H150i CFM Confusion

Hi all

I'm a bit confused as to the correct CFM of the iCUE H150i Pro XT.

The official product page says max airflow 75 CFM. However it comes with 3 x ML120 fans which are also 75CFM each according to its product page .

Does this mean that the overall CFM of the H150i Pro with 3 x ML120s is capped at 75CFM and therefore each fan only running at a third of their capacity?....OR is the total max airflow 3 x 75CFM = 225 CFM?

I did email corsair and they said its capped at 75CFM which didn't seem to make sense to me so wanted to double check here what the deal is from those who have experience with this model.

Any help much appreciated as I'm trying to work out how to balance my airflow!

Thanks

Each ML120 fan theoretically produces 75 cfm in free air (not on the radiator) at the 2400 rpm maximum speed. The fans are not stacked and airflow is not additive even if they were. If you are making comparisons to other fans, you do it one a 1:1 basis at the fan level.

As for "balancing your airflow" it counts as 3 fans, but getting the actual cfm from real use is going to be a guess. You are not going to be running them at 2400 rpm. The speed will change and the radiator drastically reduces the actual airflow. It varies with fan geometry, but you can make a ballpark estimate that each fan delivers half of its maximum possible airflow when restricted by the radiator.

Basically, once you mount them on a radiator, with a dust filter up front and a more or less restrictive case, you can take the airflow figures and toss em down the drain.

For a radiator fan anyway, it is really static pressure you should be looking at. High airflow fans with steep blade angles have airflow specs that put a ML fan to shame, but they are worthless trying to push air through fins and filters.

Thanks for the replies both. Very helpful. If possible would you be able to give me your opinion on this cooling layout I'm planning on? (Image attached)

i.e would it provide sufficient cooling and will I be able to balance the airflow ok with this layout? I will be using a 2080ti and 9900k - pretty hot components so want to make sure I'm using the best possible cooling setup with the fans I have.

(Admittedly I bought these fans assuming the H150i XT was 225CFM in total not realising that it's actually realistically 75CFM in total.)

Thanks for any advice again

In an O11D/XL you will likely get the most efficient cooling by putting the radiator in the side vertical placement as intake. You can use it up top as well, but you will be exhausting the GPU waste heat through the radiator. This elevates the baseline coolant/CPU temp higher than it normally would be.

Some cases are a real pain with their glass panels. The O11 is not. Mine runs with 9 exhaust fans and no intake, end glass panel off half the time. There isn't a dust layer forming and both my XL and D were some of the least dust magnetic cases I have owned and both ran full exhaust. You don't need to overthink this one. You can put the radiator in the side and still use the rear panel dust filter without choking the life out of it. The bottom filter and assembly in general is a bit more restrictive, but this still leaves you good airflow without having to blast the fans.

9 exhausts and no intake?! Wow didn't realise that was ok to do! :bigeyes:

OK I see, thanks for the reassurance and advice. I've attached the updated layout (just swapped the top and side)

If you would allow me one more overthinking question:

I actually did originally plan to have the AIO as a side intake like you suggested, but there's been a lot of recent talk about tubes up side/front mounts being bad because of air bubbles which persuaded me against it. (GN did a very popular vid about it that you've probably already seen?)

Is a side intake still advisable even if I can only mount it with tubes up?

Thanks for the continuous tips!

Yes, I have seen the tubes up "demonstration" as well the Linus Tech "dust ball" vid that sent untold numbers of people into these positive pressure calculations. If you listen carefully to the GN video, he says it might cause some noise with tubes up. All the doom and gloom was for the having the radiator below the CPU block and pump, which is a genuine problem. People have been running their AIOs with the tubes up for a long time. It doesn't lead the cooler to a premature end.

Regardless of what you decide, switching the radiator from top to side or vice versa after building is not major surgery. You can start anyway you like and see how things go. The only inadvisable set up with the O11 is side exhaust. The position of the fans relative to the small side glass kills the airflow to them. It's easier for air to go in any other direction and they become very limited in their ability. This is why my side glass comes off quite a bit. Most people are going to prefer to keep it on and thus the need to run them as intake.

All fan exhaust is a more common full water system set-up and a product of having 3x360mm radiators. If I only had 2x360, then some fans would be intake. This is not something you would want to do with an air cooled GPU.

I see, yes I hear you about the tubes..the highest point in the system won't be the pump so wouldn't be that detrimental.

Great, I'm excited to get building, thanks loads for your time and advice, it's very much appreciated, I'll let you know how I get on!