[SOLVED] Connecting lots of fans to CPU fan header

Jan 13, 2021
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Just wondering, how do people go about connecting additional fans to the CPU fan header? I'm curious about how it's done with large radiators.

Would a fan hub be a solution? or how do people usually go about doing this?
 

Paperdoc

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Specify which temperature ... above. Not quite. In virtually ALL mobos, the ONLY choice for which temperature sensor is used to guide the CPU_FAN header is the one inside the CPU chip. This prevents users from making the WRONG choce by mistake. Many mobos DO give you that choice on their SYS_FAN or CHA_FAN headers, though. Thus it MAY be possible to have one of those headers re-purposed to govern their cooling actions by the internal CPU temp sensor.

But there's another solution. The simpler one above is a fan Spltter to connect several fans to the one CPU_FAN header. A Splitter has only one input "arm" that plugs into that header, and two or more male (with pins) outputs for fans. It gets no power from anywhere else, so this sytem IS limited to the max current available from the CPU_FAN header. But note that this is really the only way to control the speeds of THREE-pin fans that use the older Voltage Control Mode (aka DC Mode). IF the fans you are going to use are the newer FOUR-pin fans (aka PWM Mode fans), then there is a different device you can use provided that the mobo CPU_FAN header does (or can be set to) use PWM Mode, and almost ALL current mobos make that possible. A HUB has the same input (female) connector and several outputs for fans, but it also has a third "arm" that must connect to a power output (either SATA or 4-pin Molex) from the PSU. All power for the fans comes from there, so you are not limited by the current capacity of the CPU_FAN header. That is the simpler way to connect many fans to one header. As I said, though, a HUB normally works only with a header configured to use PWM Mode, and with 4-pin fans.
 
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jay32267

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If you use a splitter....just be careful not to go over the current delivering capability of your motherboards header.

If you can't find that number.....use 1 amp as the maximum....and that is the total of all the fans connected to that header.
 
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Jan 13, 2021
2
0
10
0
You can get a splitter cable (look for fan splitter cable on amazon or ebay)
If you use a splitter....just be careful not to go over the current delivering capability of your motherboards header.

If you can't find that number.....use 1 amp as the maximum....and that is the total of all the fans connected to that header.
Okay thank you that's great to know :)

Also curious, what about in a situation where there are more fans than what the header can safely supply power to? Like let's say a total of 6 fans, what methods do people use to safely power them all up?
 

jay32267

Champion
One easy way (if you were going to run them at 100%...like for case fans) would be to come right off the power supply with a splitter. There would be no 1 amp limit.

The CPU fan header is intended for JUST the CPU fan(s) because it is temperature controlled....so I wouldn't be splitting that for lets say....case fans.
 
Nov 17, 2020
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One easy way (if you were going to run them at 100%...like for case fans) would be to come right off the power supply with a splitter. There would be no 1 amp limit.

The CPU fan header is intended for JUST the CPU fan(s) because it is temperature controlled....so I wouldn't be splitting that for lets say....case fans.
Depending on board and Bios, it can be possible to specify which temp drives the fan header, no?
 

Paperdoc

Champion
Ambassador
Specify which temperature ... above. Not quite. In virtually ALL mobos, the ONLY choice for which temperature sensor is used to guide the CPU_FAN header is the one inside the CPU chip. This prevents users from making the WRONG choce by mistake. Many mobos DO give you that choice on their SYS_FAN or CHA_FAN headers, though. Thus it MAY be possible to have one of those headers re-purposed to govern their cooling actions by the internal CPU temp sensor.

But there's another solution. The simpler one above is a fan Spltter to connect several fans to the one CPU_FAN header. A Splitter has only one input "arm" that plugs into that header, and two or more male (with pins) outputs for fans. It gets no power from anywhere else, so this sytem IS limited to the max current available from the CPU_FAN header. But note that this is really the only way to control the speeds of THREE-pin fans that use the older Voltage Control Mode (aka DC Mode). IF the fans you are going to use are the newer FOUR-pin fans (aka PWM Mode fans), then there is a different device you can use provided that the mobo CPU_FAN header does (or can be set to) use PWM Mode, and almost ALL current mobos make that possible. A HUB has the same input (female) connector and several outputs for fans, but it also has a third "arm" that must connect to a power output (either SATA or 4-pin Molex) from the PSU. All power for the fans comes from there, so you are not limited by the current capacity of the CPU_FAN header. That is the simpler way to connect many fans to one header. As I said, though, a HUB normally works only with a header configured to use PWM Mode, and with 4-pin fans.
 
Reactions: b3nj1bb

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