Question My sffpc has 1 sys_fan header and 1 cpu_opt, which setup for an intake & exhaust fan should I use?

[Coyle]

Should I put them both on the sys-fan header with a splitter or can I attach one of them to the cpu_opt, and if so which would be best to go there, the 200mm intake fan or the 80mm exhaust fan? Thanks!

Edit: I see my motherboard has Smart Fan 6 which allows CPU_OPT header to be switched from the default CPU setting to System 1, which is also the setting of SYS_FAN. Curve profiles can also be adjusted if needed, though has a TUNE ALL feature as well.
So does that mean I'm ok to use CPU_OPT header for one of my fans, and if so does it matter which one? Or, do I still need to put the both on SYS_FAN with a splitter?

This is my first gaming build and don't have any experience with cooling systems.

 

[Brainonska511]

You should be fine using the extra CPU fan header as a system fan header, especially if you can change settings for it in BIOS. It's probably originally there for people using AIOs that need the extra header for the pump.

Nothing wrong with using a splitter either, but if the fans are different sizes or types (eg, 3-pin and 4-pin), you might see some weird things with fan speeds.

 

[mindless1]

Yeah, one fan per header gives the best individual speed control for different types/speed-range/etc fans, except you're stating that if you switch it away from CPU, they both share the same setting? If so, I'd try it and see, but the best match of speeds might be achieved some other way. 200mm front fan doesn't need nearly as much RPM to move air compared to the 80mm, yet is more audible at same RPM (all else equal except it being in the front, potential line of sight path to your ears?). If any are 4 pin, plug into a 4 pin header if available.

 

[Brainonska511]

Considering that case, you might be able to get away without the exhaust fan at all, especially with such a large intake. 80mm fans don't move a lot of air.

 

[Paperdoc]

I advise you keep the small exhaust fan in use. The case does need exhaust.

Do NOT worry about making fan SPEEDS match. Obviously with two fans so different in size, the AIR FLOW each generates will be very different at the same speeds, and it is that FLOW that matters. With such mismatched sizes the air flows will never be equal anyway.

FYI, the signal sent out by any fan header is NOT a speed setting. It really is a "% of full speed" setting, so the actual speed of each fan for the SAME signal is different.

If you are using the two headers, one for each fan, I suggest you set the "fan curve" of both headers the same.

 

[Fallen Kell]

I know this is a couple weeks old, but be sure to check the overall power limits of the fan headers (amperage) to make sure it can handle multiple fans on that header if you plan on attaching a splitter or connecting daisy chained fans that have that capability. It may initially work for a bit if you are around or just exceeding the amperage limit, but it will eventually fail, usually damaging that header on the motherboard (blowing an internal fuse that would need to be replaced using a hot air station) and/or worse case blowing part of that power rail within the motherboard (on a cheap board that didn't protect itself from over-draw to an external connector that will provide power).

 

[Paperdoc]

Notes regarding power limit for a mobo fan header. All computer mobo fans operate on a power supply at 12 VDC and the limit of the header's ability to supply power to fans is the max AMPS current they can draw. (Older design 3-pin fans are supplied with power that VARIES from 12 VDC max down to about 5 VDC min. for slowest speed, but the header limit still is the max amps.) In general, EACH such header can supply up to 1.0 A. SOME can do more IF clearly specified in the mobo manual. When connecting more than one fan to one header by a Splitter or Daisy Chain you must add up the max current amps spec for each fan in the group and ensure this total does not exceed the header limit. Find that spec on each fan's label or in its maker's web page specs.

Splitters and Hubs are two very DIFFERENT types of devices for connecting more than one fan to a header, but sellers OFTEN use the labels as if they mean the same thing. They are NOT the same. Both types of device may appear visually as a collection of cable "arms", or as a small printed circuit board, or as a closed box with connectors recessed inside openings. These days all Splitters and Hubs are designed with 4-pin input and output connectors.

A SPLITTER is a simple device with only two types of connections. It has one "arm" or connection to the mobo fan header to get all power and control signals. It has two or more "arms" or output connectors where you plug in fans. It has NO other type of connection. All of the power for its fans comes solely from the header, so the 1.0 A limit applies. A Splitter MUST be used for 3-pin fans because that type cannot be controlled by a PWM signal from the mobo; it can be used for 4-pin fans also.

A HUB can look very much like a Splitter, but it is different in one particular and easy-to-see item. It has a THIRD type of connection that must go to a 4-pin Molex or a SATA power output from the PSU. This device gets all power for its fans from the PSU directly and does not draw any fan power from the host header. Hence the header's amps limit does NOT apply. The new amps limit is that of the power connection to the PSU: a SATA connection can supply up to 4.5 A max; and a Molex connection can supply 10 A at least, sometimes more. You are UNlikely to exceed either limit by using even a lot of fans. BUT a HUB can control the speed of its fans ONLY by sharing the PWM signal from the host header, so the fans connected to it MUST be the newer 4-pin PWM type. Any 3-pin fan fed PWM Mode signals from a header will always run full speed.

A mobo fan header can deal with the speed signal sent back to it (on Pin #3) of only ONE fan. So all Splitters and Hubs will send back to its host the speed of only ONE of its fans and ignore all the rest. You will never "see" the speeds of "the rest" anywhere. For a unit that looks like a collection of cables, only ONE of the outputs will have all 4 pins in it. All others will be missing Pin #3 so they cannot send their fan speeds anywhere. For a unit like a circuit board or box ONE output will be marked as the only one that sends its speed back to the host. You should ensure that the one header that does send a speed back IS used.