CPU fan in exhaust mode?

jonisvipr

jonisvipr

jonisvipr

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So I've recently finished my new rig and went from full-atx to mini-itx. The only concern I have with my build is that the fan of my Noctua NH-U12S CPU cooler does not have enough clearance from my corsair 2x16GB RAM on the motherboard. If I try to install the fan as an intake, it pushes the RAM to the side by an uncomfortable amount.

Due to this, I set the CPU fan as an exhaust to the back side of the cooler. However, it is very close to the back exhaust fan of the case. Not touching or anything, but they run at different RPMs. The CPU fan based on temps (560-900RPMs), and the back case fan is connected to the AIO pump connector and thus runs at 1400RPMs continuously.

My case is an NZXT H210 and the fan setup is 2 front intakes, 1 exhaust at the back and one exhaust at the top, with the CPU fan in exhaust mode blowing directly on the back case fan. Peak stress temps reach 74 degrees and idle 32, but I am still a bit concerned if I should switch to an AIO, or if an exhaust CPU fan so close to the case back exhaust fan is still suitable for cooling and I should leave the system as is.

Thanks for any advice.
 
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The Noctua NH-U12S is supposed to have 100% RAM clearance, so I am surprised to hear that it is pushing against your Corsair RAM modules.

What Motherboard are you using? Can you also post a picture of the setup? It sounds like you have the CPU cooler installed back to front, especially as you have space for two 25mm fans at the back (one on the cooler with the case fan right next to it).
 
@jonisvipr

I use the same cooler. It clears the RAM (mine are in 2 and 4), fine. Its height adjustable, so you could put the fans a little higher, but might look a little strange and not have quite as good airflow for the CPU??
 
@JClarke
I am using the ROG STRIX B560-I GAMING WIFI.
There is a wrong way with installing these CPU coolers? *shocked* Thought both sides have the same clearance but you might be right because I've checked the dimensions here: https://noctua.at/en/nh-u12s/specification and it does seems that one side has more clearance. This is strange as I was able to mount it without any issues and temps really don't look bad at all. Anyway, here is a pic as well. Will probably re-fit the cooler later today.
8zc7awh
https://imgur.com/a/8zc7awh

@Zeebedy
Only have 2 RAM slots, otherwise I would do a 2-4 setup. The fan can't come off high enough to clear the RAM without touching the case and it would also not look very nice. Will try to re-fit the cooler and see if that clears it or otherwise its an AIO or CPU fan in exhaust mode for this machine.
 
jonisvipr said:
@JClarke
I am using the ROG STRIX B560-I GAMING WIFI.
There is a wrong way with installing these CPU coolers? *shocked* Thought both sides have the same clearance but you might be right because I've checked the dimensions here: https://noctua.at/en/nh-u12s/specification and it does seems that one side has more clearance. This is strange as I was able to mount it without any issues and temps really don't look bad at all. Anyway, here is a pic as well. Will probably re-fit the cooler later today.
8zc7awh
https://imgur.com/a/8zc7awh

@Zeebedy
Only have 2 RAM slots, otherwise I would do a 2-4 setup. The fan can't come off high enough to clear the RAM without touching the case and it would also not look very nice. Will try to re-fit the cooler and see if that clears it or otherwise its an AIO or CPU fan in exhaust mode for this machine.
Click to expand...

Good point, I never considered the side panels :rolleyes:

FWIW I have the cooler base with the Noctua label on the top of the cooler, the text / logo facing to the right side, I dont think it matters but thats how I haev mine.
 
jonisvipr said:
@JClarke
I am using the ROG STRIX B560-I GAMING WIFI.
There is a wrong way with installing these CPU coolers? *shocked* Thought both sides have the same clearance but you might be right because I've checked the dimensions here: https://noctua.at/en/nh-u12s/specification and it does seems that one side has more clearance. This is strange as I was able to mount it without any issues and temps really don't look bad at all. Anyway, here is a pic as well. Will probably re-fit the cooler later today.
8zc7awh
https://imgur.com/a/8zc7awh
Click to expand...

Yeah, a slight difference in clearance that might make all the difference for you.

To be fair, the Noctua cooler is almost symmetrical. I have a Scythe Mugen 5 where there is a very clear orientation.

Fingers crossed everything fits after you re-mount it.
 
ROG STRIX B560-I is about 48-49mm center CPU to near side of RAM socket, same as NH-U12S is center base to front of fan. So if RAM is as thick or thicker than RAM socket fan won't fit on front of cooler.

Good news is fan works same pulling as pushing with possibly slightly higher noise level. This is because exhaust side of fan has more clearance from impeller to back of fan housing (because of motor mounting).

Pretty sdure NH-U12S is symmetrical with base is centered under fins.

I would remove rear exhaust fan and just let cooler fan push air out exhaust vent.
 
It won't make much difference, however fan blowing onto CPU will be more efficient. This is due to fans being a compressor, and the higher density air the fan outputs is better for cooling.
 
Fan flows the same on front of cooler as on back of cooler. Thus airflow around cooler and on to / off of CPU is also the same with fan on back as on front.
 
You could remove fue exhaust case fan as it would be all but pointless so close to the cpu fan and at different rpms.

Although saying that if the case fan is faster it shouldn't matter.
 
doyll said:
Fan flows the same on front of cooler as on back of cooler. Thus airflow around cooler and on to / off of CPU is also the same with fan on back as on front.
Click to expand...

A fan 'compresses' air, this higher density air is more efficient at cooling.

Having the fan on the exhaust side of the cooler, the benefit of compressed air is lost

Re air-flow this is not 100% the same, as a fan will draw air from the sides, meaning it will draw some air that's not going past the heat-sink immediately in front of it. You could get the air-flow the same if using some trunking between heatsink and fan.
 
So I flipped the cooler, and indeed it seems to give just a bit more clearance, BUT still not enough for these beefy sticks though, still barely, pushes it. I was able to first mount the cooler along with the fan, and then push the RAM stick in without any relative force. Still no horizontal space for the RAM stick though. Here are some pictures to give you an idea. Also, temps are lower by 2-3 degrees with this setup (max 72), nothing major but will still keep this setup probably until I put the AIO in, reason I didn't use the AIO from the beginning is because I will be travelling frequently with the case in my carry-on luggage and I don't want any fuss from airport security about the water in the AIO so had to resolve to this bulkiness.

https://imgur.com/a/Ng5KcVz
 
JasonM said:
A fan 'compresses' air, this higher density air is more efficient at cooling.

Having the fan on the exhaust side of the cooler, the benefit of compressed air is lost

Re air-flow this is not 100% the same, as a fan will draw air from the sides, meaning it will draw some air that's not going past the heat-sink immediately in front of it. You could get the air-flow the same if using some trunking between heatsink and fan.
Click to expand...
Fans "vacuum" air in at same rate they "compress" air out.

The difference between atmospheric pressure of air on your chest and what is on your feet is about 1.86mm H2O .. about twice what most fans make, even the best ones. And that is static pressure, meaning how much pressure fan can push in a sealed container .. hardly a situation we will ever use our fans at. Even if your fan is rated 1.86mm H2O, if you have 0.93mm H2O of resistance resulting airflow will be almost nonexistant.
 
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