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Cpu fan duct setup

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July 26, 2010 6:43:13 AM

Hi!

How should I connect the fans for my cpu heatsink? I am planning on having a fan and a duct bring cool air to the heatsink, with a push pull setup on it, before the back case fan pulls out the now hot air. There is, in other words, 4 fans connected to cpu cooling. Should I connect them all to the mobo? None of them? I have a fan controller, but have heard that the duct intake and outtake fans have to have the same cfm. Is that true? Wouldn't that mean the same source (mobo or fancontroller channel) has to controll them all?

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a c 103 à CPUs
July 26, 2010 7:46:54 AM

Ok, First out, what heatsink are you having on there? Standard unit or aftermarket shiny?

your rear exhaust fan doesnt count as a cpu fan, only the ones attached to your H.s count, at least one of which should be plugged into your Cpu fan header on the Mobo so your system can read what the fans doing and let you know like in speedfan for example.
your rear exhaust can plug into the cha fan header if you have a small 3pin connector on that, or else a normal Molex from the psu will do,
The argument for balanced airflow, intake/exhaust will go on forever tbh, its usually a good idea to have it reasonably the same imo, but others will vary on that :p 
Personally, I'm not sure that ducting straight to tthe H.s is going to help any,(if at all) if your having a push/pull setup, you'd be better having a front-back airflow going and no ducting in the way.
See what others have to say though before you take my advice :p 
Moto
July 26, 2010 8:45:08 AM

Motopsychojdn said:
Ok, First out, what heatsink are you having on there? Standard unit or aftermarket shiny?

your rear exhaust fan doesnt count as a cpu fan, only the ones attached to your H.s count, at least one of which should be plugged into your Cpu fan header on the Mobo so your system can read what the fans doing and let you know like in speedfan for example.
your rear exhaust can plug into the cha fan header if you have a small 3pin connector on that, or else a normal Molex from the psu will do,
The argument for balanced airflow, intake/exhaust will go on forever tbh, its usually a good idea to have it reasonably the same imo, but others will vary on that :p 
Personally, I'm not sure that ducting straight to tthe H.s is going to help any,(if at all) if your having a push/pull setup, you'd be better having a front-back airflow going and no ducting in the way.
See what others have to say though before you take my advice :p 
Moto


Have a Noctua D14, with a Kama Bay in the front which will be ducted to the front-facing 120mm fan on the Noctua. The goal is not to achieve better cooling, but more silent cooling. :)  I am hoping for a completely silent rig (only the sound of air moving) and the duct to the cpu is just one part.

What I am worrying about is that people say that since a duct is airtight, the fans on both ends have to have the same CFM. Don't know ho0w important it is really, but if it is important, I would have to have all the fans (Noctua 140mm, Noctua 120mm and the front fan on the kama bay) at the same cfm and on the same channel. Sure, I can try to calculate the cfm and adjust the voltage at a % of the fancontroller supplied oen so the CFM's match, and the fancontroller should be able to handle the three fans (Lamptron FC-5) but do I have to have them all on the same controller channel? Is the CFM-balance important?
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a b à CPUs
July 26, 2010 11:38:06 AM

inquartata said:
Have a Noctua D14, with a Kama Bay in the front which will be ducted to the front-facing 120mm fan on the Noctua. The goal is not to achieve better cooling, but more silent cooling. :)  I am hoping for a completely silent rig (only the sound of air moving) and the duct to the cpu is just one part.

What I am worrying about is that people say that since a duct is airtight, the fans on both ends have to have the same CFM. Don't know ho0w important it is really, but if it is important, I would have to have all the fans (Noctua 140mm, Noctua 120mm and the front fan on the kama bay) at the same cfm and on the same channel. Sure, I can try to calculate the cfm and adjust the voltage at a % of the fancontroller supplied oen so the CFM's match, and the fancontroller should be able to handle the three fans (Lamptron FC-5) but do I have to have them all on the same controller channel? Is the CFM-balance important?


Take a look at the this review of the D14 using the stock (different) fans or two and three of the same type.
July 26, 2010 1:28:39 PM

Nice review but it fails to mention soundlevels which is what I am interested in. Also, even if I would splurge out and buy two more P14s the kama bay can only hold a 120mm fan.

So...it seems to be that using several of the same kind of fan is good for airflow on the D14 in specific, and I guess that this is true of fans with the same CFM rating in general. Does this however have negative effects on the fans themselves? Especially when the space is airtight like a duct?

Opinions on how you would connect the fans? I am leaning more and more towards one channel on the LPT5 to controll all fans (except maybe the back one) and adjusting the cfm of the intake to fit the cpufan's (P12) CFM...somehow. Maybe I can use the LNA/ULNA from the D14?
a c 103 à CPUs
July 26, 2010 5:18:16 PM

Have both of your cpu fans on one line off the controller if you like, however your system wont be able to read their rpm's so it'll be up to you to monitor things,
have the exhaust fan at the rear on its own line imo.

I have an 80mm fan set up on a card mounting plate on top of my cpu fan, there is a slight size difference and its 100% on, not cpu controlled at all, I think it alters the stock fans rpm's a touch, but my temps are good and its quiet enough,
Now, as for different cfm fans on the same H.s,
if you have the more powerful fan pulling air into the H.s and pushing it onto the weaker fan, it will force the weaker fan to run faster slightly, probably leading to premature death (The weak fan, not yours :p  )
if you have the more powerful fan in the other position, the weak fan wont be able to provide it with enough air so it will most likely end up 'sucking' on the weaker fan, I think this would be worstcase for both fans life expectancy,
Best thing imo if you have 2 fans on a H.s in pushpull, they should be the same model fan.
The front one (pulling into H.s) plugged on the cpu fan header on mobo, and the 'exhaust' one on a line from your fan controller, that way you can alter that ones speed to suit but it should be roughly equal to the other fans rpms (possibly a touch higher rpms,pull a little bit stronger)
Moto
July 28, 2010 1:41:51 PM

Motopsychojdn said:
Have both of your cpu fans on one line off the controller if you like, however your system wont be able to read their rpm's so it'll be up to you to monitor things,
have the exhaust fan at the rear on its own line imo.

I have an 80mm fan set up on a card mounting plate on top of my cpu fan, there is a slight size difference and its 100% on, not cpu controlled at all, I think it alters the stock fans rpm's a touch, but my temps are good and its quiet enough,
Now, as for different cfm fans on the same H.s,
if you have the more powerful fan pulling air into the H.s and pushing it onto the weaker fan, it will force the weaker fan to run faster slightly, probably leading to premature death (The weak fan, not yours :p  )
if you have the more powerful fan in the other position, the weak fan wont be able to provide it with enough air so it will most likely end up 'sucking' on the weaker fan, I think this would be worstcase for both fans life expectancy,
Best thing imo if you have 2 fans on a H.s in pushpull, they should be the same model fan.
The front one (pulling into H.s) plugged on the cpu fan header on mobo, and the 'exhaust' one on a line from your fan controller, that way you can alter that ones speed to suit but it should be roughly equal to the other fans rpms (possibly a touch higher rpms,pull a little bit stronger)
Moto



Thanks for the advice! Actually with the fan-controller I have and the y-cables I will use (phobya), I believe I will get an accurate reading for the rpms seeing as the y-cables only have a signal-line on one branch of the cables. Here's hoping. :)  As for the CFM-balance I am happy to see that my reasoning is basically the same as yours. Unfortunately, I will have a LED fan on the Kama Bay intake and planning on having a Scythe GT 1850 on the heatsink... I just hope the LED will come out looking horrible so I can switch it out for another Scythe. :D  Then I don't have to worry about the balance. Of course, I could leave the 120mm Noctua there...it is definitely balanced with the 140mm Noctua it comes with and with the fan stated as being selfbalancing I wonder if any negative effects of imbalance might be negated... Hmmm...

Now just to find a way to measure the true CFMs of the fans in question. :D 

Lol at the premature death part. :D 
a c 103 à CPUs
July 28, 2010 2:32:18 PM

inquartata said:
Thanks for the advice! Actually with the fan-controller I have and the y-cables I will use (phobya), I believe I will get an accurate reading for the rpms seeing as the y-cables only have a signal-line on one branch of the cables. Here's hoping. :)  As for the CFM-balance I am happy to see that my reasoning is basically the same as yours. Unfortunately, I will have a LED fan on the Kama Bay intake and planning on having a Scythe GT 1850 on the heatsink... I just hope the LED will come out looking horrible so I can switch it out for another Scythe. :D  Then I don't have to worry about the balance. Of course, I could leave the 120mm Noctua there...it is definitely balanced with the 140mm Noctua it comes with and with the fan stated as being selfbalancing I wonder if any negative effects of imbalance might be negated... Hmmm...

Now just to find a way to measure the true CFMs of the fans in question. :D 

Lol at the premature death part. :D 


sorry for being unclear slightly, you will be able to see/control the rpms from your fan controller, but if you ask hwmonitor or even bios what rpm's your cpu fans are at, it will shrug at you and say 'Que? no signali par cpu fan senor'
thats what I meant by it being up to you to monitor things :) 
if your fans atm are 'selfbalancing' and working well together and if your not an led lover, you can always snip the led wires to turn then off :p  problem solved with no cash outlay, hope you have luck man
Moto
April 22, 2013 5:29:32 PM

would a air duct on the rear channeling air from heat sink fans be a good setup?
!