Question Just a general question

William Sage

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May 24, 2015
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my question is more along the line of plugging what fan into what fan. Trying to understand what fans can you not plug into the motherboard. https://www.newegg.com/noctua-nf-a14-ippc-2000-pwm-case-fan/p/N82E16835608047?Item=9SIAADY4P65808 this fan for example and the differences between pwm fans and not pwm fans? Is there a limit to how many fans i can connect to a single fan header?

merged post below:

In fact if i read it correctly you can only use a max up to 12v on fan headers? If thats the case Amazon.com: Noctua NF-F12 iPPC-2000, Heavy Duty Cooling Fan, 3-Pin, 2000 RPM (120mm, Black) : Electronics seems to offer 12V variants so in theory i can pop those on my motherboard fan headers?
 
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Paperdoc

Polypheme
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All standard fans for computers now use a power supply of 12 VDC. The differences between older 3-pin Voltage Controlled fans and modern 4-pin PWM fans are in other details of how their speeds are controlled, not in their supply voltages. The speed of a 3-pin fan can be controlled only by varying the Voltage supplied to is on Pin #2 from 12 VDC (full speed) down to 5 VDC (min). For a 4-pin fans the Voltage on Pin #3 is always 12 VDC, and the fan has a special chip that uses the new PMW signal from Pin #4 to control its speed. A 3-pin fan cannot do that because it has no such chip. Because those methods of controlling fan speeds are different, you should not connect fans of those two different designs together on one header. On most mobos now, all headers have 4 pins, and there is an option in BIOS Setup for each header separately to have them use either Voltage Control Mode (aka DC Mode) or PWM Mode.

The limit on multiple fans on one header is on CURRENT drawn by the total load. A normal mobo fan header can supply up to 1.0 A max current per header. Within that limit you can connect several fans to the header using a SPLITTER. That is a simple device that merely connects all the fans' power supply lines to the header so that ALL power for all of the fans on that Splitter / header comes only from the header, and thus is subject to that current limit. Fan specs should include both Voltage and max Current specs, although some specify in WATTS rather than in Amps. It happens the one you linked to provides all three specs: 12 VDC, 0.18 A max, 2.16 W max.

A SPLITTER may appear visually as a group of cable "arms", as a small circuit board with exposed male (with pins) ports, or as a closed box with its ports recessed inside openings. It has only two type of connections: one "arm" with a female connector to plug into a mobo header, and two or more "arms" (ports) with male connectors to plug in your fans. A 4-pin SPLITTER can distribute all mobo signals to its fans and thus can be used with either fan type, subject to the 1.0 A max current limit.,

If you need to connect to ONE header many fans so that the total load exceeds the 1.0 A limit, you need a different type of device called a HUB. This may look very much the same as a SPLTTER but its distinguishing difference is that it has one THIRD type of "arm" that must plug into a SATA or Molex power output connector from the PSU. The Hub draws all power for its fans from the PSU directly, and none from the mobo header, so it is not limited to that 1.0 A max draw. (It does have a higher limit of 4.5 A max because of details of its connection to the PSU.) The Hub does distribute to all its fans the PWM signal from Pin #4, but this does NOT cause a load limit on the header. Note, however, that the standard Hub design distributes to its fans a fixed 12 VDC power supply on Pin #2 and the PWM signal on Pin #4, so it can control the speeds ONLY using the new PWM Mode, and cannot control the speed of a 3-pin fan. (There are a FEW other Hub designs that do not have this limit on uses.)

Almost all computer fans generate a Speed signal (a train of 5 VDC pulses, 2 pulses per revolution) and send it back to the host header on Pin #3. But the header can deal with only ONE pulse train - two or more mixed together causes huge confusion and mis-readings of speed. So any Splitter or Hub will send back to the host header the speed signal of only ONE fan and completely ignore all the others - those will never be seen anywhere. This has NO impact on ability to control speed. It does impact the header's secondary function. Each header monitors the speed signal for FAILURE and will pop up a screen warning if its fan fails. But of course it cannot do that for ALL fans on a Splitter or Hub. So when you use these devices, from time to time YOU need to observe all fans and ensure they all still are working.
 
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