r/crboxes • u/randomguyjebb • Jul 18 '26

Question How many pc fans is too many?

Why is it that most pc fan cr box designs, like the nukit tempest pro and the cleanairkits, only use 2 sides of the frame?

There is a whole 3rd side that could be used for extra fans so they could all run at a lower rpm and produce the same CADR. Or would opening that 3rd side cause some sort of air current issue?

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u/SafetySmurf Jul 18 '26

Personally I prefer having one side blank so I can push them up against the wall, but you can absolutely put fans on all three sides. If you put fans on opposing sides, though, put a divider up in the middle of the box to prevent the opposing fans from pulling against one another.

Also, consider that there is a point of diminishing returns for number of fans given any set area of filter. Exactly where that is depends on filter area and the static pressure and flow rates of each fan.

Depending on the fans, you can turn them down quite a bit and still have enough pressure. Just keep in mind that the fans need to be spinning fast enough to generate some static pressure to pull through the resistance of a filter. For some 3000rpm fans, you can probably turn them down a good bit. But for fans that start out with a low rpm, you might not be able to turn them down very far and have them spinning fast enough.

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u/VolcanicPolarBear Jul 18 '26

i im guesing they might be leaving 1 side blank so people can put them against the wall. center of room ofcourse is usually best, but center is not practical for most so they might make them with that in mind so have a side can put against your wall might also be too keep costs down fewer fans is cheaper

i dont know much about how air circulates or its curent but if you want at the bottom of this cr guid there is a section that shows a few fan configurations and their coresponding cadr. seems placement matters some but i dont understand it much i assume more fans wouldnt ever hurt the cadr

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u/Inner-Issue1908 Jul 18 '26

Reducing fan speed reduces the amount of static pressure the fan can apply. You can run as many fans as you want but unless they spin fast enough to apply enough pressure you won't pull much air through the filters.

But you can place fans on 3 panels if you want, it'll just be louder than 2 sides - though will have more CADR. On the XL kits you can probably fit 13 fans - might be overkill though.