Connecting 2x3pin SP fans to 4 pin CPU header (voltage control/RPM reading)

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hbomb79

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Upgrading computer in a month or two, just trying to finalise the parts. A big question that I have is how to connect fans correctly to my motherboard.

My upgrade plan
My motherboard has a 4pin CPU header, a 4pin 'water cooling CPU fan header' and 2x system fan headers and 1x 'system fan/water cooling pump header'.

My plan is to upgrade my CPU to a i7-7700k with an AIO water cooler (dual radiator, see here). I am also purchasing a new case to put all of this in to.

The case comes with 3 fans (I don't know the pin connector type). I am planning on replacing these fans with Corsair AF140 (3pin). I am also planning on replacing the fans of the AIO radiator with Corsair SP120 (3pin). I won't be upgrading the fans for a little while however, so the solution needs to work with both 3pin and 4pin fans (The AIO stock fans are 4 pin fan connectors).

The Problem
I need to find a way to connect these 5 fans (3 [unknown pin type] from case, 2 [4 pin] from AIO cooler) to the motherboard. While I could connect these fans to the PSU, I would much rather them run via voltage control (especially the AIO radiator fans). My question is what equipment do I need, and how exactly would I setup it up so that all 5 fans are connected to the motherboard and are voltage/PWM controlled?

My plan was to buy a fan Y splitter to connect the two AIO radiator fans to the CPU_FAN header, and then use another Y splitter to connect the 3 case fans (Connecting one case fan directly to the motherboard, and the other two via the Y splitter). How will this work in terms of RPM monitoring of the CPU fans (If I understand correctly, I need to cut one of the wires on the Y-splitter so only one fan is reporting it's RPM?), and voltage control of the case and CPU fans.

It may be worth noting that I have a CPU_OPT fan header. I wonder if this could be used for the second radiator fan instead of a Y-splitter, allowing RPM management of both fans instead of only one? The AIO radiator fans will be replaced with 3 pin fans eventually. If I connect the stock fans to the CPU and CPU_OPT headers, will the 3pin fans receive voltage control from the motherboard. I assume the board provides voltage control to all fan headers, but I don't know how to find out.

Sorry if I rambled, I am brand new to this and have no elegant way of presenting my ideas.
 
Solution
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Did not see the mobo info listed. Thanks for that.

Your mobo has 5 fan headers in total. ALL of them are "Hybrid", meaning they each can be set in BIOS Setup to do either PWM or Voltage Control. Moreover, they all claim to have an "Auto" setting which is supposed to test the fan connected and set itself to the correct mode. I'm not sure how that works and whether you can depend upon it, so my own preference is to manually set the correct mode for each header in BIOS Setup. Your choice on that.

Your mobo also has a total of six temperature sensors (including the one built into the CPU chip) and the ability in BIOS Setup to set, for each header separately, which sensor will be used for control of that header's fans. Well, one exception...
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Paperdoc

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Neither of the items linked above will do what you want. The first is a third-party fan controller that includes its own temperature sensor and can perform automatic fan speed control based on that sensor. Your challenges there are: where do you place the sensor, what is the correct target temperature at that spot, and how do you keep it fixed to that sampling location? This unit can NOT access or use the temperature sensor built into the mobo, or the settings the mobo would use. You could use it for the case ventilation fans only (not the CPU cooler system) under those limitations.

The second item is a 4-pin Fan Hub. It ONLY works when your mobo header is actually using PWM Mode for controlling its fans, and it ONLY works with 4-pin fans. You plan to have all 3-pin fans, so it cannot do your job.

Let's separate the CPU cooling and the case cooling for ease. That radiator comes with two 4-pin fans PLUS a small 4-pin fan Splitter (unknown make) with 4 output ports that looks exactly like the DeepCool model shown here

https://www.newegg.com/Product/Product.aspx?Item=9SIA4RE4P85586&cm_re=fan_splitter-_-1W7-001E-00001-_-Product

This is a true Splitter that can do that job for either 4-pin fans or 3-pin fans (although mixing types on this would not work exactly as you might wish). This is important because to connect more than one fan of the 3-pin design to a mobo header you MUST use a Splitter AND the mobo header MUST use Voltage Control Mode (aka DC Mode). To help with what you need to do now and later, here's an example of a simple Splitter with only 2 output arms

https://www.newegg.com/Product/Product.aspx?Item=N82E16812423160&cm_re=4-pin_Splitter-_-12-423-160-_-Product

Note that this Splitter, UNlike a HUB, does NOT have an extra arm that plugs into a power output connector from the PSU.

NOTE for both these Splitters that you do NOT need to snip off any wires. The snip process is just to ensure that the speed signal from only ONE of the Splitter's output fans is sent back to the mobo. Both of these Splitters have that feature built into their design (one one of the output arms contains the Pin #3) so they do NOT need any modification.

So, how to use? Start with the CPU cooler system. It comes with two 4-pin fans and that 4-port Splitter. Its manual says you plug the AIO system's pump unit into CPU_FAN1 and the Splitter into CPU_FAN2. VERY likely on your mobo that second one is the CPU_OPT header. Now, this is two fans. So, I suggest you get a simple 2-output 4-pin fan Splitter like I linked above and use that for this job, reserving the 4-output Splitter for use with your case fans. You have not specified exactly what mobo you will be using. But almost all today allow you options in BIOS Setup for all the CPU fan headers to specify whether they use PWM Mode or Voltage Control Mode (aka DC Mode), and that option is done separately for the two CPU_FAN headers. So, when you first set up your system using the supplied 4-pin fans on the radiator, configure the CPU_OPT header (where you connect those fans via a 2-output Splitter) to use PWM Mode. The manual does NOT make this next point clear, but even though the pump unit has only 3 pins on its connector, I suspect you are supposed to set its header (CPU_FAN) also to PWM Mode. Set this way, it will run the pump unit at full speed all the time, and actual control of the CPU temperature will be done by varying the speed of the two fans on the radiator.

LATER when you change those fans to SP120 3-pin units, re-configure the CPU_OPT header to use Voltage Control Mode (aka DC Mode).

Now on to the case ventilation fans. VERY likely the three fans included in the case are of the 3-pin design, and you will at some time replace them with a different 3-pin model. So on that point making the change will be easy. You can always plug 3-pin fans into 4-pin fan ports, so you can use that 4-output Splitter that came with your CPU cooler to connect these three case fans to one mobo CHA_FAN header. The loose unanswered question here, though, is whether your mobo's CHA_FAN headers can be set to use Voltage Control Mode. Some can, some already do that, and some cannot. To make sure, post back here the exact make and model number of your mobo so we can look up that detail and advise.

 
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hbomb79

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Thank you for your response. I am still trying to absorb all the information.

I have included the exact motherboard in the OP post, although here it is again if it helps explain configuration: https://www.gigabyte.com/Motherboard/GA-Z270X-Gaming-K5-rev-10#kf

Edit: It seems the 4fan splitter included with AIO cooler is the one you linked (same brand as the cooler and looks identical in videos). Judging by the motherboard fan headers I believe I can plug all three fans into the motherboard without the use of any splitter, is this correct?

For ease, motherboard fan specifications taken from manual (all fan headers a 4 pin 'hybrid' fan headers according to the manual and website):

1 x CPU fan header
1 x water cooling CPU fan header
2 x system fan headers
1 x system fan/water cooling pump header

I assume I plug the AIO pump into the CPU fan header, (CPU_FAN) and the splitter into the 'water cooling CPU fan header' (I assume this is CPU_OPT on the motherboard). Or is it the other way around?

I would then insert the three fans into the remaining system fan headers.

All good?
 
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Paperdoc

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Did not see the mobo info listed. Thanks for that.

Your mobo has 5 fan headers in total. ALL of them are "Hybrid", meaning they each can be set in BIOS Setup to do either PWM or Voltage Control. Moreover, they all claim to have an "Auto" setting which is supposed to test the fan connected and set itself to the correct mode. I'm not sure how that works and whether you can depend upon it, so my own preference is to manually set the correct mode for each header in BIOS Setup. Your choice on that.

Your mobo also has a total of six temperature sensors (including the one built into the CPU chip) and the ability in BIOS Setup to set, for each header separately, which sensor will be used for control of that header's fans. Well, one exception: the CPU_FAN header is fixed (I believe) to use only the temperature sensor in the CPU chip, which makes sense. BUT that means that the actual device that is used to control the CPU's temperature - in your case, the pair of cooling fans on the radiator - REALLY need to be connected to that fan header using a Splitter. If you have faith in the "Auto" mode setting, use that. Then, assuming it does its job, when you make your change from 4-pin to 3-pin fans there later, the mobo will detect that and make its own adjustment. IF it does not, what will happen is that those fans will run at full speed all the time. Of you see that, go into BIOS Setup and manually change the configuration of that one header to use Voltage Control.

See the manual p. 29 for the settings available in BIOS Setup for your fan headers. Generally ensure that ALL of them are set to use "Normal" fan speed control - that is, use the mobo's automatic control system. For Fan / Pump Control Mode. You can let it use "Auto" if you wish, or manually set to "Voltage" for headers that power 3-pin fans, or to "PWM" for headers that power 4-pin fans.

I suggest you plug the pump unit of your CPU cooler AIO system into the CPU_OPT header. Referring to p. 29, set the Fan Control Use Temperature Input item to the CPU internal sensor. Here I really suggest you consult the manufacturer's Tech Support for that DEEPCOOL Gamer Storm Captain 240EX AIO Liquid Cooling cooler system. The question I can't answer from their website info is exactly what the pump unit needs for power. It has a 3-pin connector, which likely means it acts like a 3-pin fan in many ways. If you connect that to the CPU_OPT header and leave it in "Auto"mode, the mobo may well decide it is a 3-pin fan and use Voltage Control Mode to change its speed. HOWEVER, some AIO pump systems do not want that - they want a fixed full 12 VDC supplied to the pump via its Pin #2 so that it always runs full speed, and they achieve temperature control of the PCU by changing only the speed of the radiator fans. IF that is what the DeepCool Gamer Storm system needs, you can do it one of two ways. One (I recommend this way) is to configure its pump header to use "Full Speed" Speed Control. The alternative is to set it to "PWM" mode, because a 3-pin fan on a 4-pin header will always run full speed.

Now, for the three 3-pin case fans (originals or your later changes), you still have three mobo fan headers available. Each of them is fully configurable, so you CAN do this with one fan per header and not need any Splitter for these three fans. (That means the Splitter already supplied with the AIO cooler system can be used for its radiator fans.) For this, use the SYS_FAN1, SYS_FAN2 and SYS_FAN3/Pump headers. In each case, set the header's Fan Speed Control to "Normal", its Fan Control Use Temperature Input to a general Motherboard sensor, and the Fan / Pump Control Mode to either "Auto" or "Voltage". Now, the fact is that there really are 5 temperature sensors on this mobo you could choose for each of these three case ventilation fans, and I don't know exactly which is ideal. If there's confusion, ask Gigabyte Tech Support which sensor is best for your case vent fans.
 
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hbomb79

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Thanks for such in-depth information -- Makes this so much easier to understand.

One thing I am still uncertain about is, as you mentioned whether or not the pump should be running at 100%. Unless I can find out, I will run it at 100%, just to be safe (I have heard stories linked to the pumps shutting down and starting up again while using the PC, causing the pumps to fail).

One other thing, should I be concerned about the pump power draw. I assume that the CPU_OPT (where I attach the pump) can handle the power draw as it is marked as a 'Fan/Water pump pin header' on the motherboard diagram (on their website), is the power draw an issue in your eyes, or do you agree that it can handle the pump draw?
 
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Paperdoc

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Power draws for the CPU cooler AIO system will be no concern at all. Any common fan header can supply 12 VDC max at a current up to 1.0 amps. (I think I read twice that for your mobo's headers, but it does not matter.) The specs for your cooler system say the fans draw 0.12 amps (I'm presuming, each), and the pump unit draws 0.16 amps. Both are VERY much less that the max limits, so don't worry.

I am inclined also to assume the pump needs to run full speed using a 12 VDC fixed supply, but I am interested to know what Deepcool has to say. I see the issue from two perspectives. One is that any DC motor (fan, pump, or whatever) has a minimum voltage required to start it up from a stopped condition, and also a minimum voltage required to prevent it from stalling once it is running. For most computer fans the safe minimum voltage seems to be about 5 VDC, and a fan given a lower voltage while running MAY stall. If it does, then the voltage must be raised a fair amount - at least to 7 VDC, preferably hjgher - to re-start it. Now, what those particular voltages are for a PUMP motor I don't know. Moreover, the risk of stalling increases a little as the motor gets older and its bearings wear. So having the mobo supply to the pump motor reduced voltages just as it would do for a fan does risk stalling and a significant delay in re-starting. That would be very bad for a CPU chip cooling system.

Secondly, the way an automatic cooling control system (as operated by your mobo) is "tuned" for optimal performance depends on a number of factors including response times of the many components of the control system and the heat generator (the CPU chip). The default settings for these in the mobo's automatic control system is quite suited to handling fans as the cooling devices, varying their speed to change cooling rates. But if you apply the same varying signal to BOTH the fans on the radiator and to the pump that determines the rate of fluid flow through the radiator, a decrease in signal produces a larger reduction of cooling rate than you'd get from slowing down only the fans. It makes "tuning" the control loop more complicated, so it's much simpler to keep the pump speed (and hence fluid flow rate) stable and manipulate only the fan speeds (heat removal rate from the fluid in the radiator).

Thanks for Best Solution.
 
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hbomb79

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I know this isn't technically part of the topic, but it seems overkill to make a new topic.

If the AIO cooler leaks (I here this is more common than I would like, not sure how true that is) and damages other components, will the warranty cover the damage? I see posts where the manufacturer has replaced GPUs after liquid dripped on them, causing them to break -- not sure if this is common practice for Deepcool (if not, what manufacturers do you know of that do cover consequential damage, it would heavily sway my decision of cooler?).

No problem for best solution, you have helped me a ton!
 
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