Question regarding fan power cable for x61 Kraken.

[AhabTheBad]

Hello all,

This is going to be a bit wordy so please bear with me.

I have ordered a NZXT S340 case with a x61 Kraken cooling unit.

The cooling radiator unit comes with two fans but the fan power cable coming out of the pump unit (where the radiator fans connect to) has 4 fan power connectors. I imagined these would all be PWM capable (4 pin) but when checking the installation guide found that three out of the four connectors had only 3 pins.

I checked NZXT support site and found an article about troubleshooting problems with the CAM software detecting fan RPM with this statement:

"The X61/60 have four PWM fan headers that connect to the pump, but only one of these fan headers has the fan tachometer cable(all 4 pins), but all are controlled via PWM based on the one fan's speed.
The reason Asetek did this is because if you threw 4 different fan speeds at the software it would cause problems with reporting.
If you have the two fans connected to two of the 3-pin slave PWM connectors, this could cause issues with CAM software detecting RPM. Check and move one of the PWM fans to the 4-pin PWM connector that has all 4 pins."

I checked the install guide and found that pin 3 (the tach connector) was indeed not present on three of the connectors so this raises an interesting point:

As pin 3 of the connector feeds information back to the computer on RPM and fan speed is determined by the signal fed to it with pin 4 and all fans, both PWM and standard have this pin (pin1 for ground, pin 2 for voltage and pin 4 for PWM), would it be possible for me to plug not only the two coolant radiator fans into the pump (making sure one was in the PWM connector) but also the two rear case fans into the slave connectors? It would be cool (pun intended) to have all my fans controlled by the CAM software to make the airflow as efficient as possible.

I appreciate it is unlikely that the case fans will be PWM by design but from what I have said above I don't think this matters (after all some cases have variable fan controls with a switch that alters the speed of the case fans and I don't think they are PWM either) and I may be mistaken about the pins on the fan connectors and how they effect the fan speed but wanted to check with the community to see if what I have said above makes sense and could be done.

Any comments or advice would be appreciated.

 

[Paperdoc]

What you propose can work ONLY if the case fans are 4-pin (PWM type). The older type with only 3 pins (and three wires from the fan) cannot be controlled by a PWM fan port. 3-pin fans require control by a different mechanism called Voltage Control Mode, in which the voltage supplied to the fan on Pin #2 is varied. A PWM port does not do this, so a 3-pin fan on a 4-pin PWM port always runs at full speed.

Now, even if you arranged to have 4-pin PWM fans for case ventilation, I do not recommend what you propose. CPU cooling is guided by an actual temperature inside the CPU chip measured by a sensor included in the chip construction, and fed out to the mobo on one CPU pin. But ventilation of the case is guided better by a different temperature sensor, one built into the mobo by its maker. That way the general cooling of the interior is based on the temperature the mobo maker has judged to be most important, and not on the temperature inside the CPU chip. For this purpose you should connect case cooling fans to mobo SYS_FAN or CHA_FAN ports. In doing this, remember what I said above: a 4-pin fan port operating in PWM Mode cannot control the speed of a 3-pin fan.

Your case comes with a pair of 3-pin fans so you have three options:
(a) ignore case fan speed control, and let them run full speed; don't bother connecting them to the Kraken unit's PWM connectors because that still won't control those fans;
(b) check the capabilities of the mobo CHA_FAN ports because SOME allow you to set whether they operate in PWM Mode or Voltage Control Mode, and IF you have this feature you can use Voltage mode to control your 3-pin fans; or
(c) Buy two 4-pin (PWM) fans and replace the two fans included with your case.

 

[AhabTheBad]

Thanks Paperdoc.

I have spoken with NZXT and they have echoed your advice so I will plug the case fans into the PSU as normal.

I may buy some replacement PWM fans at a later date but I'll see how the heat is when I put the rig together.