Question PWM case fan splitters or hub?

Jan 18, 2022
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Hi there!

MB: Gigabyte Z690 UD AX
Fans: 5x 140mm Be Quiet Light Wings, 1x 120mm Be Quiet Light Wings.

I've installed 6 fans in my case and only have 2 PWM headers on my MB. The fans have splitters attached for daisy chaining but they are on the RGB cable. My first question is if I do daisy chain them then will this affect the PWM control & powering of the fans?

If it will then I'll have to buy some kind of splitters. My local computer shop has said that they have two options:

1. A splitter cable with support for 5 fans and a molex power connector but still plugs into the SYS FAN header on the MB. Will using the power connector mean the fans will not be PWM controlled? If I only use it for 3 fans can I get away without using the power connector?

2. A fan 'hub' which also supports up to 5 fans. They described it as a box with 5 fan ports that plugs into the SYS FAN header.

So, should I go for one of these options or as a 3rd option buy a few regular splitters, without a power connectors, and daisy chain them this way?

My intent on whichever option I choose is to use 3 fans on each of the SYS FAN headers to spread the load evenly. Each header has 2A / 24W ratings and 3 fans are well within these limits, approx 0.32 - 0.39A / 3.85 - 4.56W per fan.

Finally, my MB also has a SYS FAN PUMP header which has the same pin configuration and power ratings as the other SYS FAN headers, would it be viable to use this header to spread the load further? I've not found anything in the manual to suggest either way.

Any help, advice or alternative suggestions welcome.
 

DRagor

Illustrious
The fans have splitters attached for daisy chaining but they are on the RGB cable. My first question is if I do daisy chain them then will this affect the PWM control & powering of the fans?
The way you connect RGB cables has no effect whatsoever on fan motors, They are completely separate circuits.
1. A splitter cable with support for 5 fans and a molex power connector but still plugs into the SYS FAN header on the MB. Will using the power connector mean the fans will not be PWM controlled?
Can't say for sure without knowing the cable, but probably you will still be able to use PWM while using molex for power.
2. A fan 'hub' which also supports up to 5 fans. They described it as a box with 5 fan ports that plugs into the SYS FAN header.
Not a fan of such solution. Mainly because all fans connected to hub will run same speed, and I prefer separate control of front and rear fans (unless you use two of them)
My intent on whichever option I choose is to use 3 fans on each of the SYS FAN headers to spread the load evenly. Each header has 2A
At 2A per header it is perfectly fine to use normal 3 to 1 splitter with those fans.
Finally, my MB also has a SYS FAN PUMP header which has the same pin configuration and power ratings as the other SYS FAN headers, would it be viable to use this header to spread the load further?
No need to do that, unless you want to have three 'zones' of control - for example one header runs all front fans, second runs rear fans, and third runs top fans, giving you more precise control of airflow. Also, many headers designed as PUMP will not have an option for speed control meaning it would run fans connected to it full speed (although afaik all Gigabyte mobos have full control on all headers).
 

Paperdoc

Polypheme
Ambassador
I like DRagor's post above and will add to that.

You have been hit with what I regard as bad use of labels. There are two very different kinds of devices for connecting several fans to one header. Some label them according to their appearance, and that seems to be what you local computer shop did. I label them according to their FUNCTION electrically, as follows.

A SPLITTER is a simple device that connects all its fans in parallel to the signals from the host header. It has one "arm" with a female connector to plug into a mobo fan header, and two or more output "arms" with male connectors where you plug in fans. It has NO other types or "arm". ALL of the power for the fans comes only form the host header, so you are limited to its max current limit for the total draw of all fans connected to that one header. In your case, as you say, OP, that is 2.0 A. max. The fan specs say max 0.39 A per fan for the 140 mm size IF you have the High Speed version, or 0.32 A IF you have the slower "regular" version. For the 120mm size one the max currents are slightly higher. So use of three or four of these fans together on ONE header using a Splitter is OK. A SPLITTER may appear to be just a collection or cable "arms", or a small circuit board with ports around its edge, or a closed box with ports recessed inside holes. A SPLITTER can be used with either 3-pin or 4-pin fans as long as the host header can be configured for that fan type, but it is best to keep all fans on one Splitter / header of the same design.

A HUB is a different device that has those same connections PLUS one extra - an "arm" that must plug into a SATA or 4-pin Molex power output connector from the PSU. It may appear exactly the same as above (three appearances) except for that extra connection cable. So appearance does not ell you - the clue is that connection to the PSU. A HUB draws NO power form the host header so it avoids that limit. It gets power for all its fans directly from the PSU. Power from the PSU (at a fixed 12 VDC) is distributed to all fans, and the PWM control signal from the mobo host header also is distributed. Thus this Hub can control the speeds ONLY of the new 4-pin PWM style of fan; any older 3-pin fan plugged into a Hub will always run full speed. (There are one or two exceptions to this for particular Hubs.)

Based on MY way of labelling, then, BOTH of the devices your supplier showed you were HUBS that get power from the PSU and only work with 4-pin fans. Now, you are only using 4-pin fans so that is not an issue. However, Hubs usually are slightly more expensive that Splitters. And the way you want to use them CAN be done with Splitters according to the amp limits.

A mobo header can deal with the speed signal sent back to it from only ONE fan. So any Splitter or Hub will send back to its host header the speed of only ONE of its fans and ignore the rest. For a "collection of arms" type the common way it to modify the male output connectors so that only one of them has all 4 pins and the rest are missing Pin #3. For circuit board or box styles each will have some label for its only output that DOES send the speed back. A fan header has four functions: provide power, provide control of speed, read the fan speed, and monitor the fan speed signal for fan FAILURE (no speed signal). Using a Splitter or Hub with several fans on one header can do the first two for all fans - they all get power and the same speed control signals. But for the last two those can be done only for one fan - the header cannot read speed signals from the others, nor can it detect failure. So YOU the user need to verify from time to time that all fans still are working.

As DRagor said above the connections for LIGHTS in the fan frames are completely independent of their MOTORS, so I'll address only the motor connections next. You have six case ventilation fans and two (possibly three) mob headers to feed those. Headers first. See your mobo manual p. 19, 21 and 22. The CPU_OPT header at top front may or may not provide speed control - not clear - BUT is guided solely by the temperature measured inside the CPU chip. This is NOT suited for case vent fans. The SYS_FAN1 and 2 headers are guided instead by a different sensor on the mobo and that is right for case fans. HOWEVER, look carefully at those two SYS_FAN2 headers on the front edge. On p. 21 it says they are subtly different. The B one uses only the older Voltage Control Mode which is NOT ideal for feeding newer 4-pin PWM fans, so I advise you NOT use that one. The SYS_FAN3 / PUMP header at the bottom says it CAN do speed control so you CAN use this one if you choose for a fan group. Just look closely at its details when you go into BIOS Setup. SOME such headers have an item to choose for use with a PUMP (then it does NOT allow speed control) or with a FAN that DOES allow speed control. So you should plan to use the SYS_FAN1 and 2A headers, and possibly the SYS_FAN3/PUMP header.

To fit up to three fans on each header get simple Splitters like this

https://www.amazon.ca/Cable-Matters-Pack-Computer-Splitter/dp/B07PXLHNZ6/ref=sr_1_5?crid=3CCZKZ1R4R47C&keywords=fan+splitter&qid=1648221499&sprefix=fan+splitter,aps,104&sr=8-5

That's a 2-pack of 4-pin Splitters with three output arms each, so you could make two groups of three fans each on two headers. IF you choose to use three headers to make other group arrangements, you just need another of those. Remember to ensure in each group that one fan is plugged into the only output with all four pins.

Make sure you get both the mobo basic manual here

https://download.gigabyte.com/FileList/Manual/mb_manual_z690-ud-series_e_1101_n.pdf?v=ec13eff75a8df216a2cff1380bebcebe

and the BIOS Setup manual here

https://download.gigabyte.com/FileList/Manual/mb_manual_600series-bios_e.pdf?v=bfa5eee853800ace94e292edd59e60cf

In that latter manual see p. 6 on how to configure each fan header. Note you select the particular header at upper left. For your CASE FAN headers set them as:
Fan Speed Control to Normal (default settings)
Fan Control Use Temperature Input to Motherboard
Fan / Pump Control MODE to PWM, not Voltage or Auto
Fan / Pump Stop to DISabled
Fan / Pump Fail Warning to ENabled

Set all the case fan headers you are using the same way, then use Esc to back out to Main Menu and F10 to get to Exit Menu (p. 28). There choose Save and Exit Setup to save settings and reboot.

DRagor above noted at the end the possibility of "tweaking" your fan settings for things like air flow balance and internal case pressure. Leave that until you have everything else set up and some experience to guide you. Then if you have your fans in groups such as front three intakes and rear / top exhausts you can adjust at least one of those headers by choosing a different Fan Speed Control strategy. If you choose "Manual" you get to re-define a custom "fan curve" on the graph for this one header only to change the speeds it will run at for the various temperatures.
 
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