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More case fans than sysfan headers on motherboard

Last response: in Components
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September 9, 2010 4:48:23 PM

Cases today are coming with more fans that a rock concert. Any case I'd get seems to have at least 4, two top, a front, and a back. If looked at some with 5.

Mobos seem to have, at most, 3 sysfan headers. So I'm at least one short. There are a number of ways to handle this. I want to get a sense of what builders are doing.

1) Just wire the case fans right to the power supply. Simple, cheap, but no control/monitoring.

2) Wire what you can to the mobo, and just wire what's left to the PS. More control, works, cheap, but a bit clugey.

3) Split the output from the sysfan headers to multiple fans. Have found cables to do this. would have to cut off one of the fan speed lines. How much load can a single sysfan header handle?

4) Fan controller. Explicit control of everything, but on the case, not from software. Also, extra cost.

So what are people doing with this.

Thanks
a b ) Power supply
a b V Motherboard
September 9, 2010 4:56:23 PM

What case are you buying? Some of the 5 fan cases come with fans that are meant to be connected to the PSU (Antec TriCool fans for example).

I think you listed all four solutions, though for #3 , you really don't have to cut any wires. IIRC, the Mobo fan headers are usually 12Ws.
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a b ) Power supply
a b V Motherboard
September 9, 2010 6:13:18 PM

Just wire the case fans into the PSU - there's no need to monitor them, so no need to drop them into a motherboard header.

Otherwise it's fan controller time (or fans with speed switches on them like Antec TriCool).

Personally I don't see the point in monitoring or controlling case fans.
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September 9, 2010 6:25:44 PM

Right now I'm leaning toward the Lancool K62. I've also looked at the Coolermaster 690II advanced and Lian Li PC-B25.

As far as the sysfan headers do you mean 12 volts or 12 watts? I know 12 volts is standard. i just need to know if they have the amperage to drive more than one fan a piece.

Timop said:
What case are you buying? Some of the 5 fan cases come with fans that are meant to be connected to the PSU
(Antec TriCool fans for example).

I think you listed all four solutions, though for #3 , you really don't have to cut any wires. IIRC, the Mobo fan headers are usually 12Ws.

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a b ) Power supply
a b V Motherboard
September 9, 2010 6:29:00 PM

BigStack said:
Right now I'm leaning toward the Lancool K62. I've also looked at the Coolermaster 690II advanced and Lian Li PC-B25.

As far as the sysfan headers do you mean 12 volts or 12 watts? I know 12 volts is standard. i just need to know if they have the amperage to drive more than one fan a piece.

Its 12V @1A, which gives you 12W. A normal case fan uses no more than 3W.

Though the K62 has only 4 fans, and the 690II only 3, which fits fine on the Mobo headers.
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Best solution

a c 248 ) Power supply
a b V Motherboard
September 9, 2010 6:31:07 PM

The only fan that absolutely, positively needs to be connected to a fan header on the motherboard is the cpu heatsink fan. The pc will not operate if the cpu heatsink fan is not connected to the cpu fan header

The cpu heatsink fan is usually (but not always) the only fan that can be monitored and speed adjusted by the system. There's quite a bit of variation even by the same manufacturer. My motherboard has 3 fan headers but only monitors and controls 2 fans.

Connecting two fans to one fan header on a motherboard is not recommended.

The easiest thing to do is to simply connect the extra case fans to the power supply. Otherwise, if you really want to control the speed of the extra fans, then you will have to get a fan controller.

I have the Lancool Dragon Lord PC-K60W with the narrow side window. Ventilation, airflow, and cooling are excellent. However, I added a second fan to the front panel to balance the airflow and create a wind tunnel effect:

http://www.johnnylucky.org/dragon-lord/index.html
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September 9, 2010 6:33:06 PM

I thought about that for the 690II, but I really don't want this issue determining my case.

Timop said:
Its 12V @1A, which gives you 12W. A normal case fan uses no more than 3W.

Though the K62 has only 4 fans, and the 690II only 3, which fits fine on the Mobo headers.
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a b ) Power supply
a b V Motherboard
September 10, 2010 4:19:40 PM

Your Option 3 is the best in my opinion. And I agree that you must snip some yellow wires. When you connect two or more fans in parallel off one mobo fan pinout, you DO need the black lines together (Ground) and red lines together (varying + VDC), but NOT the yellow lines. Those lines bring a pulse chain back to the mobo from the fan motor. Running more than one pulse chain from different fans at slightly different speeds into the mobo speed measuring circuit is bound to confuse it! So connect to the mobo only ONE yellow line per port, and live with being unable to measure the speeds of any fan whose yellow lead is not connected. I do NOT understand why adapters are sold that connect the yellow leads in parallel, too!

In earlier posts I have read people's opinion that most fan pinouts on mobos can handle TWO normal 3-pin fans, but maybe not more. The limit is not the steady-state operation (e.g., 3W fans in parallel on a port with 12W capacity). The limit is in the START-UP current necessary to start TWO or more fans simultaneously. It is common that start-up current may be twice the running current.

By the way, the Antec TriCool fans mentioned in one post are an interesting example of one route. They are intended to plug into a PSU output that is always 12 VDC. But they also have permanently attached a little 3-position switch on the end of a short cord. The idea is that you manually set each fan to Low, Med or Hi speed with its switch and leave it that way. So you can set speeds other than full speed for each such fan individually, but it's not something you would change often because you have to open the case for access to the little switch.
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September 17, 2010 1:53:11 PM

Best answer selected by BigStack.
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