Cooling configuration question in the 750D

Hey, I'm building a new gaming rig using an Obsidian 750D, and have read heaps in the last few days, but still can't decide on how to cool my system. From what I've gathered, using a H110 mounted to the top as a pull/exhaust fan is the best option, although there has been a lot of good argument for using the H110 as intake to bring cool air over the radiator and into the 750D, despite raising overall case temp and possibly creating a dead zone by pulling cool air down when it should naturally exhaust warm case air up.

However, I was also considering using 2 H90's, both as pull/exhaust, one for the CPU and one for the video card GPU, and mounted next to each other at the top. Would this work, and if so, would the be more or less effective for the overall case temp and airflow? I'm more concerned about temp/airflow/dust rather than boosting OC performance.

Also, because I will be using 1 or 2 2.5" SSD drives for storage and mounting them on the back-side of the case (using the 4 tool-less drive slots), I will be removing the 2 internal 3.5"/2.5" drive cages to hopefully provide better airflow from the front fans into the case

My rig (without the coolers) so far:

MSI Z97 Gaming 9 AC

Intel S1150 Core i7 4790K

16GB (2x8G) Corsair 1600MHz Vengeance PRO

NVIDIA MSI GTX 980 GAMING 4G OC

Samsung 2.5" 850 EVO 500GB

LG BH16NS40 16x SATA Blu-Ray Writer

Corsair AX860

Corsair Obsidian 750D

I can't actually run any tests as I haven't got all the parts for the rig yet, but I would like to get a better understanding before I make any more purchases.

I think the place to start is with push exhaust on the roof. While the mounting requires an extra 8 screws, push usually gives you a small 2-4C improvement, and is often a quieter sound than pull. Exhaust in the roof generally makes things easier on total system flow. The only reason to turn the fans on the roof to intake is if you are getting really close to the edge of your thermal comfort zone. In theory, it allows "cooler fresh air" to pass through the radiator. However, where the PC is located in the room then becomes key to whether this is really true. If you have your case under a desk, that fresh air above the case isn't so fresh and is warmed by the ambient case heat. Same thing for any other restrictive space. Additionally, it creates an issue of how to exhaust all the air inside the case. Your one rear exhaust won't be able to keep up with 4 140's bringing air into the case. It doesn't look like the 750 is ventilated much in the back, and that means air will start to work against the fans. It's much harder to deal with the roof as intake unless you have good cause.

I haven't seen much data on H90's and 4790k. It should do the job unless you are going for a high overclock and/or live in a warm climate without AC. Whether or not to put both on the roof or one in the rear slot is an interesting decision. I would be tempted to try them both on the roof if the hoses will reach from the GPU.

I think the place to start is with push exhaust on the roof. While the mounting requires an extra 8 screws, push usually gives you a small 2-4C improvement, and is often a quieter sound than pull. Exhaust in the roof generally makes things easier on total system flow. The only reason to turn the fans on the roof to intake is if you are getting really close to the edge of your thermal comfort zone. In theory, it allows "cooler fresh air" to pass through the radiator. However, where the PC is located in the room then becomes key to whether this is really true. If you have your case under a desk, that fresh air above the case isn't so fresh and is warmed by the ambient case heat. Same thing for any other restrictive space. Additionally, it creates an issue of how to exhaust all the air inside the case. Your one rear exhaust won't be able to keep up with 4 140's bringing air into the case. It doesn't look like the 750 is ventilated much in the back, and that means air will start to work against the fans. It's much harder to deal with the roof as intake unless you have good cause.

 

I haven't seen much data on H90's and 4790k. It should do the job unless you are going for a high overclock and/or live in a warm climate without AC. Whether or not to put both on the roof or one in the rear slot is an interesting decision. I would be tempted to try them both on the roof if the hoses will reach from the GPU.

Thanks for the fast reply! Any particular reason for using push over pull for roof exhaust aside from noise? I thought push also meant having to clean dust between the radiator and fans much more often? And pull/ exhaust being an easy to clean exhaust? Id rather have less dust buildup than less fan noise.

I think the dust question will come down to other factors, mostly environmental. A case on the floor will pick up more dust than one on a 4 ft pedestal, whether or not you go push or pull. I understand the argument, but any dust in your radiator will be there because it naturally settles there when your PC is off or is already inside the case from your intakes. Push vs pull won't change that. A positive pressure system is your better bet for minimizing dust build up.

Serious testing usually give a small edge to push. Other factors could influence the decision, like flow from adjacent fans, obstructions, or hoses, but I find sound to be the most influential factor. When you mount in pull, you are putting the fan blades very close to the radiator. This often creates a higher pitched frequency in your fan sound. Most people are more sensitive to the higher wavelengths. All the "tech" with your fan's vanes on the outflow side is supposedly designed to minimize noise, straighten air, etc. etc. You are bypassing most of those features in pull. It is a relative simply thing to try it both ways. You can always change your mind later and your case is big enough to take the rad down and switch the fans without major difficulties.

On a side note, if you decide to run a different set of fans on the rad, regardless of push or pull you need to research before you buy. A lot of 140mm fans, particularly ones with hydro-dynamic bearings (or similar marketing name), will vibrate when exhausting air skyward. Check the consumer reviews before buying. Someone usually chimes in with that information.

Ah that makes total sense. I am planning to have my PC on my desk, about 2-3 feet off the ground. I think I will try pushing exhaust up through rad and out of the case like you have suggested, and give it a few months and see what the dust is like. If it's a mess I will try pulling exhaust and leave that for a while. Thank you so much for your help so far.

I know corsair reccomends the h110 to be set as intake, but has anyone actually had any benefit from this? Seems to me as everyone is opting against corsair and using it as exhaust when top mounted. Just curious...

Also worth noting that I live in Australia and do not have air conditioning, so high room temps and dust are more of a factor for me.

Here's a quick [ame=https://www.youtube.com/watch?v=UyC3lZ5WFMk]video[/ame] that explains why pull configuration is better. It also doesn't affect temperatures, which has been proved on many occasions.

I would say mount the H110 to the top as an exhaust, in pull. That way you get the hot air straight out the case and you can clean it easy. That's what I'm going to be doing when I get my 750D and the H110i GT (when it's available again).

Here's a quick

that explains why pull configuration is better. It also doesn't affect temperatures, which has been proved on many occasions.

 

I would say mount the H110 to the top as an exhaust, in pull. That way you get the hot air straight out the case and you can clean it easy. That's what I'm going to be doing when I get my 750D and the H110i GT (when it's available again).

This video was one of the original reasons I wanted to go for a pull config. I liked the idea of having the fans under the case roof but above the rad, pulling air from the case, through the rad, and out the top. But this is now going against the push/exhaust argument that we were just discussing above... This really isnt an easy decision hahaha

Look, I don't have anything against Linus. He oversimplifies things for a reason and that is beneficial to a lot of people. That said, the bit at the end about the dust is the dumbest thing I've ever heard. He's not stating "you don't get dust when in pull". He's only saying it's easier to clean because I can just wipe of the outside of the radiator, and I have an issue with that. The dust doesn't stop at the edge of radiator so you can wipe if off nice and easy. There is no filter. It gets deep in between the fins - push or pull. If you want to keep dust out, keep the case off the floor and a better video is Linus' own positive vs negative pressure. All that dust on his radiator (if real) wasn't conjured inside the fan. It came from inside his case. You can work out the rest. The beginning of the video concerning the push/pull craze is a little more worthwhile.

More seriously, he again oversimplifies push vs pull as the same. He later partially corrects and says "within the margin of error" which remains unstated and undefined. As I said, the difference is small and I wouldn't change for a 2-3C difference on a lab bench unless I was near my limit. The better is reason is sound quality and most radiator intended fans were designed to run as push.

It is definitely easier to mount the entire assembly as pull. You can run your 1.5 inch screws straight down through the case flanges, fans, and then into the rad. You'll need to get your own screws anyway. Start that way if you are more comfortable. If there is no irritating noise and everything else is fine, keep running that way. It's also fan dependent. I have some fans I would never run in pull on a rad. The noise is dramatic. Others you have to really listen for it. So feel free to experiment knowing you will not adversely affect your temps (or your dust) either way. It's silly to chase 2 or 3 degrees in performance at the expense of something you value more -- like convenience, sound quality, or you may prefer the look of the black rad on the roof.

Look, I don't have anything against Linus. He oversimplifies things for a reason and that is beneficial to a lot of people. That said, the bit at the end about the dust is the dumbest thing I've ever heard. He's not stating "you don't get dust when in pull". He's only saying it's easier to clean because I can just wipe of the outside of the radiator, and I have an issue with that. The dust doesn't stop at the edge of radiator so you can wipe if off nice and easy. There is no filter. It gets deep in between the fins - push or pull. If you want to keep dust out, keep the case off the floor and a better video is Linus' own positive vs negative pressure. All that dust on his radiator (if real) wasn't conjured inside the fan. It came from inside his case. You can work out the rest. The beginning of the video concerning the push/pull craze is a little more worthwhile.

 

More seriously, he again oversimplifies push vs pull as the same. He later partially corrects and says "within the margin of error" which remains unstated and undefined. As I said, the difference is small and I wouldn't change for a 2-3C difference on a lab bench unless I was near my limit. The better is reason is sound quality and most radiator intended fans were designed to run as push.

 

It is definitely easier to mount the entire assembly as pull. You can run your 1.5 inch screws straight down through the case flanges, fans, and then into the rad. You'll need to get your own screws anyway. Start that way if you are more comfortable. If there is no irritating noise and everything else is fine, keep running that way. It's also fan dependent. I have some fans I would never run in pull on a rad. The noise is dramatic. Others you have to really listen for it. So feel free to experiment knowing you will not adversely affect your temps (or your dust) either way. It's silly to chase 2 or 3 degrees in performance at the expense of something you value more -- like convenience, sound quality, or you may prefer the look of the black rad on the roof.

This clears up so much for me. Thankyou once again c-attack, you really seem to know what you are talking about here. Good to have a second perspective on the Linus video, as everyone else takes it as gospel truth. Given all that you have mentioned, it looks like I'm favoring pushing warm case air through rad and out top as exhaust once again. So long as the dust matanence is managable, it seems to be the best option.

For future reference, you mention that some fans you would never run in pull on a rad, while others you'd really need to listen for. What makes a good rad pull fan? Larger pressure/bigger blades or having more distance betweem the blades and the radiator? BTW sorry if I am re-hashing and asking stuff that has been covered in previous topics, I'm just a little new to serious rig building and need the re-assurance that I know what I am doing XD

Cheers guys. Ive decided to start by going push/exhaust for now, and just look at it in 6 months to see how bad the dust is. If its an issue I'll muck around with some of the other suggestions posted here. Also, I'm going to try and maximize the front intakes by modding the front panel with a grill or doing something like this http://mnpctech.com/mnpctech-clear-case-pc-panels/corsair-750d-front-plate/corsair-750d-cnc-milled-vented-front-bezel-plate.html Should hopefully help with overall temps, as the case does seem a bit restricted by its front panel.

I'll have the build done in the next couple of weeks, so if anyone else was using any of the info here I'd be happy to share my test results when I'm done building.