the CPU cooler...
See my edited reply above.

Fractal says the bottom mount is intended to be an intake.

It may not help your temps at all. Experiment.

You might exchange it for a 120 mm model and add that to the DH15S if that would help RAM clearance, but don't expect that to lower your temps by more than 1 or 2 degrees.

It's a fine fan, but if it is 150 mm, that is an odd size that won't fit in most locations. I've got 2 Noctua 120 mm fans running around 500 rpm. Very quiet.
 
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DRagor

Illustrious
Should I install the NF-A15 as exhaust or intake if it's supposed to be at the bottom?
Bottom is always intake. I can't imagine build in which bottom exhaust would make sense.
What is the correct direction? Logo facing towards the ground (towards the outside of the case) would be considered exhaust?
Already answered by Lafong in detail
But I'm not sure if I'd see any meaningful temp drop if I place it there. Maybe I should just return it?
Not for CPU. However it could help with GPU temps if you have it. If you don't have GPU or it is cool enough then I would say return it.
 
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Mar 26, 2022
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Not for CPU. However it could help with GPU temps if you have it. If you don't have GPU or it is cool enough then I would say return it.
That's a great hint! Thanks. Is there a controlled way of reliably testing GPU temps with and without this fan? I can't really think of a way where all factors would be controlled so as to produce accurate results to draw correct conclusions from!

What would be the expected temp drop for the GPU in your experience? Probably not more than 2-3 degrees? If even that.

I have an EVGA FTW3 RTX 3070 Ti (335w max power limit) by the way.
 

DRagor

Illustrious
Is there a controlled way of reliably testing GPU temps with and without this fan?
That's no big science. Play GPU challenging game for an hour, note highest achieved GPU temp. Install fan, repeat test, compare the results.
What would be the expected temp drop for the GPU in your experience? Probably not more than 2-3 degrees? If even that.
Can't say I did such tests. However, your GPU does get generate lots of heat so it may be worth trying. Getting even 5 C less on maximum temps would be good result.
 

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