Fractal Design Define S Fans

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Bedwards923

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Oct 6, 2012
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Hey everyone,

I bought a Fractal Design Define S windowed case and I am in the process of selecting fans. The case comes with two 140 mm fans, which I am going to use for exhaust at the rear and top. I wanted to add three 140 mm intake fans to the front, but I am unsure if it will fit. If not, would it be better to go with three 120 mm or two 140 mm fans?

Thanks!
 
Solution
JackNaylorPE
It's just math. But again, the fog machine shows 2 and 2 is not functional as it draws the fog (and heat from the 650 watt PSU and 200 watt GFX card) right back into the case. 3 in and 2 out is neutral ... fog blown at the case rear doesn't move that much.

4 in and 1 out shows a nice air flow and fog blown behind the case is briskly swept away from the case. And, perhaps more importantly, more fans at slower rpm is much quieter than less fans at higher rpm. if you can keep ya fans at 850 rpm or less, which you can with 50 - 75 watts per fan, the system, with any decent fan, will be inaudible.
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Positive.negative doesn't really!have any bearing on temps mate - its more a means to minimise dust entry into the case.

In a case like the define series where all intakes are filtered its not a necessity

2x140mm intakes & 2x140mm exhausts in honestly more than enough for any setup.

What board are you using , how many 4 pin headers does it have ??

That would influence my buying more than anything else.
 
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Intake fans will have their performance impacted by the air inlet filters... not so much when perfect;ly clean by significantly so when dusty. Here's a couple of rules of thumb

Let's give a specific 120mm operating at xxxx rpm a value of 1 ... in context, same design, same rpm, same everything else

120mm exhaust fan = 1.00
140mm exhaust fan = 1.33

120mm intake fan = 0.67 (dusty filter)
140mm exhaust fan = 0.89 (dusty filter)

here's your options according to newegg product specs
https://www.newegg.com/Product/Product.aspx?Item=N82E16811352055

Top: 3 x 120/140 mm fan (not included)
Bottom: 1 x 120/140 mm fan (not included)
Front: 3 x 120/140 mm fans (included is 1 Fractal Design Dynamic GP14 fan, 1000 RPM speed)
Rear: 1 x 120/140 mm fan (included is 1 Fractal Design Dynamic GP14 fan, 1000 RPM speed)

So yes it will fit up to 8 140mm fans

Now lets look at your situation....

2 140mm exhaust = 2 x 1.33 = 2.66
3 140mm intake = 3 x 0.89 = 2.66

So on day 1, you will be fine, with no dust in the filters, you will have positive case pressure. As these filters get dusty tho, things get less favorable. While most folks will tell you that negative case pressure is a bad thing cause it sucks in dust thru unfiltered openings, what most often goes unsaid is that the most common entry point of that dust is the rear case grille and vented slot covers. And along with that dust comes all the hot exhaust from your PSU and GFX card.

The other rule of thumb we use is that for a quiet system, you'd want one 140mm fan for every 75-100 watts of heat (50-75 for 120mm). Assuming an over clocked system, CPU (130 watts) GFC Card (200 watts) MoBo (30 watts) Everything else 35 watts = 395 watts. So 5 fans would give you 375 watts of cooling. In your situation, i think I would go with:

(3) front Intake fans
(1) bottom intake fan
(1) rear exhaust

With 4 intake fans, you would always have positive case pressure, even with dusty filters. There would be no dust intake and there would be no PSU / GFX card exhaust sucked into the case. Remember, "matching" the number of intake and exhaust fans serves no purpose. A kitchen exhaust fan has no matching intake fan ... an attic fan s no matching intake fan ... your car has an intake fan for the engine, no exhaust fan. To cool a room, a fan in one window and a open window provides all the ventilation needed. The differential pressure created in the case by the fans is all that is needed to induce ventilation.

Positive.negative doesn't really!have any bearing on temps mate - its more a means to minimise dust entry into the case.

2x140mm intakes & 2x140mm exhausts in honestly more than enough for any setup.
Click to expand...

Theoretically that's true.... practically however, when the 650 watt PSU and 200 watt GFX card are located adjacent to the primary entry point, you are sucking much of that hot exhaust right back into the case. Here's the fancy test equipment we used to monitor this :)

https://www.amazon.com/Chauvet-Hurricane-700-Fog-Machine/dp/B0002D0JX8

Two in and two out is a negative pressure situation as soon as dust begins to accumulate on the filters. In building ventilation, we use differential pressure manometers to measure pressure loss across filters. As dust builds up on the intake louvers, the difference in air pressure makes doors difficult to open.... or if on the other side, smack ya in the face.




 
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It's just math. But again, the fog machine shows 2 and 2 is not functional as it draws the fog (and heat from the 650 watt PSU and 200 watt GFX card) right back into the case. 3 in and 2 out is neutral ... fog blown at the case rear doesn't move that much.

4 in and 1 out shows a nice air flow and fog blown behind the case is briskly swept away from the case. And, perhaps more importantly, more fans at slower rpm is much quieter than less fans at higher rpm. if you can keep ya fans at 850 rpm or less, which you can with 50 - 75 watts per fan, the system, with any decent fan, will be inaudible.
 
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Solution


I understand the math 100% but there are too many variables to make anything acually factual out of it.
Its entirely case dependant ,as long as non used fan vents & intakes are filtered there isnt going to be any issue at all
How many people run 4 x 140mm intakes seriously ??
2 front intakes,2 rear exhausts,run the exhausts 200rpm slower - job done.
 
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