Is a rear case fan necessary with a CPU cooler?

ShellShock · 6 Jun 2023 at 08:20

I am thinking of ordering a Noctua NH-U12A CPU Cooler (120 mm) for my Fractal Design Define R6 Midi Tower Case. The rear fan on the cooler will be facing towards the rear grill on the case - I estimate probably 30-50 mms from it - and I think I will have the fan pushing air out of the rear grill.

My question is, should I fit a rear fan too, to the rear grill? Maybe a Noctua NF-A12x25 PWM Fan (120mm). Is it better to have a second fan also pushing air directly out the rear grill, or will it obstruct the fan on the cooler, as the two fans will be close to each other, side by side (both pushing air in the same direction, out the rear grill).

The cooler will be replacing a Corsair Hydro H80i V2 water cooler AIO, which is over 5 years old, and is now making a horrific noise at high RPMs (not sure if it is the pump or the fan). I am bit wary now of water coolers needing maintenance after a few yeas, and I want something that should be less hassle in the long term. Also I have no need for RGB (definitely prefer not to have it), which rules out a lot of AIOs now.

mickyflinn · 6 Jun 2023 at 09:50

A good rule of thumb is to have a gap one 3rd the size of the fan which would be 40mm for a 120mm fan.

Airflow is important so getting hot air out of the case faster will keep components cooler .

Water cooler the only real maintenance needed is cleaning the radiator for dust.

ShellShock · 6 Jun 2023 at 10:27

Thanks for your reply. I wavering over air or water coolers. I have been looking at the bequiet AIO water coolers, but the one thing putting me off (strangely) is they come with coolant top-up to use after a few years. Is that really necessary? It is the kind of thing I would forget.

mickyflinn · 6 Jun 2023 at 10:43

ShellShock said:
Thanks for your reply. I wavering over air or water coolers. I have been looking at the bequiet AIO water coolers, but the one thing putting me off (strangely) is they come with coolant top-up to use after a few years. Is that really necessary? It is the kind of thing I would forget.

It's actually a good thing to have a coolant top because air that's in the water (which develops over time) can be released and topped up..

What size aio ?

What CPU you cooling ?

ShellShock · 6 Jun 2023 at 13:33

I am thinking of a 240 AIO, preferably with minimal RGB (my case is not transparent anyway). I have got a 120 AIO now which is really noisy at over 1500 RPMs (getting worse).

CPU is Intel Core i9 9900K 3.60GHz Coffeelake CPU overclocked to 4.60GHz socket LGA1151.

SpellowHouse · 7 Jun 2023 at 05:41

ShellShock said:
I am thinking of ordering a Noctua NH-U12A CPU Cooler (120 mm) for my Fractal Design Define R6 Midi Tower Case. The rear fan on the cooler will be facing towards the rear grill on the case - I estimate probably 30-50 mms from it - and I think I will have the fan pushing air out of the rear grill.

My question is, should I fit a rear fan too, to the rear grill? Maybe a Noctua NF-A12x25 PWM Fan (120mm). Is it better to have a second fan also pushing air directly out the rear grill, or will it obstruct the fan on the cooler, as the two fans will be close to each other, side by side (both pushing air in the same direction, out the rear grill).

The cooler will be replacing a Corsair Hydro H80i V2 water cooler AIO, which is over 5 years old, and is now making a horrific noise at high RPMs (not sure if it is the pump or the fan). I am bit wary now of water coolers needing maintenance after a few yeas, and I want something that should be less hassle in the long term. Also I have no need for RGB (definitely prefer not to have it), which rules out a lot of AIOs now.

Well, it kinda depends on a number of factors.

Personally, I went the same way with coolers. AIO are fantastic, but the truth is they are less reliable and often much noisier than a Noctua. The water in them does evaporate over time, and this can lead to them being far less efficient. Also, the pump is a source of noise. Certainly, for current cooling requirements, you are better with a Noctua. (I use the Noctua NH-U12A chromax black, and other assorted coolers for lesser builds.).

Anyway. In general, a PC does not need fans on the back if it has fans on the front. Builders often put a fan on the back to ensure that air being pumped in to the case is going in the right direction, and clearing the warm air from the motherboard and CPU, rather than escaping from the bottom of the case, etc. But, since many builds have multiple fans on the front, this is often not an issue. I have two PCs that have two fans on the front and none on the back. They do not benefit from a fan on the back because with the particular cases they use, the air is not escaping anywhere else, it's all piling through the back vent, even without the help of a fan.

Cyber-Mav · 7 Jun 2023 at 11:34

My rule, if there is a space for a fan stick one in there

Armageus · 7 Jun 2023 at 11:47

If your case hasn't got a window (i.e. looks don't matter), then you could buy/construct a duct to fit between the cpu cooler fan and the rear outlet, to ensure the hot air can only go directly outwards

mickyflinn · 7 Jun 2023 at 11:47

ShellShock said:
I am thinking of a 240 AIO, preferably with minimal RGB (my case is not transparent anyway). I have got a 120 AIO now which is really noisy at over 1500 RPMs (getting worse).

CPU is Intel Core i9 9900K 3.60GHz Coffeelake CPU overclocked to 4.60GHz socket LGA1151.

Air cooling get the Thermalright Peerless Assassin 120 SE it's a beast for the money.

Thermalright Peerless Assassin 120 SE Review: Incredible, Affordable Air Cooling Performance

Shockingly cool and quiet, less than $40!

www.tomshardware.com

Mcnumpty2323 · 7 Jun 2023 at 12:23

ShellShock said:
Thanks for your reply. I wavering over air or water coolers. I have been looking at the bequiet AIO water coolers, but the one thing putting me off (strangely) is they come with coolant top-up to use after a few years. Is that really necessary? It is the kind of thing I would forget.

It's a good option to have yes
Over time you lose coolant due to permeation
Talking about years
But without the ability to top up
People end up throwing away AIO that still have
A perfectly good pump in there
Just because the air in there
May start making it noisier and cause some people
To assume the pumps gone faulty
I still have some old swiftech AIO units
Those were the first AIO I remember being able to top up
Not looked at the bequiet ones
But the swiftech ones could even be expanded to include a gpu

SpellowHouse · 8 Jun 2023 at 07:21

ShellShock said:
Thanks for your reply. I wavering over air or water coolers. I have been looking at the bequiet AIO water coolers, but the one thing putting me off (strangely) is they come with coolant top-up to use after a few years. Is that really necessary? It is the kind of thing I would forget.

Yes, it is necessary. They do lose water. Believe it or not, it does manage to permeate through the walls of the flexible tubes. It's a good idea to check the levels every two years.