Can someone explain 3pin vs 4pin fan and how to use them correctly?

johnstac

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I started looking into these new Noctua Industrial NF-A14 2000 rpm. They offer them in a 4 pin PWM and a 3 pin. I think I have read how PWM has something to do with the ability of the motherboard to control the fans speed but beyond that, I am really lost. I am going to have a combination of radiator fans and case fans. I'm not sure if I should buy all 4 pin or no? For example on a 480mm rad, do I need just 1 PWM and the other 3 are controlled off of the PWM? What about case fans? My motherboard has a limited number of fan ports. How do I control the extra fans?

Lastly, this new Noctua industrial is a 2000 rpm fan but some of the reviews indicate that it is tolerable at the lowest speed. What is that lowest speed? Can the fan be made to spin at less than 2000 rpm? What is the slowest it will spin at?

Thanks for the help.
 

i7Baby

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You use 4pin for cpu coolers. They incorporate a pwm pin (high efficiency speed control).

You use 3 pin fans for case fans. They use variable voltage speed control.

For custom cooling, usually the pump is contrlled by the motherboard cpu fan header (4 pin) and the radiator fans are controlled either by the case fan (3 pin) motherboard headers or by a module eg Corsair h100i.

Fan speed can be altered by the motherboard (UEFI) or a fan controller. If neither and a fan is running straight off 12V it'll run flat out. You can then use a resistor in series bulit into an extension lead to slow the fan down.
 
PWM stands for pulse width modulation.
A motherboard controls speed by intermittingly sending a current pulse to the fan.
With a three pin connection, two are voltage and one is a speed sensor.
Most motherboards have 4 pin for the cpu at least. Normally, if you put a three pin there, it will run at full speeds. Noctua gives you a couple of voltage reducing adapters to reduce that speed.
New motherboards have the ability to control speed not only from the 3 pin pin connectors, but also from the 4 pin cpu connectors with 3 pin headers installed.
 

johnstac

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I will be using a Asus Deluxe Z-97 which supports 4 or 3 pin case fans. Let me ask the question in a different way. I read something awhile back about wiring multiple fans to one fan header. They explained that instead of risking burning out the header by drawing to much voltage (or amperage, IDK), there is a way to route power to the fans using molex/other and then controlling all of those fans with one lead on a 4 pin connector to the fan header. Does this make sense to anyone? I bought a Cooler Master 935 Stacker and will be using two 480 rads. I need a way to run 4 fans from each radiator to one mobo header for each.

I don't have much experience with this and so I just want to know whether to purchase all 4 pins, or in this case just two 4 pin and the other six 3 pins? Clear as mud?
 
If you want to run fans at full speed, you can attach them directly to the power supply.
If you want to adjust those fans as to speed, you can use a fan controller or voltage reducing adapters.

If you want dynamic control of fan speeds based on temperature or such, you need motherboard involvement or perhaps a temperature sensing fan controller.

It is not bad to run fans at a constant speed, the steady drone is probably less annoying than a changing tone.

On the ASUS motherboard, I think it probably has the ability to control 3 and 4 pin fans from the motherboard header. I use a ASUS maximus VII gene and it has that capability.

My suggestion first is to not buy any extra fans until you know that you actually need them.
Most likely, you will be more flexible using 4 pin fans for the cpu cooler and 3 pin fans for case ventilation.

Lastly, water cooling for haswell seems to me to be a ineffective use of your budget.
Haswell will OC modestly. When you get to 1.25v, temperatures rise rapidly. That is probably at 4.4 with a decent chip. How much more do you really need? A top cooler, either air or liquid will not raise that number without a voltage increase past 1.3. As you increase voltage past that, your longevity and stability of the chip will be impacted.
My take is to spend the $100 extra you pay for a top cooler on faster parts in the first place. Use it on a 4690K to 4790K upgrade or on a faster graphics card or on a SSD.
 

madcratebuilder

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You want a fan hub or controller, many variations. This is basic, psu provides power for the fans and cpu header controls speed with PWM. You can get controllers that control 3 pin fans with voltage control. The Noc fans can run under 500rpm at low voltage. The new NF-F12 runs just over 2k rpm and are very nice, 4mm of h2o and quiet. They are identical to the 1400 rpm F12's but have a more powerful motor, 0.1A vs 0.05A.

 

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