NZXT Phantom case - Fan question

One is Molex, the other are 3 pin, if I'm not wrong. Can you post a picture of the connectors?

If your case came with fans fitted with 4-pin Molex male connectors you cannot use them with your mobo. The fan systems are different.

Fans with 4-pin Molex male connectors on them have only 2 wires to the connector. They connect to the Ground and +12VDC lines of a Molex power output from the PSU, and they will run only at full speed that way. Several such fans can be connected to one Molex PSU output in a "daisy-chain" or using adapters, because the Molex output can supply a lot of power. Now, there may be some exceptions to the "full speed" thing. Some people buy and install (or some cases come with) third party fan controller modules that power such fans. These controllers allow you to change the voltage to each fan manually. Alternatively, you can buy "low-noise adapters" for such fans that are inserted into the fan connection and simply add a resistor to the wiring so that the fan runs a a fixed speed, but slower than full speed. These fans cannot be plugged into a mobo 3-pin or 4-pin port unless you find an appropriate adapter or do your own re-wiring of connectors. Further, such fans do not have a third (yellow) lead for the speed signal found on other fan designs. Without the ability to connect such a fan to a mobo fan port there is no simple way to control speed of these fans "automatically".

3-pin or 4-pin computer fans are designed to be connected to mobo fan ports and thus may be automatically controlled by the mobo. (In BIOS Setup there usually are other options for each mobo fan port beyond "Automatic", too.) The two designs are different, so your best option is to use only 3-pin fans with 3-pin mobo ports, and 4-pin with 4-pin. In either case, one mobo fan port usually can power up to 2 such fans using a splitter, but no more than 2 per port. Each of these fan types has the Ground and +VDC supply lines plus a third for a speed signal. This signal is generated inside the fan as pulses and sent back to the mobo for counting to display fan speed. It is mainly for information - the mobo does not use the speed signal for fan control - but in some cases the speed signal also is used to check that the fan actually is operating OK. "Automatic" control of fan speeds by the mobo is done to meet a TEMPERATURE target (not a speed target), and there are two such control loops. One is governed by a temp sensor built into the CPU chip and fed out to the mobo on one CPU pin; this loop controls the speed of the CPU_FAN (and, if it exists, the CPU_OPT) ports. The second is based on a temp sensor built into the mobo by its maker and placed where they judge best, and it controls the CHA_FAN or SYS_FAN ports of the mobo.

The 3-pin fan system controls its fan speed by varying the voltage supplied to the fan(s) on Pin #2 of the port connector (red wire of a 3-pin fan). These ports are said to operate in "Voltage Control Mode".

A 4-pin fan port works differently. Its Pin #2 always has +12 VDC on it. This system supplies to the fan a new PWM signal on Pin #4 which is used by a chip inside the fan case to control how much of the time that 12VDC supply is actually passed on through the motor, thus controlling its speed. This is called "PWM Mode" control. If you plug a 3-pin fan into a 4-pin port, the fan cannot use the PWM signal to modify the power flow, so that fan always runs at full speed from the fixed +12 VDC supply on Pin #2.

Many mobos now use 4-pin mobo ports for some or all of their ports. Almost all use a 4-pin port for the CPU_FAN. However, since makers are aware that two fan styles are common, for this CPU_FAN port they usually offer in BIOS Setup an option to set the port to operate in true PWM Mode OR in true Voltage Control Mode. Thus you can adjust for the fan type you have purchased for this job. On CHA_FAN ports, this option often does not exist, so you really need to buy case ventilation fans to match the mobo fan port type you will plug into.

For people planning to use many case ventilation fans and wishing to use them all under mobo automatic control, the limit of max 2 fans per port can be avoided IF you are using the 4-pin fan system. You can buy and install 4-pin fan Hubs. Such devices pick up the PWM signal from one mobo fan port and share it around to all of the fans connected to the port, but all of these MUST be of the 4-pin design. The actual power to these fans is not drawn from the limited mobo fan port; it is drawn from a separate connection directly to a PSU output (either a 4-pin Molex or a SATA device power connector) capable of more power than a mobo port.

So, OP, if you want to use automatic control by the mobo of case ventilation fans in your new system, your best option is to by new fans of the 3-pin or 4-pin type (match to the mobo ports you will connect to) and use those. If you opt to use the fans that came with your case and with 4-pin Molex male connectors on them, they will certainly cool your case, but you won't have automatic control of their speed, nor will you be able to "see" their speeds (which you cannot change, anyway). If you use these fans and want to change their speeds, you will need either to buy and install a third-party fan controller (unless one came with your case) or use "low-noise adapters" to fix them at less-than-max speeds.