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.