Question about liquid CPU coolers

Netherspark

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I might try a liquid CPU cooler instead of the air coolers I've always used, but I have a quesiton about placement of the radiator/fan:

Most of the setups I've seen have the radiator/fan taking the place of the main exhaust fan on the back of the case (sometimes the only case exhaust). Isn't this a bad idea? The fan would generally be controlled by the CPU fan header, so the speed would be determined by the CPU temperature instead of the system or case temperature.

If the cooler is doing its job and keeping the CPU temp down, then the fan speed would be low, possibly too low to be properly keeping the case cool. Seems to me it would be better to keep the CPU fan and exhaust fan separate.

Does this matter at all?
 
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mrjack2207

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In my experience the radiator fans tend to spin faster than normal case fans anyway. However it doesnt really have a negative impact. If you want to see something crazy, people have their radiator as a intake at the front of their case, causing it suck hot air from the cpu into the case, heating everything up !

 
Yes, you are right — putting a liquid cooler fan as exhaust on the back replacing the case exhaust fan is a very bad idea, as far as I have seen. Mostly now, builders put the radiator fans either on the front of the case or the top (as intake). Having a side/bottom fan as exhaust would be great for case's airflow.
 

JalYt_Justin

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I have my radiator mounted this way, and I'll be the first to tell you that it makes basically no difference. Front intake placement is fine, back exhaust placement is also fine (in some instances). Putting a radiator in the front does not heat up all of your other components as much as you think, and case temperatures generally don't fluctuate much at all unless you have truly horrible case airflow, generally caused either by intrusions or having literally no fans at all.

EDIT: I believe JayzTwoCents did a video on this explaining it pretty well. Radiator placement only affects the airflow in and out of the case by maybe a few degrees - not enough to warrant changing your radiator's position unless you're already near the point of overheating. In which case, you've got more problems than your radiator's placement.
 

mrjack2207

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I don't agree with the radiator as being a intake at all, i feel that the best set up is to have a radiator at the top of the case with a rear exhaust as well

 

Netherspark

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I actually considered doing that. I have a mount for a front fan directly in line with the rear fan, so would have the radiator on the top front position, with the radiator fan sending the hot air straight accross to the exhaust fan. Would that be a bad idea?
 

Eximo

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For absolute best component temperatures, that is actually advisable. And the installation guides for most larger radiators show placing it in the front. Delta temperature is important, and even decently warm air coming off a radiator is still cooler than your typical running PC component.

When it comes to blocking exhaust fans you have to consider what is producing heat in the computer in the first place. With an all in one you are moving the vast majority of the heat to the radiator which is pulling in the sightly warmed case air. Ideally any case with only an all-in-one as exhaust needs at least one intake fan to pull in cool air.

If you have an axial cooled GPU, and only have a CPU all-in-one as exhaust, that is probably worst case scenario for CPU temperatures. If you have a standard blower style GPU, then it also is pulling air out of the case and exhausting it. Again you need decent air flowing into the case to prevent overheating.

In a typical old school case you had a more bizarre situation where the the PSU, mounted up top, was drawing in all the warm air. Power supplies become less efficient with heat, but in many computers it was the only exhaust fan. Also made tower computers top heavy, which was never a good idea.

In a typical contemporary inexpensive case the power supplies are typically mounted in the bottom and have a closed loop of drawing in outside air and immediately exhausting.

In a higher end case, there are usually more exhaust ports on the top of the case. So having a rear mounted radiator, or top mounted, is less of a concern.

Short answer: it depends.
 
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Eximo

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As long as you have air moving across the CPU VRMs (the circuitry surrounding the CPU) everything should be fine. That is the only downside to the majority of All-In-Ones, reduced airflow across the power circuitry.

 

mrjack2207

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Well I've got a 220mm front intake, 240mm side intake, 140mm rear exhaust and 2x120mm exhaust on the radiator, in my experience this set up seems to work great.

 
There are pros and cons on radiator placement.
It depends on what you are tying to accomplish.

What are YOU trying to accomplish?
Do you care about noise?
What is your case?
What parts are going inside?
Will you be overclocking? If so, modestly, or maximally?

My guess is that a radiator set up to exhaust air is better on balance.
Not so good for max cpu cooling, but better for graphics and motherboard.
 


Placing the radiator is giving you only two options: Either placing it as intake (letting the air from outside cool the radiator — heating up what's inside the case a few more degrees, in the expense of keeping your CPU in check); or placing it as exhaust (letting the already warm air from inside the case cool the radiator — damaging the radiator in the long run, in the expense of keeping everything else inside the case cool). Of course, this is negligible, if both the liquid cooler and the case's airflow are good.