[SOLVED] High CFM fan too close to CPU fan - best option?

[TradeJack01]

Hi All,

I have a server board in a PC case.

The CPU has one heatsink with two fans blowing front to back:
https://noctua.at/en/nh-u9dx-i4

My case fans:
https://www.ebay.com/itm/274834492168

One case fan will be mounted to blow directly at the CPU at a close distance (7.5CM). When the case fan blows at speed, the Noctua fans are unable to slow down.

Is there any harm in this setup? When the system runs hot, the case fan will blow massive amounts of air at the CPU fans. Will they be over-spun? Any harm in that?

Should I un-power or remove either of the CPU fans instead?

Thanks!

 

[Lafong]

You should be able to get a good handle on the options with an hour or 2 of experimentation.....trial and error.

Don't know your case or case fan setup, but that's not really necessary as you should rely on trial and error regardless.

I can't recall any fan orientation actually "harming" anything assuming temps remain acceptable.

I'd likely start with leaving the Noctua setup as is...2 fans, both blowing to the rear.

Presumably you have an exhaust fan at the back.

Try a single intake fan at the front, generally blowing toward the Noctua, so that general airflow is front to rear

One exhaust at the back.

Evaluate temps with that setup as a baseline.

If temps unacceptable, try 2 front intakes if you have a second mounting point on the front.

Any fan mounts on the top or sides of the case may not be worth using at all.

Make sure you know which direction each individual fan is moving air.......you don't want an intake blowing out or an exhaust blowing in...for instance.

You can spend as much time as you care to in experimentation. How much time you spend may be driven by your anxiety level re temps. Some will accept X degrees. Others want to get X minus 5 for whatever reason......good or bad.

 

[Zerk2012]

Hi All,

I have a server board in a PC case.

The CPU has one heatsink with two fans blowing front to back:
https://noctua.at/en/nh-u9dx-i4

My case fans:
https://www.ebay.com/itm/274834492168

One case fan will be mounted to blow directly at the CPU at a close distance (7.5CM). When the case fan blows at speed, the Noctua fans are unable to slow down.

Is there any harm in this setup? When the system runs hot, the case fan will blow massive amounts of air at the CPU fans. Will they be over-spun? Any harm in that?

Should I un-power or remove either of the CPU fans instead?

Thanks!

If the case fan as you call it is in direct line with the CPU cooler then that is not a good thing you have the lower CFM fans blowing one way into the cooler and the case fan higher CFM blowing directly against it.

EDIT all airflow should be in one direction not 2 fighting against each other.

 

[TradeJack01]

You should be able to get a good handle on the options with an hour or 2 of experimentation.....trial and error.

Don't know your case or case fan setup, but that's not really necessary as you should rely on trial and error regardless.

I can't recall any fan orientation actually "harming" anything assuming temps remain acceptable.

I'd likely start with leaving the Noctua setup as is...2 fans, both blowing to the rear.

Presumably you have an exhaust fan at the back.

Try a single intake fan at the front, generally blowing toward the Noctua, so that general airflow is front to rear

One exhaust at the back.

Evaluate temps with that setup as a baseline.

If temps unacceptable, try 2 front intakes if you have a second mounting point on the front.

Any fan mounts on the top or sides of the case may not be worth using at all.

Make sure you know which direction each individual fan is moving air.......you don't want an intake blowing out or an exhaust blowing in...for instance.

You can spend as much time as you care to in experimentation. How much time you spend may be driven by your anxiety level re temps. Some will accept X degrees. Others want to get X minus 5 for whatever reason......good or bad.

I am not anxious much about temperatures.

Air from the front case fan is blowing like crazy. If I removed both CPU fans CPU would still not go over 55degrees just from the front fan blowing at the heatsink. And yes, there will be a rear fan later.

I am a little worried about damaging the front CPU fan by high airflow going into it and over-spinning the RPM.

 

[TradeJack01]

Not enough information the case link just goes to a fan. If the case fan as you call it is in direct line with the CPU cooler then that is not a good thing you have the lower CFM fans blowing one way into the cooler and the case fan higher CFM blowing directly against it.

I am not sure how to post a photo without finding somewhere to host it. What additional information would be helpful? And you are right, they are in direct-line. The very high CFM case fan is blowing into a lower CFM Noctua CPU fan at a close distance.

You mentioned the setup is not a good thing. Why do you say that? Which aspect? I am worried about damaging the CPU fan. Cooling seems to be excellent since there is huge airflow.

 

[Zerk2012]

I am not anxious much about temperatures.

Air from the front case fan is blowing like crazy. If I removed both CPU fans CPU would still not go over 55degrees just from the front fan blowing at the heatsink. And yes, there will be a rear fan later.

I am a little worried about damaging the front CPU fan by high airflow going into it and over-spinning the RPM.

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[Lafong]

I am a little worried about damaging the front CPU fan by high airflow going into it and over-spinning the RPM.

Never heard of such a thing.

You can easily monitor any fans speeds.

If highly concerned, get a slower intake fan or remove it entirely as temps so far seem to be OK.

Or move the intake to the exhaust side so nothing is blowing on the CPU cooler.

The PC is apparently generating little heat and the Noctua is doing its normal good job.

 

[Zerk2012]

Air should enter one direction and exit the other blowing the CPU cooler air toward a higher CFM fan going in the other direction don't make sense, you can always switch the direction of either the cooler fans or the case fan to work together instead of against each other.

 

[TradeJack01]

 

[TradeJack01]

Air should enter one direction and exit the other blowing the CPU cooler air toward a higher CFM fan going in the other direction don't make sense, you can always switch the direction of either the cooler fans or the case fan to work together instead of against each other.

Air is all blowing in one direction, front to back.

 

[Lafong]

What are temps with the front intake totally removed?

What are temps if the front intake is moved to the exhaust side?

What are temps if the front Noctua fan is removed entirely?

Either should remove your anxiety and you have no signs of high temps.

 

[TradeJack01]

Temperatures are 51ish with two CPU fans and one front intake fan.

Temperatures are 52 with the back CPU fan and front case fan.

The temperature is 54 with just the two CPU fans, no front case fan.

 

[Lafong]

Take the path of least worry.

None of those temps are significant.

The front fan appears to be doing very little to reduce temps and likely adds to noise. What's the point?

 

[TradeJack01]

I want to cool the motherboard and DIMMs next to the CPU as well, as well as blow air length-wise across the motherboard all the way to the back.

 

[Lafong]

I want to cool the motherboard and DIMMs next to the CPU as well, as well as blow air length-wise across the motherboard all the way to the back.

Then do what you must.

You'll have to decide priorities............like a surgeon in an emergency room at a hospital.

You'll have to take into consideration: the case, case fan mounting points, available fans, tolerance for noise, tolerance for a given temperature, indifference to expense, indifference to time spent, willingness to accept random events beyond your control, etc.

At autopsy after the PC drops dead, there's a very good chance you'll never know whether your decisions extended or reduced life expectancy.

 

[TradeJack01]

Agreed, yes just a little worried about wearing out (through over-spinning) my two little Noctua CPU fans. Maybe I will just completely remove them or move them out of the way of the case fan, or at least one of them. Then I can keep that one as a spare for when/if the other one dies.

 

[Lafong]

Replacement fans for that Noctua are 20 dollars.

You could of course use any fan anywhere you can mount it, even with Velcro or twist ties if need be.

I guess your case mounts are 120 mm. The Noctuas are 92mm

Noctuas are highly durable. I've got 6 years on one right now with zero issues.

Quietest method without buying new stuff would likely be put that 120 mm on the exhaust side. Nothing in front. Pull the back fan off the Noctua and keep it for a spare.

Maybe you don't care about noise.

Or keep the 120 intake where it is never mind the noise, if that helps to cool whatever else you are worried about....RAM, VRM, whatever. Remove a Noctua from the cooler if you want as the second fan on a Noctua typically helps only 2 or 3 degrees. You don't seem to be in temp danger zone.

Or do yourself a favor and buy a Noctua NF-F12 120mm for the front intake for about 25 dollars and throw the current Delta fans in the trash.

Lots of choices. Sort it out however you want based on personal comfort level.