what is the correct way to install pc fans

reyinqu
reyinqu used Ask the Experts™
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What is the best way to install fans in a pc: to  supply air inside the case or to remove air from the case.  What happen if all fans are set to remove air from the case?  What happen if all fans are set to supply air to the fans.  
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Most Valuable Expert 2015

Commented:
In the long run it probably won't make much of a difference, as long as there are enough vents the air will circulate whether you blow in or out.

From a physics point of view, since cool air is heavier than warm air, you should best get an airflow that sucks in the cool air at the bottom of the case and lets it exit the case at the top.
Top Expert 2012
Commented:
You generally want the same number of fans moving air into the case as moving air outside the case.  Since the power supply generally has a fan removing air from the top of the case, installing an intake fan near the bottom is best.  If you set all the fans to move air in or move air out, the air will not be moved efficiently - when this happens, temperatures will be higher than a case with good airflow.
Dr. KlahnPrincipal Software Engineer

Commented:
From a physics point of view, since cool air is heavier than warm air, you should best get an airflow that sucks in the cool air at the bottom of the case and lets it exit the case at the top.

I agree with this ... unless you have a cat, in which case the system will instead be sucking in cat hair at the bottom, and collecting it inside the case for its own dark and nefarious purposes.
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Top Expert 2013

Commented:
normally the best way is to create a draft, meaning in most cases the air is blown in on the front side, and out on the backside (power supply and case fan)

blowing only in or out will not have good cooling effects, and lower the air volume handled by the fans considerably, by creating an over, or underpressure situation

Author

Commented:
My PC already have a fans at the front and at the back.  At the botton is the power supply fan.  I only had two remaining spaces available.  I placed one fan at the rear side (supply fan inside the case -above mother board) and installed the other fan to extract air at the top.  Is that a good arrangement ?
Top Expert 2013

Commented:
could you post the setup?  see what i meant in drawing
Pc-casePower-supply.docx
yes, that sounds like a good setup,

On Dells, both fans in the back blow out extracting hot air from the case, this is important to you if you have a dell since the rear fan has a shroud that pulls heat from the processor and dumps it out the back of the unit.
Top Expert 2012
Commented:
It depends on which way the fans are blowing - the best way to set them up is have as much air in the case being moved from one side to the other, which usually means intake on one side and exhaust on the other.
Mohammed RahmanSenior Operation Specialist
Commented:
I would go with rindi:
Install a 120mm fan (if possible) at the front bottom and a rear exhaust at the top. Its a good practice to install a FAN as exhust for the cabinet than depending on the PSU fan. Try install the exhaust close to the processor and gpu heatsinks. If uour case have enough room, install two exhausts close to CPU and GPU heatsinks. Also make sure that there are no obstacles like cables or the HDDs near the intake FAN at the bottom front. With this setup, the cool air will be sucked from the front, it will be then easily sucked by the CPU and GPU fans and it will exit out of the rear fan/fans. ** Cable management is quite important and if managed neatly, it will contribute drop few degrees :)
Top Expert 2013

Commented:
any feedback reyingu ?

Author

Commented:
Attach drawing of fans nobus.  How can the cable management affect the temperature.  What is a good temperature?
Pc-casePower-supplyRey.docx
Most Valuable Expert 2015

Commented:
Cables, particularly the wide IDE or SCSI cables, can hinder airflow. For that reason you can also get IDE cables that are packed round, so they can't easily block the airflow anymore. With today's SATA cables which are very thin that isn't a big problem anymore.
Top Expert 2012
Commented:
A good temperature is one that is not far from room temperature - if it isn't, you aren't moving the hot air out fast enough.
Top Expert 2013

Commented:
what i do is route the cables together with cable straps, to reduce the volume they use

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