System Cooling Question

Jayke · 8 Nov 2018 at 03:57

My system components are;

- Gigabyte GA-B85M-D3H
- CoolerMaster Masterliquid Lite 120
- 4 x Corsair AF120 Quiet Edition (3-Pin, 120mm, 1,500RPM)

I am currently downsizing from ATX to Micro-ATX and I have a question in regards to case fans and fan splitters. My motherboard has;

- 3 x SYS_FAN headers.
- 1 x CPU_FAN headers.

The CPU AIO (CM Masterliquid Lite 120) will take up the CPU_FAN header and 1 of the SYS_FAN headers leaving me with 2 SYS_FAN headers to power 4 case fans. To get around this issue I am planning on ordering;

https://www.overclockers.co.uk/ek-water-blocks-ek-cable-splitter-4-fan-pwm-extended-wc-9cq-ek.html

Please correct me if I am wrong in my presumptions, the fans I have are not PWN capable so I am not fussed about automatic fan control however I would like to have the ability to control the speed of the fans via the Gigabyte desktop application. My thought is, as I will be plugging the EK Water Blocks Cable Splitter into one of the SYS_FAN headers (allowing me to control the speed), the 4 fans direct into the splitter and of course the molex connector to power them.

Will this work and will I be ok plugging 3-Pin case fans into the 4-Pin EK Water Blocks splitter? Thanks.

bremen1874 · 8 Nov 2018 at 04:16

I think if you use that cable with 3 pin fans they'll all run at full speed.

They'll be getting their power from the molex. The connection to the motherboard only carries the PWM signal and that'll do nothing in this case.

If you're connecting 3 pin fans you should be able to use two basic fan splitters and cable two fans to each motherboard socket. This assumes that the motherboard is capable of speed controlling 3 pin fans.

Jayke · 8 Nov 2018 at 04:41

bremen1874 said:
I think if you use that cable with 3 pin fans they'll all run at full speed.

They'll be getting their power from the molex. The connection to the motherboard only carries the PWM signal and that'll do nothing in this case.

If you're connecting 3 pin fans you should be able to use two basic fan splitters and cable two fans to each motherboard socket. This assumes that the motherboard is capable of speed controlling 3 pin fans.

I see what you're saying, I presumed that because I had a cable plugged into a SYS_FAN header it would be controllable despite the fans being powered by the Molex connector. I am best off just buying a Molex to 4 fan splitter as thats two less cables plugged into the motherboard stretching across the entire build which I wanted to avoid. I will just have to deal with the case fans running at full speed which is not that big of an issue anyway, the fans I have are very quiet regardless.

Thanks for your help.

doyll · 8 Nov 2018 at 12:33

What bremen1874 said.

That splitter is for PWM fans (as it's name says) so power is constant 12v with PWM control on pin-4 having the PWM circuitry in fan pulse that 12v to control fan speed.

Your Corsair AF120 Quiet Edition fans have only a 0.75mm H2O static pressure rating at full speed or 0.5 at about 1100rpm. This low rating is about 1/3-1/2 what case fans need to be rated to be able to move needed airflow. You need better fans. Hopefully you can return the ones you have and get better ones. If you can we can suggest better fans like Phanteks PH-F120MP or PH-F140MP. PH-F120MP are on special in 2-pack for £14..99 and 3-pack for £26.00 but there are only a couple in stock so hurry. They are PWM too so that splitter will work on them if your motheboard has PWM headers.

Does your motherboard manual say fan headers are PWM or variable voltage? Pin-2 on fan headers in manual needs to be labeled '12v' and pin-4 needs to be labeled 'PWM' or 'control' for it to be a PWM fan header. For variable control pin-2 needs to be labeled 'variable voltage' or 'control'

Jayke · 9 Nov 2018 at 03:30

doyll said:
What bremen1874 said.

That splitter is for PWM fans (as it's name says) so power is constant 12v with PWM control on pin-4 having the PWM circuitry in fan pulse that 12v to control fan speed.

Your Corsair AF120 Quiet Edition fans have only a 0.75mm H2O static pressure rating at full speed or 0.5 at about 1100rpm. This low rating is about 1/3-1/2 what case fans need to be rated to be able to move needed airflow. You need better fans. Hopefully you can return the ones you have and get better ones. If you can we can suggest better fans like Phanteks PH-F120MP or PH-F140MP. PH-F120MP are on special in 2-pack for £14..99 and 3-pack for £26.00 but there are only a couple in stock so hurry. They are PWM too so that splitter will work on them if your motheboard has PWM headers.

Does your motherboard manual say fan headers are PWM or variable voltage? Pin-2 on fan headers in manual needs to be labeled '12v' and pin-4 needs to be labeled 'PWM' or 'control' for it to be a PWM fan header. For variable control pin-2 needs to be labeled 'variable voltage' or 'control'

Thanks for your reply, I got a really good deal on these fans £20 for 2 duel packs so I am going to at least check my temps as I cannot find any horrific reviews? Amazon, ******, Scan everybody is happy with them. My MB I need to check what Rev I have I think 2.0 has PWM but 1.0 does not, so I am going to just plug the 4 fans into a splitter then into Molex, see how it sounds and if I want I will just buy 2 SYS_FAN splitters later down the line so I can control the speed if needs be.

According to the manual, Rev 1001 which I can only presume as Rev 1.0, here is what it says for System Fans;

doyll · 9 Nov 2018 at 11:31

Jayke said:
Thanks for your reply, I got a really good deal on these fans £20 for 2 duel packs so I am going to at least check my temps as I cannot find any horrific reviews? Amazon, ******, Scan everybody is happy with them. My MB I need to check what Rev I have I think 2.0 has PWM but 1.0 does not, so I am going to just plug the 4 fans into a splitter then into Molex, see how it sounds and if I want I will just buy 2 SYS_FAN splitters later down the line so I can control the speed if needs be.

According to the manual, Rev 1001 which I can only presume as Rev 1.0, here is what it says for System Fans;

Trying to get case airflow with those fans is a total waste of time. They simply do not have the ability to overcome normal case grill and filter resistance, not even enough for grill resistance. Anybody saying they are happy with Corsair AF120 don't know what a real fan can do. Sorry to be so blunt, but that's the truth.

CPU fan header is PWM because pin-4 is 'speed control' Sys fan headers are variable voltage becuase 'VCC' means that pin/lead is doing nothing on that header.

Jayke · 10 Nov 2018 at 21:53

doyll said:
Trying to get case airflow with those fans is a total waste of time. They simply do not have the ability to overcome normal case grill and filter resistance, not even enough for grill resistance. Anybody saying they are happy with Corsair AF120 don't know what a real fan can do. Sorry to be so blunt, but that's the truth.

CPU fan header is PWM because pin-4 is 'speed control' Sys fan headers are variable voltage becuase 'VCC' means that pin/lead is doing nothing on that header.

I appreciate your advice and truthful, to the point answers are what I like. Nobody has time to beat around the bush unless you're living on the land of lesbiana.

On the SYS_FANS, what is pin 2 doing "+12v /Speed Control"... Are my SYS_FANS capable of using PWM, if they are I will buy 4 PWM fans using a splitter in both SYS_FAN 2/3 to power the 4. If not, I will buy non PWM fans with higher static pressure and simply power them via Molex.

doyll · 11 Nov 2018 at 12:06

Jayke said:
I appreciate your advice and truthful, to the point answers are what I like. Nobody has time to beat around the bush unless you're living on the land of lesbiana.

On the SYS_FANS, what is pin 2 doing "+12v /Speed Control"... Are my SYS_FANS capable of using PWM, if they are I will buy 4 PWM fans using a splitter in both SYS_FAN 2/3 to power the 4. If not, I will buy non PWM fans with higher static pressure and simply power them via Molex.

Pin-2 is power to fans on all fan headers.
Pin-1 = ground
pin-2 = power ('12v' = PWM header, 'speed control' = variable voltage header)
pin-3 = rpm signal from fan
pin-4 = PWM/speed control= PWM, anything else = variable voltage

You do not say what pin-4 is on SYS FANS where pin-2 is '+12/Speed Control', so I'm going to guess that fan headers with '+12v / Speed Control' can be set in bios to either '12v' or 'Speed Control' because '12v' is what PWM control uses and 'Speed Control' is usually variable voltage which is what 3-pin fans use to their control speed.

All PWM fans I know of perform normally on variable voltage. If a PWM fan does not receive a PWM signal/speed control signal on pin-4 the motor is receiving constant power on pin-2 and if it's variable voltage on pin-2 that power lower voltage for lower rpm and higher voltage for higher rpm.

As I said before if pin-2 is 12v and pin-4 is 'PWM' or 'speed control' the header is PWM controlled.

As I said before, AF120 fans have such low static pressure (0.74mm H2O) they cannot overcome case grill and filter resistance. Grill and filter generate approx 0.4-0.5mm H2O of resistance (it varies depending on how much air is flowing) As I said before, static pressure rating is the maximum pressure the generated when fan is mounted to a sealed box and ran at full speed. So when I say a grill and filter are about 0.4-0.5mm H2O it's not really a measurement of filter and grill resistance, but fans with low static pressure cannot push hard enough against the grill and filter to overcome their resistance and move needed volume of air through the case.

As I said before, you need fans with 1.3-1.5mm H2O static pressure rating for fans to be able to overcome resistance of grill and filter and flow needed air to keep components nice and cool under load. As I said before, Ph-F140MP and PH-F120MP are very good fans and very reasonably priced.