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Push+Pull - How much better is it ?


Salsiccia
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I realise that this is the classic open-ended question that invites the response "It totally depends on your setup and what you want to do", but I know that there are some clever folk here who actually know stuff so I thought I'd throw it out there anyway.

 

It's only just tonight occurred to me that as part of my current project to amp up my cooling setup and introduce RGB fans for a bit of bling, that I now have the opportunity to setup my new H100i RGB Platinum cooler as a push-pull setup. My initial thinking was just swap out the current 1st gen H100i unit with the new one, like for like and get equivalent performance, but with added RGB colour. Now I've realised I can potentially re-deploy my existing 2 x 120mm fans from the old unit as well as the 2 new ML-120mm RGB fans in a push pull setup.

 

Obviously the old fans are not RGB and the new ones are, but in my case I think that's OK. I have no window on my case so can't see inside it so my plan for now is to have the RGB fans mounted on top of the radiator (at the top of the case) where they will be visible through a top mesh grill. The current non-RGB fans will be beneath the radiator, inside the case and thus invisible, so colour is irrelevant.

 

From a controller point of view I have also bought a Commander Pro which at the moment is only going to power control 2 extra 140mm ML RGB fans that I also bought that I haven't decided where to mount yet. The CoPro will connect to an RGB Fan hub to RGB light the 2 new 120mm ML fans on the radiator. So I can power control the 2 old 120mm fans from the commander Pro - I think - please feel free to jump in and correct me if required !

 

From a usage point of view, I am not overclocked and don't stress this machine much so realistically push+pull is probably overkill for the minimal load I am going to generate, but for me its more about - this is a fun exercise to learn about options.

 

The case is quite spacious and I reckon I have room for push+pull at the top.

 

Thoughts? Criticisms? Abuse? All welcome - well maybe not the abuse, but helpful corrective suggestions will be well received !

 

Sal

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Push pull allows you to keep your fans at lower speeds but still get equivalent cooling. The biggest challenge is matching speeds/airflow for non-matching fans. They don't have to be exactly matched but close works better.

 

Outside of that, you seem good. I would suggest that you check out the RGB FAQ linked in my signature.

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I do what i THINK is just pull/pull....pull intake on each side of the rad.

 

i use 4 ml140's, the outside ones being the newer more powerful white ones

 

heres a pic, but i RARELY break the high 20's Celsius, and am overclocked at 4.8, use an rtx 2080, and play hearthstone while i wait to respawn in bo4, both at max settings and running icue + razer shovelware

IMG_0259.thumb.jpg.74b8c30f3a029410da3c5317ded5aa41.jpg

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that being said, i prefer blasting my fans at high volumes because i dont care about much but performance (see my crapy cable job haha...), push pull is to be efficient and quiet.

 

the outside of my case has a a 12v dc cpu fan spinning at 6k, so push pull isnt for me.

 

I think honestly, that you really only need the ml140's as intakes in front of the rad. Run em on balanced, you wont hear a thing and be perfecftly cooled based on your post

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For 120mm base radiators (240/360/480), the benefits of push pull are often somewhat muted. If you are really trying to keep fan speeds low (sub-1000 rpm), then there is a definite improvement. Once you get up to around 1200 rpm, the differences are slight. I don't have any H100i Platinum specific data and no one has shared any on this to my knowledge. However, you can look at the data below.

 

This is pulled from a commonly sited reference point. Both samples are extra thick (50mm+) 240mm radiators. Sample 1 is a 16 FPI radiator (or pretty close to the Platinum) and the Sample 2 is a 9 FPI or easy blow through type for comparison. The other notable point is these tests are with a 300W load, so unless you are hooking this up to your GPU the actual deltas are likely to be about 55-60% of the values shown. However, as you will see, when we get down to a 1C difference at 300W, you know that means it will be a fraction of that with a more normal 135-180W CPU load. Also note as mentioned above, the faster the fans go, the smaller the difference between 1 vs 2 sets. This usually holds true, although there are some weird exceptions with super thick, high density radiators designed for massively high speeds.

 

Note both style radiators have a strong difference in push pull at the 750 rpm mark. Of course, with 120mm fans, 750 rpm is barely spinning and very quiet. Now move up to the 1200-1300 rpm range. This about where fan noise gets noticeable, but not terrible. My limit is about 1500 rpm for a 120mm fan, but I am plenty comfortable at 1200. Here the differential is down to about 1C on both. I'll let you add your own value to that. Now adding the extra set does not hurt anything, but does produce more noise. That is where it becomes very hard to calculate. For example, will 4x120mm fans at 1000 rpm be louder or quieter than 2x120@1250. This is hard to know and predict. In my experience, it is very case, fan, and user specific. I am running push pull on one of my 280mm radiators right now and not on the other identical radiator. This gets me an extra 75W of heat dissipation at a 425W combined load. In this system, that is worth about 4C of coolant temperature. While I don't notice them at lower speeds, the 4x140 stack is most definitely louder as I approach 1000 rpm. There is more gains to be had on 140/280/420 size radiators because of the 140mm fan design.

 

So, if this is about curiosity, by all means try it. If it represents a significant outlay in material costs, changes, and you're not sure about, skip it.

Edited by c-attack
Usual typographical errors
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I'm wondering about this as well. I'm planning on using a Commander Mini to control and sync 6x ML120s (three on either side in a </< config) on my H150i PRO to cool my 9900K. I'm already used to an Air 540 with *seven* 140mm fans in it which are connected to the motherboard headers, so having iCUE coordinating the speeds through the controller will be an upgrade.
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All good info here.

 

Note that push/pull can also help airflow and keep case and component temperatures lower when you have your Radiator set up as an (front-) intake (especially compared to push only, as airflow will usually be slowed down/undirected when pushed through the radiator). But it also depends on the case and how many additional intakes you have, how well your exhaust fans suck air out of the case, etc.. If all your intakes are covered by a Radiator, for example, it'll make more of a difference.

Edited by Glzmo
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that being said, i prefer blasting my fans at high volumes because i dont care about much but performance (see my crapy cable job haha...), push pull is to be efficient and quiet.

 

the outside of my case has a a 12v dc cpu fan spinning at 6k, so push pull isnt for me.

 

I think honestly, that you really only need the ml140's as intakes in front of the rad. Run em on balanced, you wont hear a thing and be perfecftly cooled based on your post

 

Thanks goat, appreciate the feedback. I've only got the H100i so "only" got 120mm fans for the rad, but I did also buy the 140mm twin pack for a couple of other case fans.

 

I think you may be right, I think I'll start with just the 2 x 120mm on the rad for now and keep an eye on them. Since I don't stress it I reckon you're right and anything else is just overkill. If I do step it up later on at least I've got options if I need them.

 

And I didn't mind your cabling - its neater than mine !!! I really need custom lengths though since my case is a little on the large side, so that's a project for down the track. There's always another project just around the corner !!!

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For 120mm base radiators (240/360/480), the benefits of push pull are often somewhat muted.

 

.... < Remainder of excellent post removed in the interests of brevity > ......

 

So, if this is about curiosity, by all means try it. If it represents a significant outlay in material costs, changes, and you're not sure about, skip it.

 

Thanks c-attack - again, an excellent and nicely technical breakdown of the scenario (as an IT professional I do appreciate relevant and well worded technical info - it doesn't have to be full of useless jargon to be useful!)

 

I think after taking everyone's feedback on board, given my scenario of not currently pushing this machine hard at all, I am going to "go vanilla" for the time being. Then once I've got iCue all set up and reporting my numbers accurately then I can look to see where I can most economically either improve performance, or jazz up the bling !!

 

[i think it was Zotty who warned me in another thread that once you dip your toe in the RGBz pool there's no turning back !!!]

 

As an aside I have now (as of 2 hours ago) also just brought home a brand new Corsair HX1000i power supply to add to the mix. So will be curious to see what numbers that reports to iCue as well.

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All good info here.

 

Note that push/pull can also help airflow and case temperatures when you have your Radiator set up as an intake (especially compared to push only, as airflow will usually be slowed down/undirected when pushed through the radiator). But it also depends on the case and how many additional intakes you have, how well your exhaust fans suck air out of the case, etc.. If all your intakes are covered by a Radiator, for example, it'll make more of a difference.

 

Good point Giz. You've just taken this into the classic area of "Should my rad be exhaust or intake". I've done lots of reading on this and I understand both sides of the argument and this really is a "horses for courses" area. The decision I've made in my case is to make my rad exhaust. Main reason is I can't get the rad to the front of the case where it would be most useful as intake due to the length of the tubing in my "not small" case. It reaches to the top of the case above the CPU perfectly. So with my 2 front fans as intake and the 2 120mm rad fans and another 140mm rear fan as exhaust that gives me the closest to balanced airflow that I think I can get. I will still be slightly positive pressured, but actually maybe not when I take into account the resistance that the rad will introduce to that exhaust path. It'll be close enough to 50/50 that I reckon it will do me.

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i actually just put a fan lying on the floor of the case, blowing cool air up into the rad. might be worth checking out

 

Interesting thought goat. I do have a front fan at the bottom of the front plate which will probably be one of the 2 ML-140s I bought. That was going to be to cool the PSU which is at the back of the case, also down the bottom. There are 2 HDD cages down there as well, which also have 2 fans in a shroud, but I won't be using them so they will get removed to allow for airflow. Potentially I can direct that air up towards the rear exhaust, but I'm pretty sure there's a baffle above the top of the PSU area making this bottom chamber effectively isolated, but I could repeat that setup above the baffle - there's currently a 200mm fan there that I currently have disconnected, but will probably wire in now.

 

Thanks for the thought !

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