# push/pull rad, worth it?



## erixx (Nov 10, 2017)

Hi!
I have a triple rad and I wonder if adding 3 more fans below to it would make a difference.
Somewhere I read that pump speed is much, but very much more important than rad fans speed or quantity.
I have spare fans so it's not a cost problem, but it makes my build more complex.

I'd also appreciate recommendations regarding the fans powering. Should I just join 6 fans into one onboard fan header? Or better not? Or use 2? At the moment, I have 3 in 1 cables.

What do you think?


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## Durvelle27 (Nov 10, 2017)

Yep


Edit: It’s safer to give each fan individual dedicated power.


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## erixx (Nov 10, 2017)

spaguetti cabling incoming! .... 2x 3x1 would be ok, still

but main question is if putting 6 fans on a rad will be a good idea


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## jboydgolfer (Nov 10, 2017)

I've never had a noticeable or  justifiable difference in temperature from adding fans to the other side. I just leave it to pull or push but never both.  I think people do it ,just do it more often than not ( and keep in mind I don't consider 3 to 5° worthwhile).

 Purchase good fans & you won't need to do it. Unless of course you're already dead set on doing it.  IMO, I think a lot of it is nit picking & placebo effect


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## thebluebumblebee (Nov 11, 2017)

erixx said:


> Should I just join 6 fans into one onboard fan header?


Be very careful about drawing too much wattage through a motherboard header - you can burn them out or worse.  Much safer to get something like http://www.phanteks.com/PH-PWHUB.html


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## dorsetknob (Nov 11, 2017)

Buy dedicated fan controller  to use
if you push/pull with 3+3 fans while the Fan header MAY handle the power draw its Safer in the long run to use a dedicated Fan controller


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## manofthem (Nov 11, 2017)

erixx said:


> I have a triple rad and I wonder if adding 3 more fans below to it would make a difference.
> Somewhere I read that pump speed is much, but very much more important than rad fans speed or quantity.
> I have spare fans so it's not a cost problem, but it makes my build more complex.



I initially ran push/pull, but eventually opted to just push and the difference wasn't huge, pretty negligible.  Later added extra rad space instead.  



erixx said:


> I'd also appreciate recommendations regarding the fans powering. Should I just join 6 fans into one onboard fan header? Or better not? Or use 2? At the moment, I have 3 in 1 cables.
> 
> What do you think?



I wired 3 fans together into one connection and run them off the board, but now they're plugged into a splitter, something along these lines; plugs into the psu connector.  It's been running that way for a few years and going strong til today.  


Also just wondering, what are you watercooling: cpu only or cpu and gpu?


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## lZKoce (Nov 11, 2017)

Temperature-wise, I think it benefits. I earned 2-3 degrees with push-pull on my Kraken, but it all depends if you really need this. Also, if you will have 10 fans in the PC, that might be a complication : noise-wise and powering them all. Driving 3-4 fans off one MB header-> please check your MB product page/manual. It should say the maximum power output. It says on mine at least, but I have a Lamptron fan controller anyway.


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## CAPSLOCKSTUCK (Nov 11, 2017)

I use this

molex to fan header


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## erixx (Nov 11, 2017)

manofthem said:


> Also just wondering, what are you watercooling: cpu only or cpu and gpu?



Good one! I run both in one loop, overclocked, and recently I have returned to a little benching. That is the only reason, maybe, for "over-engeneering" again 
Maybe I should just fix some heat issues lowering voltages (went from 1,3 to 1,27 Vcore (1,29 SA 1,28 VCCIO ) and that solved one benchcrash due to heat... now passing RealBench at cpu=4800Mhz)


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## londiste (Nov 17, 2017)

temperature-wise, the difference is not that big but it does seem to allow lower fan speeds. which kind of makes sense when you think about it.


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## jboydgolfer (Nov 17, 2017)

i keep my PC cool for DAYS with elite pro hacker tactics.......


Spoiler: Proper cooling








& for Larger server sized application.......







only Scrubs use fans....Pffft!


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## peche (Nov 17, 2017)

1. avoid using 1 header or connection for moar than 2 fans, use logic that will hurt something,
2. if you already have the fans somewhere there, use'em, if you have the idea to improve cooling, better add another rad to the loop, difference will be max 10C in the best scenario,
3. a great will item to use will  be a molex / header spliter for moar fans, like the mention in post  #9 , pretty useful indeed,



Spoiler: Rajintech pean








according your specs...This case has plenty space for an epic cable management...


according your specs...


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## R00kie (Nov 17, 2017)

How thick is the rad? If its a slim one, there will be no difference, you're just adding more noise to your system.


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## EarthDog (Nov 17, 2017)

erixx said:


> Hi!
> I have a triple rad and I wonder if adding 3 more fans below to it would make a difference.
> Somewhere I read that pump speed is much, but very much more important than rad fans speed or quantity.
> I have spare fans so it's not a cost problem, but it makes my build more complex.
> ...


Where to start....

Are your current temps OK? If so, I wouldn't bother... its just extra noise for a couple degrees C different.

Pump speed isn't terribly important. You need to keep around 1-1.5GPM flow for optimum results. Faster it is diminishing returns, slower, you lose a bit of performance. 

DO NOT place 6 fans on to one header unless you know how much amperage it puts out. Some headers are high amp headers and can support 2A(24W) and can piggy back a few fans. Most are around 1A(12W) however. The stick on the fan hub will show how much power each uses. I am sure you can do the math at that point.


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## erixx (Nov 17, 2017)

Thanks all, for your useful comments. My rad is the EK Extreme 360, a fatty.  So far I have gone the voltage reducing route and that has help a lot. Next week i will also install a twice as big reservoir and then I will see if anything like pull/push fans is still necessary.

My temps now: during gaming they stay under 60 ºC. Benching they crawl up to 80 ºC. (CPU). Did a long run with RealBench and the lower voltages and it went flawless staying at said 80ºC. As I mentioned somewhere above, my question started when at 1,32v core it crashed, the temps were close to 90ºC. So now it seems all solid. (CPU@4800Mhz all 6 cores.)

Thanks again! Will upload a pic when the new parts are added.


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## EarthDog (Nov 17, 2017)

What does a resivoir have to do with temps?

I think you would see better results from delidding than adding more fans. It isn't so much that you don't have enough rad or fans, but the heat isn't being transfered well from the CPU to the block due to the TIM used.


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## erixx (Nov 17, 2017)

Moar liquid = moar cooler. The stock reservoir is very small (12cm).

Delidding, ok ok ok, during holidays, maybe


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## EarthDog (Nov 17, 2017)

No... it means it takes just a bit longer to warm up/normalize. It does NOT mean more cooling. 

Now, if you used a POOL, I would agree, but a few ounces of water isn't going to do much of anything, sorry.


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## John Naylor (Nov 26, 2017)

1.  Push / pull will add about 30% more cooling ability.  Push has the edge < around 1750 rpm ... pull does little better > 1750 rpm.  This won't be true for every rad and every fan but "on average".  See articles at MartinsLiquidLab  ... or d/l the rad info here

http://www.overclock.net/t/1457426/radiator-size-estimator

2,  Fan headers are typically rated at 1 amp... you want to be a bit below that to allow for inrush current.   For 1250 rpm 140mm fans, I will do up to 6 ... w/ 1500 rpm up to 5, w/ 1800 up to 4.    I recommend the Phanteks Fan Hub as its versatile... for PWM fans on PWM header Swiftech works well... for DCV headers w/ DCV fans, can also use the PCB hubs from ModMyToys.

3.  There's no real advantage anymore to spending twice as much for PWM fans ... most DCV fan designs today go down to 25% speed w/o an issue and don't exhibit the low speed humming / clicking that sometimes occurs w/ PWM.  The Phanteks Hub can be used w/ up to 11 fans on PWM header w/ the SATA power cable.  If ya use power cable on DCV header, you lose speed control so limit number of fans per Item 2 above (< 1.0 amps).    I have 4 channels ..

a.  CPU & CPU-OPT (PWM) => twin pumps
b.  CHA 1 (DCV) => Hub No. 1 => (6) 1250 rpm fans on 420mm rad
c.  CHA 2 (DCV) => Hub No. 2 => (4) 1250 rpm fans om 280mm rad
d.  CHA 3 (DCV) => Hub No. 3 => 6) 1250 rpm case fans

All fans range from 350  -  850 rpm under fan curve, rad fans ran ramp down after temps drop over 60 seconds to  drop coolant temps.  Fans are set to turn off when temps would call for flows below 325.

4.  Running or PSU (Molex) means no speed control and noise.

5.  There is an advantage to varying pump speed but after 1.00 it starts to tail off and once ya get over 1.25 gpm, it's has sharply diminishing returns.   Pump (35x@ twin pumps) speed curve on my box typically varies  from about 35% to 65% of full speed but it will go to max under Furmark + RoG Real Bench when run together.  CPU will get to mid 70s under ROG Real bench ... the GPUs are at 44c ... they drop to 29C aw/ fans at full speed but fans audible over 850 rpm

6.  A reservoir is a valuable tool as it adds thermal mass ... when exposed to varying loads, your system can chase it 's tail so to speak as fans ramp up during short heave loads and then ramp down when load drops... but "in between" your coolant didn't drop because ya fans ramped down as soon as load dropped.  Result is a fans ramping up and down repeatedly leaving you listening to the whirring noise each time they ramp up.   Use the fan utility in your MoBo package to set ramp down times once you add a reservoir.  Another function of the reservoir is to trap any "off-gassing".  You can bleed your loop, after installing everything and soon after you will see or hear gas bubbles in the loop.  Ignore it and ya can lose  a pump.   Ya still have to pay attention as air can be trapped up ant highest point in ya loop but res will trap most of it.

7.  For me, it';s just as much about noise as temps ... if i can tell PC is running when I walk in room and sit down in front of KB, (screen asleep) ... then poppa ain't happy.  It's not quiet I'm looking for, it's dead silence.  Fans matter.  I prefer more fans to higher rpm fans.  Many of the water cooling guru choices from days gone by , don't really work so well on the low - medium fpi rads that dominate the marketplace.  We don't need the SP that for example the ole he old Nidec (Scythe) GTs provided.  I was shocked when in testing, taking the Noctua fans off a Noctua cooler dropped CPU temps 6C at the same 1200 rpm speed.

http://www.overclockersclub.com/reviews/phenteks_f140/3.htm

If ya have a Phanteks case, they are golden ... in another case I will use the Phanteks or new Silent Wings 3  which came out after this test

http://www.silentpcreview.com/article1345-page7.html

8.  One last note if using PWM fans, don't gang more than 4 or 5 Corsair fans on a single channel as they lose speed control

http://www.overclock.net/t/1506812/the-best-pwm-rad-fans-going-to-be-very-exact-spec-needs/30

9.  Not a fan of fan controllers... the idea of manually adjusting fan speeds to varying loads is just not something I wanan deal with.

So is push / pull worth it ?  If ya not happy with ya temps and no more mounts for rads, based upon martins testing, you can expect an improvement of about 30% or so ... if it's a cheap aluminum rad or a CLC, not worth the time and effort.


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## londiste (Dec 2, 2017)

John Naylor said:


> 9.  Not a fan of fan controllers... the idea of manually adjusting fan speeds to varying loads is just not something I wanan deal with.


I dislike fan controllers for the same reason. However, you can get best from both worlds, for a price - configurable hardware controllers (with hardware sensors).
There are others but I am currently using Aquaero (5 LT): https://shop.aquacomputer.de/index.php?cPath=62_63_64


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## EarthDog (Dec 2, 2017)

#6.... no. Adding a couple oz of water isnt going to help much at all.

#9. Fans arent/cant be set it and forget it? Whos running on the ragged edge of temps for normal activities that cranking a set of fans, lowering temps a few c, will resolve? There are also fan controllers which will work based on temps.


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## erixx (Dec 6, 2017)

This is the final build for now. I am quite happy because I pass gloriously all stress tests.
For now no added fans. The upper 3 fans are off most of the time, and only start when temps are high.
I am not looking for records, but I am doing just fine in 3DMark, RealBench, Aida64 etc. And gaming at 4K...
Of course sugestions are welcome.





And for a more ambience impression, this contextual one.


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## John Naylor (Dec 10, 2017)

EarthDog said:


> #6.... no. Adding a couple oz of water isnt going to help much at all.
> 
> #9. Fans arent/cant be set it and forget it? Whos running on the ragged edge of temps for normal activities that cranking a set of fans, lowering temps a few c, will resolve? There are also fan controllers which will work based on temps.



On # 6  . . . Please read again.... nothing was said about coolant temps..... it's mostkly about noise and you can certainly observe fan speeds and record as we have.  And it's not a couple of ounces of water, it's 10 ounces and a surface a surface area of 16+ square inches.  Why does surface area matter ?  Think about the 90 - 130 watt CPU that water block is only able to keep at 75C with its tiny surface area versus the 300 watt GPU that water block is able to keep < 40C.

1.  You have to be using the proper tools.  If using P95 which is virtually useless since Sandy Bridger.   Yes it doesn't matter significantly as P95 will maintain a relatively constant load and yes a reservoir will have limited impact.   But remember, as was said, the radiators remove ONLY about 60% of the calculated heat load.  The other 40% comes from the fact that a) your system never sees the max heat load because **in the real world** and **using real applications / games** the heat load is not constant.  A large 250 ml reservoir has a substantiall surface area and it acts just like an air cooler radiating heat from its surface, as is your tubing, radiator shroud, block surface area and everything else that is warm to the touch inside the PC ... the PC which has the interior case air volume exchanged with fresh cool air several times per second.

2.  Again in the real world, your system sees periods of light and heavy loads.  Watch your CPU temps under RoG Real Bench ... they vary significantly.  Run Furmark and watch the curve .... mine starts out at about 26C GPU temp and rises slowly to 44C at which point, under the synthetic non-real world load, it reaches equilibrium.  But in the real world, when paying  a game, the load varies substantially.  You can see the same thing with Intel XTU load curve, the CPU temps follow up down up down up down.    With no reservoir capacity, the coolant temps change in response to CPU / GPU temps very quickly and the temp curve is very jagged.  With a large reservoir, those peaks and valleys are smoothed out resulting in smaller variations in CPU / GPU temps.   As a result, the fans whos speed is controlled automatically (a point you seem to have missed) changes very little

No reservoir ...... 65-75-68-72-70-70-64-76
w/ reservoirs.... 68-72-70-70-70-70-67-73

In both cases the average is 70C (ignoring thermal radiation from reservoir surface) but in one case the changes in fan speed can be heard, in the other not at all.

In addition, a reservoir acts as an air trap for any off gassing within the loop, an air bubble trapped in a loop can otherwise significantly impact performance.

On # 9.   this is 2107 not 1991.   Been building PC's for 25 years and every box that leaves here has been set up to "set it and forget it".   The fans in our test box were set on the day I built the box and 3 years later, I have not touched them since.  Cooling is not just about not frying the PC components, it's also about making the user environment bearable.  And that involves minimizing sound.  Siting at the desk, using your ears, you can not tell the system is on.  Using the fan control utility that comes with the motherboard, I have the system set up as follows:

CPU & CPU OPT Header => Pumps 1 and 2 .
Pumps are set to run from about 40% to 100% of full speed.  I set up a temp / speed curve using the software provided and forgot about it.

CHA_1 header => Fan Control PCB No. 1 => (6) fans on 420 radiator
Fans are set to run from 350 rpm to 1250 rpm.  I set them to shut off when temps are < 30C, they climb thru various speed / temp setpoints to 75C and > 75 they go to 100%.  In response to temp changes, they ramp up to curve speeds over 12 seconds, and ramp down over 100 seconds to expel heat from the coolant after load disappears.  I set up a temp / speed curve using the software provided and forgot about it.

CHA_2 header => Fan Control PCB No. 2 => (4) fans on 280 radiator
Fans are set to run from 350 rpm to 1250 rpm.  I set them to shut off when temps are < 30C, they climb thru various speed / temp setpoints to 75C and > 75 they go to 100%.  In response to temp changes, they ramp up to curve speeds over 12 seconds, and ramp down over 100 seconds to expel heat from the coolant after load disappears.  I set up a temp / speed curve using the software provided and forgot about it.

CHA_3 header => Fan Control PCB No. 3 => (6) Case fans
Fans are set to run from 350 rpm to 1250 rpm.  I set them to shut off when temps are < 35C, they climb thru various speed / temp set points to 70C and > 80C they go to 100%.  In response to temp changes, they ramp up / down to curve speeds over 12 seconds.I set up a temp / speed curve using the software provided and forgot about it for about a year until I made a tweak, not touched it since.

At idle, all my fans shut off... and I don't have to do anything ... when system is under load, fan speed is raised in proportion to the load.  This is simple stuff, and I don't know why this is being seen as a  foreign concept.  I don't care about the "ragged edge of temps" because my system never sees it.  What I care about is silence.   There's no realistic need for a "fan controller" when superior technology exists that has more options, is free and which most certainly can be "set once and forgotten".

The system uses (6) thermal sensors, accurate to 0.1C, which detect:

coolant temps in / out of 420mm rad
coolant temps in / out of 280mm rad
Ambient and interior case air temps

and displays them on a 6 channel digital display in a 5.25" bay at front of PC.

Can take CPU temps down to , 70C at 4.7 Ghz and the twin GPU temps down to 39C,  but at that point fan speeds under stress testing exceed 850 rpm and I can hear the fans... So to avoid buying 30 foot cables and stikcing the PC in another room where I don't have to hear it, I am quite happy with 75C and 44C.  All accomplished without a thought or lifting a finger since day # 1


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