Case fans, plug into Mobo or PSU

Toggle sidebar Toggle sidebar
F

FryedPigBacon

Commendable
Apr 2, 2016
25
0
1,530
This is my first build and some of this may seem stupid but I'm super new, kinda just jumped in. I'm using the thermaltake v21 as my case, it has 1 case fan in the front, a 200mm.

I figured it would be good if although maybe not entirely needed to add a exhaust fan, 120 or 140mm.(not yet purchased) I'm planning on using a I5 6500 and its stock cooler.

So now my question is I have 3 fans tota, CPU fan which I intend to plug into the cpu fan header.
Then i have the 200m fan and the yet to be purchased 120/40 case fan. My mobo (gigabyte GA-H110M-A) only has one system fan header.

Initially i thought to just plug one fan jnto the header and the other into my PSU (EVGA SUPERNOVA 650 GS 80 PLUS). In this scenario which fan is better to plug into the psu? Because if I am not mistaken the fan will run full speed all the time which doesn't bother me assuming its not super loud. But will the fan burn out that much quicker?

Also read I could get a fan controller and plug that into the header and the fans into the controller which would allow the fans to be controlled but has to be pwm fan. I am however unclear if its the mobo controlling them or I would have to get software. I know that somewhere in this option I'm not understanding it all correctly.

Tldr - which options are best for adding a case fan with only 2 mobo headers.

 
Solution
P
ALERT! Change of info!

I find the info and labels of the manual for your mobo confusing because it does not use the same terms as most do in describing the fan ports. For that reason I said I believe your only SYS_FAN port is really a 3-pin port even though it has 4 pins.

In another forum very recently I've run across another model of Gigabyte mobo that uses the same labels and terms. BUT it also had additional information about configuring its SYS_FAN port that indicates strongly that it IS a real 4-pin fan port operating in PWM Mode. If that is the case, you cannot control any 3-pin fan from it. You would have to use 4-pin fans. That also would leave you unable to control the speed of the pre-installed 200mm front case fan. So my...
Sort by date Sort by votes
Robert Cook

Robert Cook

Expert
Ambassador
Dec 15, 2014
6,113
0
21,960
if the fans are not high amperage, just buy a cheap three way splitter cable. then you can control all three ( they will all run at the same speed setting as the fan header). running them off the PSU is fine too, obviously they will run at full speed, but that will not limit their life span, fans are meant to spin.
 
Upvote 0 Downvote
F

FryedPigBacon

Commendable
Apr 2, 2016
25
0
1,530
Okay, if all three are plugged into a splitter does is matter which header it is plugged into? System vs cpu?

I'll have to find the amerage on the built in case fan. Is what constitutes high voltage determined by what the mobo can handle?
 
Upvote 0 Downvote
P

Paperdoc

Polypheme
Ambassador
Oct 19, 2006
11,280
1,035
69,340
I think a splitter can work for you. Generally speaking, you can power 2 fans (using a Y-splitter) from one fan port, but not more. The "tricky" part is whether the fans you have match the mobo fan port type.

As nearly as I can tell from the Thermaltake website, the fan included in your case is a 3-pin type which can ONLY be controlled by a system operating in Voltage Control Mode. This normally includes 3-pin fan headers on a mobo (but not 4-pin) and many third-party controllers. HOWEVER, when I look at your mobo's manual it says that the only mobo fan port has 4 pins, BUT the pinout diagram labels these as if the port really operates as a 3-pin port in Voltage Control Mode. So, that fan should work under control by your mobo port.

Now, to add a fan, you MUST get two things: a 3-pin fan (NOT 4-pin!) and a 3-pin Y-splitter. This will allow you to connect both fans to the only mobo SYS_FAN port you have. That is the correct way to control case ventilation. CPU cooling is done separately and, as you plan, you should connect your CPU cooling fan to the CPU_FAN header. You do NOT need a splitter with three outputs because you only plan 2 case fans, and putting 3 fans on one SYS_FAN port might overload it.

Powering your two case ventilation fans from the mobo port will allow it to control those fans' speeds according to heat generated by workload. When your system is doing little work the interior temperature will drop, and the control system can slow the fans down. Heavier work will result in higher cooling by increased fan speed, and it's all automatic. Any third-party fan controller you use does NOT do automatic control - they leave it up to you to decide how much cooling is needed. And as you realize, connecting the fan(s) directly to a PSU output means they can only run at full speed all the time.
 
Upvote 0 Downvote
F

FryedPigBacon

Commendable
Apr 2, 2016
25
0
1,530
When I look on the actual mobo the headers have 4 pins, the manual i downloaded from the website also shows 4 pin on the diagram.
But the system header pins are
1: GND
2: Speed control
3: Sense
4: VCC

So 4pin Fan will not work because the 4th pin on the fan is pwm? But what the hell is this VCC pin for on the mobo header?

And lastly I have a 4 pin splitter already from a friend, this will not work at all? Or will it work in voltage control mode if a 3 pin fan is plugged in?

 
Upvote 0 Downvote
P

Paperdoc

Polypheme
Ambassador
Oct 19, 2006
11,280
1,035
69,340
If you look at the pinout for the 4-pin CPU_FAN header, it shows Ground, +12 VDC, Sense and Speed Control, which is different from the labels on the SYS_FAN port.

The CPU_FAN port IS a true PWM Mode (4-pin) port that supplies a constant 12 VDC to the motor on Pin #2 and the PWM signal on Pin #4. A circuit inside the motor case on a board uses the PWM signal to modify the flow of current from the 12VDC supply line through the motor windings, thus achieving speed control.

For the SYS_FAN port, on the other hand, I read those labels to mean that its Pin #2 has a VARIABLE DC voltage, not a fixed 12VDC, and that's how it controls fan speed. That is exactly how a standard 3-pin fan port operating in Voltage Control Mode works. The fact that its Pin #4 does NOT show as any kind of control signal confirms to me that it is NOT a PWM signal.

With a SYS_FAN port operating only in Voltage Control Mode, any 3-pin fan connected there will operate exactly as it should under mobo control. Moreover, it you plug a 4-pin fan in there, it also works under speed control by the mobo. This is part of the backwards compatibility aspect of the design of the new 4-pin fans. When connected to such a port it has NO PWM signal to use to modify the voltage supplied on Pin #2, so it just does whatever that voltage allows, and acts like a 3-pin fan.

If you have a 4-pin Y-splitter already, go ahead and use it with your 3-pin fans. It will merely split the signals from that SYS_FAN port between the two fans, and those signals really are just 3-pin port signals anyway.

By the way, background: for compatibility in design, a 4-pin fan's signals are exactly the same as those of a 3-pin for two of the pins. Pin #1 is Ground in both, and Pin #3 in both it the speed pulse signal being sent back to the mono. Pin #2 is a variable DC supply voltage on a 3-pin system, but a fixed +12VDC on a 4-pin system. Then of course Pin #4 (on a true 4-pin system), which does not exist on a 3-pin system, provides the PWM signal for a 4-pin fan to use. It happens that your mobo does NOT do this exactly on its SYS_FAN port - it uses a "fake" 4-pin port that actually WILL control either a 3-pin or a 4-pin fan because of compatibility factors in the 4-pin fan's design.

If you follow those differences in detail, you can understand why the one problem in all this mix of 3- and 4-pin fan systems comes up when you plug a 3-pin fan into a true 4-pin port operating in PWM Mode. (You do NOT have this problem!) That fan will be supplied on Pin #2 with a constant 12 VDC, and it cannot use a PWM signal (it does not even have a wire for Pin #4 anyway) because it does not have the special circuit, so it can only run at full speed all the time.
 
Upvote 0 Downvote
P

Paperdoc

Polypheme
Ambassador
Oct 19, 2006
11,280
1,035
69,340
ALERT! Change of info!

I find the info and labels of the manual for your mobo confusing because it does not use the same terms as most do in describing the fan ports. For that reason I said I believe your only SYS_FAN port is really a 3-pin port even though it has 4 pins.

In another forum very recently I've run across another model of Gigabyte mobo that uses the same labels and terms. BUT it also had additional information about configuring its SYS_FAN port that indicates strongly that it IS a real 4-pin fan port operating in PWM Mode. If that is the case, you cannot control any 3-pin fan from it. You would have to use 4-pin fans. That also would leave you unable to control the speed of the pre-installed 200mm front case fan. So my previous advice may be wrong.

How to check it out? Well, plug that front 3-pin fan into the mobo SYS_FAN port if it is not already. We want to see whether or not that fan's speed can be changed by the port. Boot up directly into BIOS Setup and go to the MIT tab, select PC Health Status. See your manual, p. 23.

Under the System Fan Speed Control heading set that to Manual. That allows you to set a value for Fan Speed Percentage. Try out different values for this, observing what the effect is on the speed of that front fan. If its speed changes, then the port is succeeding in controlling fan speed, and you can buy a second fan and Y-splitter of the same type as the current front fan. BUT if the front fan just keeps on running at full speed all the time AND that fan really has only 3 wires from it to its female connector, then your SYS_FAN port is a true 4-pin port operating in PWM Mode (as I now suspect) and you must use 4-speed fans to be able to control them with this port.

So, what options do you have IF the port is truly 4-pin and you have a 3-pin front fan that only runs full speed?
1. Buy a 4-pin fan Y-splitter (you already have one?) and a new 4-pin rear fan. Connect both fans to the splitter. I suggest you look closely at the splitter outputs and use the one that has all 4 pins to plug in the new 4-pin fan. That way you'll be able to display that fan's speed. The older 3-pin fan will always run at full speed, so you don't really need to measure that.
2. Buy two new 4-pin fans, one each for front and rear. Replace the pre-installed 3-pin fan at the front with a 4-pin one. Use the Y-splitter to connect both fans to the SYS_FAN port and it will control the speed of both at the same time.
3. (This may be more expensive). Buy a particular 4-pin fan hub called the Phanteks PWM Hub, and one 3-pin fan for the rear. That Hub gets its power from a SATA power output directly from the PSU and has a female 4-pin fan connector on wires to plug into your mobo's 4-pin SYS_FAN port to pick up its PWM signal. Then it has six 3-pin outputs on it for fans, and actually (because of a design feature of 4-pin fans) it can control any mix of 3-pin and 4-pin fans plugged into its ports. How? Apparently, rather than merely sharing the PWM signal to all its fans as many simple hubs do, it creates its own group of true 3-pin fan ports operating in Voltage Control Mode. Remember to plug one of your fans into its white Port #1 - that is the only port of the Hub that returns a fan speed signal to the mobo port.
 
Upvote 0 Downvote
Solution
F

FryedPigBacon

Commendable
Apr 2, 2016
25
0
1,530
Ok, I agree that the mobo manual is not particularly clear. We are going to build the computer tonight and we will have to test out what happens with the front fan to get a concrete answer on what sort of header it is. But I had also found on a gigabyte forum where someone said that if the 4th pin shows VCC or reversed then it is a "fake" 4pin. I think that because the second pin shows speed control it can operate in voltage control.

This answer however was from 2014. Anyways thanks for the help I'll report back what I find..
 
Upvote 0 Downvote
You must log in or register to reply here.

TRENDING THREADS

Latest posts

Moderators online

Share this page

COMPANY
RESOURCES
FOLLOW
Top Bottom