H100i and powering 4 fans question

[Medwynd]

Parts:
H100i
4 x Cougar Vortex CF-V12HP PWM fans
ASUS Maximus VI Hero motherboard

I am looking to run the H100i in a push/pull configuration. I do not plan on using Corsair Link and do plan on using FanXpert 2 that is part of the AI Suite that comes with the Hero.

The Hero only supports a max of 1A on the CPU_FAN connector.
The Vortex is rated at 0.31A according to the fan sticker.

Originally I had planned on connecting all 4 fans to the y splitters and then connecting them to the block. It looks like the pump has a sata power connector and a 3 pin fan header connector. Does the H100i power the fans from the 3 pin, the sata power connector, or both? Does the 3 pin connector need to be hooked up to control the pump speed?

Could I hook up the sata power and leave the 3 pin connector unhooked. Then plug 2 fans via the splitter into my CPU_FAN header and plug the other splitter into the CPU_OPT header?

 

[lehtv]

I recommend connecting the pump wire onto the main cpu fan header and the fans onto the cpu_opt header. To do that you need an Akasa Flexa FP5 5-way pwm splitter ($10 at frozencpu) it gets power directly from the PSU

 

[Medwynd]

Interesting, thanks for the idea. I wonder how the motherboard would handle controlling the fan speed when they are just connected to the opt header, since it is probably just a mirror of the main cpu header.

It looks like the connector on the h100i only reports back the rpms of the pump.

 

[lehtv]

Yep, the pump's wire is used only for reading its RPM, not to control it. The pump will always run at 100%.

The motherboard will control the fans exactly the same whether you have the pump connected or not

 

[Medwynd]

Yep, the pump's wire is used only for reading its RPM, not to control it. The pump will always run at 100%.

The motherboard will control the fans exactly the same whether you have the pump connected or not

I guess I am curious as to how the motherboard will adjust the fan speeds. If it thinks the thing plugged into CPU_FAN is actually a fan and it is actually reporting say 2000 rpms on the pump will it then try to ramp up the fans connected to CPU_OPT to 200 rpms as well.

 

[lehtv]

I'm not entirely sure but I think the motherboard only cares about the CPU load and temperature. It will supply the fan with a PWM control signal which is just the duty cycle (the percentage of time it should be turned on) divided in equally long pulses. The fan's electronics will translate the PWM signal into RPM even though the fan is constantly receiving full voltage from the power wire. The PWM signal's strength is determined by CPU load and temperature, adjusted by the chosen fan control profile (e.g. silent or turbo). Then the fan just reports back the RPM for monitoring.

 

[Medwynd]

I'm not entirely sure but I think the motherboard only cares about the CPU load and temperature. It will supply the fan with a PWM control signal which is just the duty cycle (the percentage of time it should be turned on) divided in equally long pulses. The fan's electronics will translate the PWM signal into RPM even though the fan is constantly receiving full voltage from the power wire. The PWM signal's strength is determined by CPU load and temperature, adjusted by the chosen fan control profile (e.g. silent or turbo). Then the fan just reports back the RPM for monitoring.

I was thinking that perhaps both headers worked in conjunction so the fans hooked up to both headers would try to run at the same speed to try to avoid any cavitation issues. I threw up a post at the asus boards to possibly try to get an answer from them on the behavior. If I hear anything I'll report back