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Powering and Controlling Fans

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January 24, 2013 8:13:28 PM

I'm in the very early stages of researching components for my first gaming build (researching motherboards, currently) and I'm utterly confused about fans and air cooling—specifically, how the fans are powered and controlled. I've divided my question into several sections.

Let's say I buy a case that has space for 2 front fans, 2 side fans, , 2 top fans, one floor fan, and one rear fan.

1. 8 fans is more than the standard motherboard can handle, am I right? So which fans would I plug into the motherboard, and which fans would I plug directly into the power source?

2. Further, how do I know how many fans my motherboard can handle? I mean, what do the fans even plug into? I've heard something about 3- or 4-pronged plugs, so which should I look for when choosing a motherboard? And how many?

3. For the fans that don't plug into the mobo, but the PSU directly, I guess I need to be making sure that my chosen PSU will have adequate connectors for the fans, no? Or can I be pretty sure that as long as I'm not buying a cheap-o PSU I'll get what I need in terms of PSU fan connections?

4. And then what about LED fans? Do their LED plugs connect to the mobo or the PSU? And again, do I need to be making extra certain that my PSU/mobo will have the appropriate number and kind of connectors for these LED plugs?

5. Then there's the question of controlling the fans. I know I can buy a fan controller panel, or choose a case that has such an option pre-installed, but what should I be looking for in such a controller (assuming I decide to get one at all)? I'm the type of person who would forget to turn the fans up when I start gaming... are there controllers out there that can detect the case temperature and that I could program to increase/decrease fan speed at certain temperature thresholds?I mean, I saw a couple controllers that have warning beeps and stuff, but ideally, I'd want to just set my fans up and forget about them.

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a b V Motherboard
January 24, 2013 10:23:55 PM
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1. The one fan that MUST be plugged into the motherboard fan header is the CPU fan. Other fans may be plugged into appropriate mobo fan headers, OR into the PSU using Molex connectors, OR into the fan controller that you mentioned.

2. The motherboard can handle as many fans as there are fan headers.

3. All you need is one PSU cable with a Molex connector. You can "daisy-chain" all the fans to this connector. However, they will all run at full rated RPM.

4. LED fans do have a slightly higher power draw and connect these directly to the PSU (even though the mobo may be able to handle the fan).

5. Fan controllers look nice and dress-out the computer quite well. Set the individual fans to the lowest RPMs that will give you acceptable temps. This will need some experimentation.

Personally, I like to plug in my fans (HAF X case) directly to the PSU. Doing so will reduce the power draw of the motherboard. Less power means less heat (motherboard). But remember, the CPU fan must be plugged into the "CPU_FAN" header on the motherboard.

Read up some more on this topic and you will get a better picture. Right now you are asking the right questions.
January 25, 2013 3:25:33 AM

Ubrales said:
1. The one fan that MUST be plugged into the motherboard fan header is the CPU fan. Other fans may be plugged into appropriate mobo fan headers, OR into the PSU using Molex connectors, OR into the fan controller that you mentioned.

2. The motherboard can handle as many fans as there are fan headers.

3. All you need is one PSU cable with a Molex connector. You can "daisy-chain" all the fans to this connector. However, they will all run at full rated RPM.

4. LED fans do have a slightly higher power draw and connect these directly to the PSU (even though the mobo may be able to handle the fan).

5. Fan controllers look nice and dress-out the computer quite well. Set the individual fans to the lowest RPMs that will give you acceptable temps. This will need some experimentation.

Personally, I like to plug in my fans (HAF X case) directly to the PSU. Doing so will reduce the power draw of the motherboard. Less power means less heat (motherboard). But remember, the CPU fan must be plugged into the "CPU_FAN" header on the motherboard.

Read up some more on this topic and you will get a better picture. Right now you are asking the right questions.


Thanks, Ubrales :)  Glad to hear I'm on the right track. So fan headers are just those 3-pin (or in the case of the CPU, 4-pin) connectors? I take it the 4th pin on the CPU fan header is actually somehow associated with temperature detection?

And if I daisy chain, say, 3 fans to the PSU's molex connector, will that not mean that those fans will run at 1/3 of their max rpm?

I really appreciate all of your help; it's helped a lot in terms of understanding how I'll want to set up my cooling system.
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a b V Motherboard
January 25, 2013 3:33:47 AM

SyntaxSocialist said:

And if I daisy chain, say, 3 fans to the PSU's molex connector, will that not mean that those fans will run at 1/3 of their max rpm?

No. With the exception of a tiny bit of voltage sag, all the fans will more or less run at full speed.
a b V Motherboard
January 25, 2013 12:16:37 PM

SyntaxSocialist said:
Thanks, Ubrales :)  Glad to hear I'm on the right track. So fan headers are just those 3-pin (or in the case of the CPU, 4-pin) connectors? I take it the 4th pin on the CPU fan header is actually somehow associated with temperature detection?

And if I daisy chain, say, 3 fans to the PSU's molex connector, will that not mean that those fans will run at 1/3 of their max rpm?

I really appreciate all of your help; it's helped a lot in terms of understanding how I'll want to set up my cooling system.

The motherboard fan headers will be clearly marked as "SYS_FAN", "PWR_FAN", or similarly. If you plug in a 4-pins connector fan to any of these headers, then you have the capability of controlling the fan speed by settings in the BIOS; commonly by "IF _ THEN" statements.

By "Daisy-chaining" you will be supplying full voltage to all the daisy-chained fans, and they will all run at full rated RPMs. Each fan will come with a 'Male Molex' as well as a 'Female Molex' connector.

Start the daisy-chain by connecting one fan's male Molex to the PSU (female) Molex. Then connect the second fan's male Molex to the first fan's female Molex, and so on until all the fans are daisy chained.
January 27, 2013 6:58:51 PM

Best answer selected by SyntaxSocialist.
January 27, 2013 6:59:30 PM

Thanks so much! All of this info has been/is immensely helpful!
a b V Motherboard
January 27, 2013 7:38:08 PM

SyntaxSocialist said:
Thanks so much! All of this info has been/is immensely helpful!

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