[SOLVED] Only 1 fan header on motherboard.

[R3DJ1V3]

First build: So I got the Gigabyte B450M DS3H motherboard with the cooler master q300l and just read that the Mobo only has one fan connector (and CPU cooler). I wanted to connect another fan (Noctua 1700rpm) as an intake. Should I buy a splitter? Will the connector handle a splitter? And if so, I read that a splitter still only has 1 4pin connector, so only 1 fan has the control of the speed, I have two different fans (case and Noctua) at different speeds, what happens then? At this time, I'm planning to just not use the case fan, and only use the Noctua one, a friend gave it to me and it seems to be better than the case fan. BTW here is my list: https://pcpartpicker.com/list/FL3p4n ||

 

[tennis2]

fan headers can supply 1A typically, which is always enough for 2 fans (sometimes 3) on just a simple non-powered splitter/hub.

Only the speed of the "primary" fan will be reported back to the mobo. Both fans will receive the same PWM/voltage signal though. So no worries really.

 

[R3DJ1V3]

fan headers can supply 1A typically, which is always enough for 2 fans (sometimes 3) on just a simple non-powered splitter/hub.

Only the speed of the "primary" fan will be reported back to the mobo. Both fans will receive the same PWM/voltage signal though. So no worries really.

Thanks for the quick reply, you're awesome! My only worry now though is which one to use as "primary." The Noctua has higher RPMs so will it destroy the other one. I don't really know how PWM works, is it just low med high signal or specific speeds in which case what would happen then? Sorry for the questions, but waiting for the PC parts can really drive people insane. Every time I'm off work, I just keep thinking something will go wrong in the build and destroy everything. With the lockdown, I can't really go out and my friends aren't better at it.

 

[tennis2]

Your CPU heatsink fan is going to be plugged into the CPU fan header. That's the main (most important) fan to adjust speed based on CPU temp. Case fans are quite a bit more forgiving. All my case fans (2 intake, 1 exhaust) run at fixed rpm (1200 - 1400rpm depending on the fan).

 

[Deleted member 2720853]

Sorry for the questions, but waiting for the PC parts can really drive people insane. Every time I'm off work, I just keep thinking something will go wrong in the build and destroy everything.

That's my entire past 2 week experience on this site...

Anyway, you will be alright with a splitter on one fan header. Both fans will run just fine.

 

[Paperdoc]

You won't have any problem connecting those two fans together to the one SYS_FAN header on your mobo - the current use is quite OK. Use a simple 2-output Splitter as you plan, but be careful in reading the listings for those items. I find many suppliers mix the use of Splitter and Hub when they should not. A SPLITTER has "arms" of only two types: one arm ends in a female (with holes) connector to plug into a mobo header; the other "arms" (2 in your case) will have pins in a shroud, with only ONE of then having all 4 of its pins. The Splitter has NO other "arm" that must plug into a PSU output, as a HUB does.

To help a bit understanding these, a fan header has four functions;

1. Provide power to the fan motor;
2. Control the fan speed by sending it the correct signals;
3. Read and display the fan speed;
4. Monitor the fan speed signal for FAILURE, and send out an alarm if that happens.

Your case fan and the new Noctua are 4-pin PWM fan types, so ensure your Splitter is the 4-pin type. See p. 24 of your mobo manual where it describes configuration of your fans. First, select the SYS_FAN header. Ensure settings are
Fan Speed Control Normal (automatic, based on temp at a sensor)
Fan Control Use Temperature Input to Motherboard, not CPU
Fan Control Mode to PWM
Fan Stop Disabled (so it never stops)
Fan Fail Warning Enabled
After making any changes there, be sure to SAVE and EXIT,

The speed of your case fans will be adjusted automatically for you according to the temperature measured by a sensor on the mobo. The signals sent to the fans are NOT specific speed values, and the mobo does NOT need to know what speed the fan actually is at. All it really knows is whether the fan speed currently is adequate to keep cooling working, or whether it should speed up or slow down. And all of that depends only on the TEMPERATURE reading. The PWM signal it sends out will reach BOTH your fans via the Splitter and they both will be controlled. Roughly, the PWM signal commands each fan to run at a % of its full speed, and with two different fans, that means although the % is the same, the actual speed of each fan will be a bit different. Does not matter. NEITHER fan is the "boss" - all control signals are determined by the mobo header based on that temperature sensor reading, and both fans merely do what they are told.

Any fan header can deal with a speed signal coming back to it from ONE fan only, so the Splitter will only send back one fan's speed - from the output arm with ALL 4 pins - and the other's speed is ignored. This has no impact on speed control. It only means that the second fan cannot be monitored for FAILURE from a signal that is not checked, so YOU should verify from time to time that both fans still work.