Question AIO and case compatibility check ?

Aug 20, 2025
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Hey, im new here.

I was wondering if the case and AIO I am currently eyeing up for my new build are compatible?

Case is the Fractal Define 7
AIO is the ARCTIC Liquid Freezer III Pro 420

I am sold on the case, always loved the Define series, but I am seeing different info on the
size of AIO you can cram in the top. Some sites say 420 and some say 360, it would probably be a tight fit for not that much more cooling but for some reason I have set my eyes on the 420 one.
So, anyone with experience who can advise me?
 
The problem with arctic coolers and the reason they tend to work better than other similar coolers is the rad is thicker.

The other dimensions are the same as any other radiator of similar size. The all use fairly standard mounting methods and holes. If the case says you can put a 420 rad in the top it means it will fit.

What you seldom find in the specs is how much clearance there is between the top of the case and where the motherboard mounts. What will fit also depends on the motherboard. Some motherboard have massive heatsinks on that side of the board that might contact the radiator.

Really consider air cooling again. There are only very rare cases where you have a technical need for water cooling. If it is all for appearance rather than function then that is a personal choice.
 
The problem with arctic coolers and the reason they tend to work better than other similar coolers is the rad is thicker.

The other dimensions are the same as any other radiator of similar size. The all use fairly standard mounting methods and holes. If the case says you can put a 420 rad in the top it means it will fit.

What you seldom find in the specs is how much clearance there is between the top of the case and where the motherboard mounts. What will fit also depends on the motherboard. Some motherboard have massive heatsinks on that side of the board that might contact the radiator.

Really consider air cooling again. There are only very rare cases where you have a technical need for water cooling. If it is all for appearance rather than function then that is a personal choice.
Thank you for your reply and clear advice, I have considered air cooling (was going to pick one of Noctuas bigger ones at first). But then I thought about it and I came to the conclusion that I want to OC some. And my apartment is very small so I really want to try and keep temps down, my current pc has inadaquate cooling and i can really feel it. So even tho an air Cooler would do the job I just feel like I want to overkill the cooling as much as possible and the Arctic ones are aparantly very good and priced well too.
I did order the case after I made the post just so I can measure beforehand, and I know its not optimal for heat but I have no problem having the front door open during longer and heavier use.
I will take your advice and probably settle on a motherboard to order and meassure before i choose between 360 and 420. From my understanding the 360 should easily fit and will be very good.
 
The 360 may also not fit. It all depends on how much it overhangs the motherboard and how high the motherboard parts are.

If the 420 for example takes up the entire width of the case and it also extends beyond where the edge of the motherboard mounts then no motherboard will fit. A 360 will have a small gap between the cooler and the far edge of the case . It all depends on if the cooler overlaps the motherboard and then if there is clearance above the motherboard. You also have to worry about silly things like you can't fit you hands in to plug the 12 volt power cable that tend to plug into motherboards on that side. So the motherboard itself might under the cooler but you have no way plug in the cables. Also depends on if you can install the radiator after you install the motherboard. I have not seen details on that case. If you can completely remove the top of the case attach the radiator and then remount it with the motherboard already installed it would give you the best chance of success.
 
The 360 may also not fit. It all depends on how much it overhangs the motherboard and how high the motherboard parts are.

If the 420 for example takes up the entire width of the case and it also extends beyond where the edge of the motherboard mounts then no motherboard will fit. A 360 will have a small gap between the cooler and the far edge of the case . It all depends on if the cooler overlaps the motherboard and then if there is clearance above the motherboard. You also have to worry about silly things like you can't fit you hands in to plug the 12 volt power cable that tend to plug into motherboards on that side. So the motherboard itself might under the cooler but you have no way plug in the cables. Also depends on if you can install the radiator after you install the motherboard. I have not seen details on that case. If you can completely remove the top of the case attach the radiator and then remount it with the motherboard already installed it would give you the best chance of success.
Yeah, fortunatly you can completley remove the top on the define 7 so it should not be a problem, should is a powerful word here. Its also has mounting where you can slide the rad and not fixed points so a 360 should be able to clear the heatsink issue that you mentioned earlier. Im gonna try to measure as best I can when I have the case and a motherboard. I really have somehow set my eyes on the 420 one but I dont think it will fit with said motherboard heatsink issue like you mentioned. Its a pretty long case but 420 rads are big.
 
What is your intended processor?
Modern processors are binned and those capable of overclocking are used in better processors that sell for more.
Overclocking is not likely to be as good as the normal turbo mechanism for gaming.

Your case has not the best airflow capability.
The front side vents are not as good as a mesh front.
Liquid cooling is not magically better than air cooling.
The difference is where the heat exchange takes place.

All pc generated heat will heat up your apartment, regardless of the type of cooler.
The best you can do is to open a window to let heat escape.
 
What is your intended processor?
Modern processors are binned and those capable of overclocking are used in better processors that sell for more.
Overclocking is not likely to be as good as the normal turbo mechanism for gaming.

Your case has not the best airflow capability.
The front side vents are not as good as a mesh front.
Liquid cooling is not magically better than air cooling.
The difference is where the heat exchange takes place.

All pc generated heat will heat up your apartment, regardless of the type of cooler.
The best you can do is to open a window to let heat escape.
Im not sure on the processor yet, still researching. And if the normal turbo turns out to be better im fine with that.
And as I said I know the define 7 is not great for airflow but i dont mind keeping the door open for heavy use and I like to support my fellow Swedes, and I happen to love the look of it.
Of course liquid is not magically better, from what ive seen tho from watching benchmarks, reviews and videos over the years, if used properly it has an advantage.
I was looking at air at first and then I switched when I saw a good deal on a Corsair 360. But then I saw benchmarks for Arctic and it outperforms the competition at a much lower cost, probably because of the thicker rad as mentioned. And yes, all heat would end up inside the apartment and I do open my balcony when it gets unbearable. Im just saying that id prefer a lower temp overall, and Arctic seems to be in a really great spot. Unless you have some other solution with tests? Im still open to change.
 
Can you say what class of processors are you considering?
Top of the line $600 R9-9900X3d or Ultra 9-285K
Perhaps $250 class like R7-5700X3d or ultra 5 245K
Even the hottest 9900X3d can be handled with a Noctua NH-D15S:
https://ncc.noctua.at/cpus/model/AMD-Ryzen-9-9900X3D-1863

You should also know that aio coolers do not last forever.
In time, the mechanical pump will fail or get clogged.
Air will intrude through the tubes and the unit must be replaced.
Think of an AIO as a 5 year rental.

If heat in the apartment is an issue, the ultra processors are very heat efficient.
Any of them can be cooled with less than a top air cooler.