Hi folks, I'm having some trouble deciding on the right fans for a Norco-4224 case. Listed are the basics of what I have gathered from various forums, please comment if I'm off-base with anything.

 

Basics

-case fans are either 3-pin or 4-pin

-the 4-pin fans are PWM fans meaning they have variable speeds depending on the temp of the MOBO/CPU

-PWM fans require a MOBO with 4-pin PWM ports

 

The three 120mm fans I'm looking at for the middle fan board of the Norco 4224 are the:

 

Noctua NF-F12 PWM (4-pin PWM, 1500/1200rpm max.)

Noctua NF-P12 PWM (4-pin PWM, 1300/900rpm max.)

Noctua S12A PWM (4-pin PWM, 1200/900rpm max.)

 

Q1) Which one should I get for the middle fan bracket on the Norco 4224? Being positioned in the middle of the case (so not realy an intake or exhaust fan), I'm not sure if I need the higher static fan of the F12, or a higher flow fan.

 

Q2) Why is the Noctua NF-P12 fan listed with 3 different speeds (1300/1100/900rpm) but is only a 3-pin fan? I thought variable speed fans had to be 4-pin PWM. I'm completely confused as to how a non PWM fan can have variable speeds.

Q1) IMHO, if you will use PWM to control the fans, you should take a look into Noctua NF-F12 iPPC 3000 PWM. They are PWM fans and move loads of air if needed;

 

Q2) Because they have an adaptor that have a resistor on it that diminishes the voltage and the RPM;

Q1) IMHO, if you will use PWM to control the fans, you should take a look into Noctua NF-F12 iPPC 3000 PWM. They are PWM fans and move loads of air if needed;

 

Q2) Because they have an adaptor that have a resistor on it that diminishes the voltage and the RPM;

 

Thanks for the info and answering my question about variable speeds.. I'll look into the Noctua NF-F12 iPPC 3000 PWM. The high 3000 rpm fan may be too loud for my applications though.

 

I also found additional information to my own questions through these helpful wikipedia links:

 

https://en.wikipedia.org/wiki/Computer_fan

https://en.wikipedia.org/wiki/Computer_fan_control

 

Basically, a computer fan be variable speed by either linear voltage regulation (e.g., resistors, 3 pin) where the voltage input is proportional to the fan speed or by PWM (pulse-width modulation, 4 pin) where the additional 4th pin is a control signal to determine the fan speed. The advantage of PWM is that the voltage remains constant. The disadvantage to 3 pin methods is that they can add heat to the system.

 

Static pressure as defined by Wikipedia is:

 

A fan with high static pressure is more effective at forcing air through restricted spaces, such as the gaps between a radiator or heatsink; static pressure is more important than airflow in CFM when choosing a fan for use with a heatsink. The relative importance of static pressure depends on the degree to which the airflow is restricted by geometry; static pressure becomes more important as the spacing between heatsink fins decreases. Static pressure is usually stated in either mm Hg or mm H2O.