[SOLVED] Best way to set up case fans without fan headers

[h3r3t1k]

So I'm getting a BQ Pure Base 500DX which has 3 14cm fans. One intake, one back exhaust and one top exhaust. I wanna put the front one in the top and add 3 12cm fans to the front. Now my mobo ASRock B450M Pro 4 has 3 case fan headers where the stock fans will go. I bought an adapter 3pin to 3*3pin which I plan to plug into the CPU water pump fan header. My question is regarding voltage and quiet operation: If I run the header at fixed voltage, will the 12v (that's what I'm assuming I'll get maximum) get divided by 3 providing only 4v? That would not be enough as the 12cm fans require 5v minimum...

What I could also do is use an adapter from SATA to 4pin Molex and from 4pin Molex to 3*3pin with 5v for each 3pin header. That's also an adapter that's available.

Which method would be recommended? I'm inclined to go with the former as it's just one adapter and its quality is superior.

Elaborating: one of the 3 headers allows to read out the fan speed. So first check if all 3 fans are actually running and then check the speed to guess at how much voltage they are getting?

 

[Eximo]

All fans will receive 12V. However, you are tripling the load, the pump header is a good idea, they tend to have a higher output.

4-pin molex will deliver again, 5V or 12V, no reduction of the voltage will happen.

For many fans, a fan controller or hub is ideal. They are typically powered via the power supply, usually SATA these days, but still use the control signal from the motherboard to regulate speed.

 

[h3r3t1k]

But if they all get the same voltage that means that I CAN use the motherboard to regulate voltage for all 3 using the 3pin to 3*3pin adapter? So I just select "DC control mode" and "silent mode" for the water pump fan header and that's it? If 5v is called for that's what all 3 fans will get and all fans will spin equally fast within their tolerance?

 

[Eximo]

Correct.

Not typically recommended to go with more than two fans per header, but it should be relatively okay in this case.

****The CPU Fan Connector supports the CPU fan of maximum 1A (12W) fan power.

*The CPU/Water Pump Fan supports the water cooler fan of maximum 2A (24W) fan power.

Most fans fall in the .08-.20 range.

 

[h3r3t1k]

The fans in question are 5-12v and 3.6w so power requirements would be 900mA at 12v. Easy peasy.

EDIT: They are the "high-rpm" variety that's why the 0.3A.

 

[Paperdoc]

I presume the "3*3pin adapter" you speak of is what we call a SPLITTER that simply converts a single 3-pin mobo header into three 3-pin outputs. It has one arm to plug into the header, and three output arms with pins, and NO other connections. Is that right?

A Splitter simply connects all of its fans in parallel to the power supplied by the mobo header, so all fans get exactly the SAME feed. And all of that power can come only from the header. which has a limit on the max CURRENT it can supply, usually 1.0 A. Now it happens that most of the headers you are planning to use are designed for possible use for a pump, and hence with a higher max current output of 2.0 A per header. The 3-pin fans you have that came with the case all have a max current use of 0.30A, so three of those on one header comes to 0.9 A max, easily supplied from one header. For six fans total, one of the easiest arrangements is two Splitters to connect two groups of three fans each to two headers. For example, your existing three 14 cm 3-pin fans in one group, and the new three for the front in another group.

With 3-pin fans, the header alters the VOLTAGE sent out to change fan speeds. With a Splitter, all fans on that header get that same controlled voltage. If the fans are identical, all will run the same speed, from max down to the minimum they can run without stalling.

Four-pin fans (you don't have any) are controlled differently. They get a constant 12 VDC power supply, but they also receive the new PWM control signal from Pin #4. Inside the motor case there's a chip that uses that signal to control the fan sped. Because this method is different from how 3-pin fans are controlled, it is best not to mix the two fan designs on one header. In your case, though, it would be simple to place your three 3-pin fans on one header with a Splitter, and group the new three (of whichever design, 3-pin or 4-pin) on a second header using another Splitter.

For case ventilation fans, I suggest using the CHA_FAN/PUMP headers - you have three of those. Each of them can be configured in BIOS Setup to use the correct speed control method for the fans attached to it. This is the selection of MODE of the header - either DC Mode for 3-pin fans, or PWM Mode for 4-pin fans.

IF you decide to buy more 3-pin fans for the front, then the 3-pin Splitter type you have will be suitable. IF you decide to buy 4-pin fans for the front, then be sure to get a 4-pinSplitter. (In fact, a 4-pin Splitter can be used with 3-pin fans.) If you set up the fans in two groups on two headers as I suggest, then I recommend this set of configuration options in BIOS Setup. (You must configure each header separately.) See your manual, p. 79.

CHA_FAN/WP Switch to Fan

Control Mode to DC for 3-pin fans, PWM for 4-pin fans

Setting to Standard or Normal to have the pre-set automatic fan speed control system manage all these fan speeds according to temperatures measured on your mobo. The fans will run slow and quiet until your system heats up enough to need more cooling.

Temp Source to Motherboard, not the sensor inside the CPU chip

Doing this will give you automatic control of all the case fan speeds - quiet at low workloads, and increasing fan speeds only when the system actually needs that added cooling - and all done without your having to watch and manage them.

Just a note on a detail. Any fan header can work with the speed signal sent back to it from ONE fan only. So any Splitter will send back to its host header the speed of only ONE of its fans and ignore all its others. Youi will never "see" those "othrers". The most common way to do this is simply to include Pin #3 in ONE of the output arms, and omit that pin on all the other outputs.