How Much Cooling Really Helps?

This is going to be sort of a broad question, but there seems to be two sides of an argument: one says that the more fans and better cooling you have, the longer your system will last. Then there's this other side that says you only need what's necessary, because before any part of your computer will break down from being too hot for too long, you'll have probably replaced it or got a whole new system anyway.

Is an extra fan or two only really needed if your temperatures are TOO, or "dangerously" high, to the point that it will noticeably have problems or even overheat? Or does having an extra cool system do anything to actually improve your system?

I got this new case that supports up to 9x 120mm fans, more than my previous case, but my temps don't seem to be any better. Sometimes it seems as if having all these extra noisy fans aren't doing anything to actually cool down the system noticeably. Like, why have them there and produce all that extra noise? I dunno, is what I'm asking making any sense at all? It's sort of just a broad series of questions regarding PC cooling, what's necessary and what is too much.

There are variables to cooling your machine. The old case may have been more efficient in moving air than the new case. 9 x 120 fans may not all be placed/pointed in the most optimal way. The temperature around the case (read room temperature) may be different from one temp reading to the next.

I like to use lots of slow moving fans that help each other out. The slow speed keeps noise to a very low minimum. By making sure that intake fans start low in the case and push from front to back and exhaust fans are high and pull warm air from front to the back.

Your equipment will produce heat, that's a given. The key is to stay within recommended levels.

As long as the temp inside your case is only a few 1-3C warmer than ambient temps than I can't imagine the number of fans making any real difference. The bigger difference will come from lowering your Ambient room temperature.

don256us said:

There are variables to cooling your machine. The old case may have been more efficient in moving air than the new case. 9 x 120 fans may not all be placed/pointed in the most optimal way. The temperature around the case (read room temperature) may be different from one temp reading to the next.

I like to use lots of slow moving fans that help each other out. The slow speed keeps noise to a very low minimum. By making sure that intake fans start low in the case and push from front to back and exhaust fans are high and pull warm air from front to the back.

Your equipment will produce heat, that's a given. The key is to stay within recommended levels.

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Yeah, I have the front, bottom and front-side panel all taking in air and the roof and rear exhausting it. Yeah, by now I've learned ambient temperature is the biggest variable, my brother has a desktop downstairs from my room and it only has about 4 fans and yet the temperature of everything is about 10C cooler than mine.

I'll bet downstairs is 10c cooler than upstairs too, right?

Blaylock said:

I'll bet downstairs is 10c cooler than upstairs too, right?

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It's a tad bit cooler down there, but I didn't any any idea it was THAT much cooler, lol.

What I still barely understand though is that adding a bunch of fans to a desktop that's in a warm ambient space doesn't seem to make a very big difference if anything for me... it's like the only way to really cool it at all is to move it to a cooler location.

That's right. More fans just equal more ambient air, not cooler air.

What you are noticing is called diminishing returns. For example, an average custom water cooling(let's say 2 fans and a 120.2 radiator as an example) loop will have a 10℃ delta between water temp and room temp. Double the radiator and fans you can get that to 5℃. Double them again and it only drops to 2.5℃. You will have gone from 2 fans and 120.2 to 8 fans and 120.8 and only see a 7.5℃ drop in temp. You can add a hundred 10k rpm fans to the loop and it will never get beyond the 10℃ delta of the original average loop.

Heatsinks work on the same principal. The closer to room temperature you keep your heatsink, the harder it is to get the next degree, no matter how big or how many fans you stuff on them.

Twisted4000 said:

This is going to be sort of a broad question, but there seems to be two sides of an argument: one says that the more fans and better cooling you have, the longer your system will last. Then there's this other side that says you only need what's necessary, because before any part of your computer will break down from being too hot for too long, you'll have probably replaced it or got a whole new system anyway.

Is an extra fan or two only really needed if your temperatures are TOO, or "dangerously" high, to the point that it will noticeably have problems or even overheat? Or does having an extra cool system do anything to actually improve your system?

I got this new case that supports up to 9x 120mm fans, more than my previous case, but my temps don't seem to be any better. Sometimes it seems as if having all these extra noisy fans aren't doing anything to actually cool down the system noticeably. Like, why have them there and produce all that extra noise? I dunno, is what I'm asking making any sense at all? It's sort of just a broad series of questions regarding PC cooling, what's necessary and what is too much.

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There is a point in which the law of diminishing returns sets in. Once you get to the point where the fan power is removing virtually all the warmed air from the case then adding more fans isn't really going to make any difference.

Alright got it. Thanks to everyone for all the replies, I can't believe I haven't thought that there's a point where the computer can't really get much cooler if it's in a certain spot.

Intake fans contribute to the heat load of a system, not only because of the fan motors but because they increase the average kinetic energy of the air molecules when they accelerate them -- and, from what I understand, the average kinetic energy of air molecules is the definition of temperature.

Magellan what the **** are you talking about? Are you suggesting that intake fans actually raise the temperature?

I personally think it's important to balance your number of intake and exhaust fans, and their airflow numbers.

If you only have one exhaust fan and no intake fans, it doesn't matter how much CFM that one fan pushes, you still likely won't have good temperatures for items inside the case. Cool air cannot be sucked into the case fast enough to replace the hot air that is being pushed out the back of the case. You'll have a vacuum. If you have three exhaust fans and one intake you have the same scenario (assuming the CFM of air pushed by the exhaust fans is greater than the CFM of the intake fan).

Having one intake fan and no exhaust fans is also bad. You end up with a bunch of hot air recirculating around in the case, because it cannot be exhausted from (or escape from) the inside of the case fast enough. It may be cool air coming in, but it just mixes with the hot air inside. If you have three intake fans and one exhaust you have the same scenario (assuming the CFM of air pushed by the intake fans is greater than the CFM of the exhaust fan). Some of the hot air will find it's way out of the case, but there will still be a lot left inside the case to recirculate. I once had a case that was in this scenario, it had four intake fans and one exhaust fan, and the temps were always a little high for the CPU, chipset, and graphics card. I saw a huge temperature drop when I upgraded that system to a more modern, better-designed case.

You might not be able to have your airflow perfectly balanced, but you want to at least try to get the intake and exhaust CFM numbers close.

The system I'm talking about:

Temps in old case:
CPU core temp: 35-40°C at idle, 50-53°C at load
CPU socket temp: 34-38°C
GPU: 40-45°C
HDD: 34-35°C
Northbridge chipset: 38-42°C
Four intake fans, one exhaust fan.

Temps in new case:
CPU core temp: 28-34°C at idle, 39-42°C at load
CPU socket temp: 26-30°C
GPU: 34-37°C
HDD: 27-29°C
Northbridge chipset: 32-35°C
Three intake fans, three exhaust fans.

Personally, I think one intake fan and one exhaust fan isn't enough to cool modern computers. I'd go with at least two intake fans and two exhaust fans (three of each would be even better), preferably in the 120mm to 140mm range with 60CFM or greater per fan. Also, 200mm fans are also good if they have decent airflow, most of them are rated at 100CFM or greater usually.

I went a little fan-crazy with my current main PC though, with six intake fans (rated at 300CFM for all combined in current configuration) and three exhaust fans (rated at 176CFM for all combined), but I still have good temperatures. So, I'm at 190CFM to the positive side of airflow. The actual airflow is probably lower, because I have restrictions like fan filters, cables, drive cages, and case fan grills in the way of the airflow, plus a water cooling radiator at the top exhaust. I chose quiet fans though, so I can hardly tell my computer is running most of the time.

Twisted4000 said:

This is going to be sort of a broad question, but there seems to be two sides of an argument: one says that the more fans and better cooling you have, the longer your system will last. Then there's this other side that says you only need what's necessary, because before any part of your computer will break down from being too hot for too long, you'll have probably replaced it or got a whole new system anyway.

Is an extra fan or two only really needed if your temperatures are TOO, or "dangerously" high, to the point that it will noticeably have problems or even overheat? Or does having an extra cool system do anything to actually improve your system?

I got this new case that supports up to 9x 120mm fans, more than my previous case, but my temps don't seem to be any better. Sometimes it seems as if having all these extra noisy fans aren't doing anything to actually cool down the system noticeably. Like, why have them there and produce all that extra noise? I dunno, is what I'm asking making any sense at all? It's sort of just a broad series of questions regarding PC cooling, what's necessary and what is too much.

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to me,
enough is enough.

I've once like the every most hot blooded soul on this planet; stuffed every slots and opening on my case with a fan.
not now. now, I'm more concerning about my air path.
adding more fans, only when I feel it's necessary.
such as when a component is blocking the air path.

but I still end up with 9 fans inside my case (10 if you include the PSU)

magellan said:

Intake fans contribute to the heat load of a system, not only because of the fan motors but because they increase the average kinetic energy of the air molecules when they accelerate them -- and, from what I understand, the average kinetic energy of air molecules is the definition of temperature.

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Never thought about that but technically speaking you would be correct. Is the increase significant? I would not think so unless you are talking about fans that far exceed the power and scale of what is used in a computer case.

I don't have any intake fans in my case, not one. I have two exhaust fans: a 120mmx38mm and a 60mm x 25mm, but the intakes for my video card and CPU side-draft heatsink are really close to filtered intake vents on the front and bottom of the case so they pretty much get ambient air as intake. It seems to work though, my overclocked GTX 780 rarely sees temps over 65 degrees celsius, while my o'clocked i7-3820 CPU has never gone over 75 degrees C.

I planned to put in a pair of 140mm x 38mm intake fans in the bottom of the case but never bothered.

Here's a basic guide to case cooling and how I setup and monitor the temperatures inside of case.

Case airflow and cooling is not hard to do but can be time consuming.
Setting up the case for optimum cooling is often the hardest and most time consuming part of a build... And often the most neglected.

• There is much more to cooling than good cases and good CPU / GPU coolers. Add the fact that many GPU's make more heat than CPU means getting that heat out of the case and keeping a cool airflow to components can be a challenge.
• There must be more air flowing through case than component fans are using. If the CPU cooler uses 70cfm and GPU uses 80cfm fans we need 180-220cfm.
• Cases, especially those with filters, usually benefit from fans with higher static pressure ratings than stock fans... "cooler" fans instead of "case" fans.
  Intakes are typically have more restricted than exhaust because of air filters, more restrictive grills, HDD cages, etc.
• I prefer more intake than exhaust. And don't confuse number of fans with amount of airflow... or airflow with airblow
  • airflow is flowing cool air from intake to component and flowing hot air from component out of case without the hot air mixing with the cool air.
  • airblow is lots of fans blowing air with some of hot air from components mixing with cool air making it warmer resulting in warm air not cooling components as well as the cool air will.
• Putting fans in case as intake and/or exhaust is only the first step. These fans only move air in and out of case.
• This does not mean heated air is not mixing with cool air.
• Nor does it mean cool air is going to where it is needed.
• Getting the air to flow inside of case properly is even more important. We still need to manage where the air flows inside the case. We can do this several ways; deflectors, more intake fans.. & exhaust fans, removing PCI slot covers, removing vent grills, removing HDD cage, using fans with higher pressure/airflow, building ducts to or from CPU/GPU cooler, etc.
• Using a remote temperature sensor to monitor what air temps are is the key to finding out where the cool air is flowing and knowing heated air is not mixing into it. By monitoring this we can than make changes to get airflow the way we want it.

How to monitor air temperature different places inside of case:

• A cheap indoor/outdoor thermometer with a piece of insulated wire and a plastic clothspin works great.
• Made up with floral wire and tape. We don't want anything to short out with metal.
  
• Clip and position sensor where I want to check the temp. Make it easy to see what the air temp going into components actually is relative to room temp.
• When system is working air temps going into coolers will be 2-3c warmer than room.. up to about 5c is okay.

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Feel free to ask questions after reading.