Fan Splitter Cables

[Arkeus]

I have an Asus z170-e motherboard. It has one CPU_FAN header, one CPU_OPT header, two CHASSIS headers, one WATER PUMP HEADER.

Currently all of the headers are utilized by three-pin fans. I would like to add three more fans to my setup to obtain the most optimal cooling but there are no empty slots. I tried to use a PWM fan hub that connects to the power supply and motherboard, but it was unable to control the fan speed of my three-pin fans (they remained max). Now I am thinking about getting three fan splitter cables and plugging one into each header to allow two fans each.

Is this safe? My rear fan is the basic cooler master fan and its plugged into the CPU-OPT slot. The CPU fan came with my Cooler Master Hyper 212 Evo.

I wanted to use splitters in the water_pump header and the two chassis headers. All my fans are the bitfenix spectre pro 120mm (red led).

First and foremost, is this safe? Also, will I be able to control the fan speeds (of the pair, not individual fans).

 

[Paperdoc]

As long as you use the common case ventilation fan type, it is totally safe. Typically they use max 0.2 amps or 2.5W. The exception is when you start using super high volume fans that use power like 10W each, and you have to look hard to find those.

Virtually all normal mobo SYS_FAN or CHA_FAN headers can support up to 1 amp total load per header. An old rule of thumb was that you could always be safe using a splitter to put two fans on a header. Many people now advise even three or four is safe.

Now, I disagree with the details of your plan, and here's why. The Water Pump Header very likely does not exercise ANY control of its pump or fan - its purpose is only to provide a steady 12 VDC supply to a water pump. The control of any fan connected to the CPU_FAN or the CPU_OPT header is based on the temperature measured inside the CPU chip itself, and is ideal for cooling the CPU. But control of case ventilation fans is best done using your CHA_FAN headers because they are based on a different temperature sensor built into the mobo by its maker.

So, I advise you to buy two fan splitters with three output arms each instead of just two, and thus connect six fans in total to two CHA_FAN headers. An example:

http://www.newegg.com/Product/Product.aspx?Item=N82E16812423162&cm_re=3-pin_fan_splitter-_-12-423-162-_-Product

That's actually designed for 4-pin fans, but you can use them with your 3-pin fans - the fans simply will not connect to the 4th pin in the outputs.

THEN you need to go into BIOS Setup. See Section 2.2.3 on p. 2-7 of your manual. For each CHA_FAN header select that header, then click on the upper right to choose the DC Mode instead of the PWM Mode. At the bottom, click the Apply box. When done, remember to SAVE and EXIT. This will set your CHA_FAN headers to feed your 3-pin fans with the varying voltage they need to be under mobo control.

 

[Arkeus]

As long as you use the common case ventilation fan type, it is totally safe. Typically they use max 0.2 amps or 2.5W. The exception is when you start using super high volume fans that use power like 10W each, and you have to look hard to find those.

Virtually all normal mobo SYS_FAN or CHA_FAN headers can support up to 1 amp total load per header. An old rule of thumb was that you could always be safe using a splitter to put two fans on a header. Many people now advise even three or four is safe.

Now, I disagree with the details of your plan, and here's why. The Water Pump Header very likely does not exercise ANY control of its pump or fan - its purpose is only to provide a steady 12 VDC supply to a water pump. The control of any fan connected to the CPU_FAN or the CPU_OPT header is based on the temperature measured inside the CPU chip itself, and is ideal for cooling the CPU. But control of case ventilation fans is best done using your CHA_FAN headers because they are based on a different temperature sensor built into the mobo by its maker.

So, I advise you to buy two fan splitters with three output arms each instead of just two, and thus connect six fans in total to two CHA_FAN headers. An example:

http://www.newegg.com/Product/Product.aspx?Item=N82E16812423162&cm_re=3-pin_fan_splitter-_-12-423-162-_-Product

That's actually designed for 4-pin fans, but you can use them with your 3-pin fans - the fans simply will not connect to the 4th pin in the outputs.

THEN you need to go into BIOS Setup. See Section 2.2.3 on p. 2-7 of your manual. For each CHA_FAN header select that header, then click on the upper right to choose the DC Mode instead of the PWM Mode. At the bottom, click the Apply box. When done, remember to SAVE and EXIT. This will set your CHA_FAN headers to feed your 3-pin fans with the varying voltage they need to be under mobo control.

For the water pump header, I currently have a 3-pin fan connected and I am able to control the fan speed from Fan Xpert 3.

As for using fan splitters, can i control the fan speeds for 3-pin fans?

Also I did not use DC mode for my fan hub, could that be the solution? Edit -- Did not work.

Thanks.

 

[Paperdoc]

OK, so the water pump header does exert control. However, IF that control is automatic, I would bet that control is based on the CPU internal temperature, not the mobo temperature.


When you connect two or three fans together to a single mobo CHA_FAN header, they all get exactly the same signal, and hence they all change their speeds under mobo control. However, there is a detail you need to understand. With a single fan on a mobo header, the fan sends back to that header its speed signal (on Pin #3) so the mobo can measure and display the speed. It does not actually use that signal for fan control. BUT it does use it for fan failure monitoring. If the fan stops sending a signal (or, on many mobos, if the indicated speed is below some user-set threshold value), the mobo sends out an alarm so you can get the problem fixed early. Now the mobo circuits that do that can only deal with a speed signal (a series of 2 pulses per fan revolution) from ONE fan. So, any decent fan splitter will send back to the mobo the speed signal of only ONE of its fans, and ignore the rest. This does not affect speed control. But it does mean that you can "see" the speed of only that one fan on that mobo header, and the others are not available. Also, since the others are not being monitored, it is up to you to check periodically to ensure that ALL the fans are still working.

If you use a true 4-pin Fan Hub to connect several fans to a true 4-pin mobo header operating in PWM Mode, the Hub sends the PWM signal from the mobo header to all its fans. A PWM (4-pin) fan must use that signal internally to modify the DC voltage supplied on Pin #2 for speed control. But when you plug a 3-pin fan into such a Hub, that fan has no way to use the PWM signal and so it never modifies the supply voltage. For a 4-pin fan system, the voltage on Pin #2 is always 12 VDC, so a 3-pin fan just runs constantly at full speed. A second important point with a true 4-pin fan hub is that it has a connecti0on line to a fixed 12 VDC power output from the PSU (either a 4-pin Molex connector or a SATA power connector). It uses THAT power source for all its fans, and NO power from the mobo header, thus avoiding overloading the mobo header with too many fans. When you set the header to DC Mode in BIOS Setup it stops sending out a PWM signal, and it starts changing the supply voltage on Pin #2 to variable DC for 3-pin fans. HOWEVER, you had a 4-pin Hub in there, which does NOT use that voltage supply from the mobo header to feed its fans. The fans are still being fed from the PSU connection at a fixed 12 VDC. So, even though you were using 3-pin fans, the Hub prevented the mobo from controlling them.

There really is no 3-pin fan system Hub on the market. (There is one Hub out there that works with a 4-pin mobo Header, NOT 3-pin, but can control both 3- and 4-pin fans.) That is why I recommended three-output SPLITTERS for you. They do NOT have a connection to a fixed DC supply from the PSU, and only send whatever voltage is available from header Pin #2 to all their fans. So when you set the mobo header to DC Mode so it WILL change the voltage on Pin #2, all the SPLITTER's fans get that same voltage to control them.

 

[Arkeus]

OK, so the water pump header does exert control. However, IF that control is automatic, I would bet that control is based on the CPU internal temperature, not the mobo temperature.


When you connect two or three fans together to a single mobo CHA_FAN header, they all get exactly the same signal, and hence they all change their speeds under mobo control. However, there is a detail you need to understand. With a single fan on a mobo header, the fan sends back to that header its speed signal (on Pin #3) so the mobo can measure and display the speed. It does not actually use that signal for fan control. BUT it does use it for fan failure monitoring. If the fan stops sending a signal (or, on many mobos, if the indicated speed is below some user-set threshold value), the mobo sends out an alarm so you can get the problem fixed early. Now the mobo circuits that do that can only deal with a speed signal (a series of 2 pulses per fan revolution) from ONE fan. So, any decent fan splitter will send back to the mobo the speed signal of only ONE of its fans, and ignore the rest. This does not affect speed control. But it does mean that you can "see" the speed of only that one fan on that mobo header, and the others are not available. Also, since the others are not being monitored, it is up to you to check periodically to ensure that ALL the fans are still working.

If you use a true 4-pin Fan Hub to connect several fans to a true 4-pin mobo header operating in PWM Mode, the Hub sends the PWM signal from the mobo header to all its fans. A PWM (4-pin) fan must use that signal internally to modify the DC voltage supplied on Pin #2 for speed control. But when you plug a 3-pin fan into such a Hub, that fan has no way to use the PWM signal and so it never modifies the supply voltage. For a 4-pin fan system, the voltage on Pin #2 is always 12 VDC, so a 3-pin fan just runs constantly at full speed. A second important point with a true 4-pin fan hub is that it has a connecti0on line to a fixed 12 VDC power output from the PSU (either a 4-pin Molex connector or a SATA power connector). It uses THAT power source for all its fans, and NO power from the mobo header, thus avoiding overloading the mobo header with too many fans. When you set the header to DC Mode in BIOS Setup it stops sending out a PWM signal, and it starts changing the supply voltage on Pin #2 to variable DC for 3-pin fans. HOWEVER, you had a 4-pin Hub in there, which does NOT use that voltage supply from the mobo header to feed its fans. The fans are still being fed from the PSU connection at a fixed 12 VDC. So, even though you were using 3-pin fans, the Hub prevented the mobo from controlling them.

There really is no 3-pin fan system Hub on the market. (There is one Hub out there that works with a 4-pin mobo Header, NOT 3-pin, but can control both 3- and 4-pin fans.) That is why I recommended three-output SPLITTERS for you. They do NOT have a connection to a fixed DC supply from the PSU, and only send whatever voltage is available from header Pin #2 to all their fans. So when you set the mobo header to DC Mode so it WILL change the voltage on Pin #2, all the SPLITTER's fans get that same voltage to control them.

I see, well now I have two options, (1) the splitter one you suggested or (2) buy this http://www.newegg.ca/Product/Product.aspx?Item=N82E16813995054.

The fan extension card seems to be supported buy I am not sure if it will work.

 

[Paperdoc]

Your second option still cannot do the job you want. The limit you are working with is that your fans are of the 3-pin design, and hence can ONLY be controlled by a fan header that operates in Voltage Control Mode. Now it happens that the 4-pin CHA_FAN headers on your mobo can be configured in BIOS Setup to work in either PWM Mode or DC Mode (aka Voltage Control Mode), so you CAN make your mobo headers control your 3-pin fans. BUT I cannot find any details on the operation of that special expansion card for your ASUS mobo. It creates three extra 4-pin fan headers that can control 4-pin fans, and MOST likely that is by using PWM Mode which can NOT control 3-pin fans. I can't find any info on whether it is possible somehow to configure this card also to operate in DC Mode rather than PWM Mode.