120 mm case fans

[rookie1010]

Hello
I got a 120 mm case fan with my antec sonata. it has got a 2 wire leading to a molex connector which i am going to stick into the PSU 2 wire molex connector

the optional 120 mm fan i bought is an antec smart fan, which has got 2 connectors, a 2 wire 4 pin molex which should go into a PSU and a 3 wire connector. should that go into which ever is free between the PWR_FAN and SYS_FAN?

 

[farmercal]

If it were me, I would use the 4-ping molex (whenever possible)

 

[Navid]

Originally posted by: rookie1010
Hello
I got a 120 mm case fan with my antec sonata. it has got a 2 wire leading to a molex connector which i am going to stick into the PSU 2 wire molex connector

the optional 120 mm fan i bought is an antec smart fan, which has got 2 connectors, a 2 wire 4 pin molex which should go into a PSU and a 3 wire connector. should that go into which ever is free between the PWR_FAN and SYS_FAN?

Yes it only has one wire. Then, it is for monitoring the RPM. But, if the 3-pin connector has three wires connected to it, I would double-check. Connect the 3-pin connector alone. Does the fan spin? If not, you are OK; hook it up to any connector on the motherboard if you want to monitor the RPM. If you are not interested in monitoring the RPM, just leave the 3-pin connector disconnected.

 

[ericlala]

OT: does the 3 pin provide the same 12v as the 4 pin from psu? I have a nexus 120mm and it is spinningat a relatively low speed.

 

[FlyingPenguin]

Yes it's 12 volts from the mobo or the 4 pin. However, the reason people tend to recommend the 4 pin is to keep the current draw throug hthe mobo to a minimum.

If your PSU has seperate 4 pin connectors labelled "FAN ONLY" you may want to use those. The PSU will throttle down the fans as needed and they'll be less noisy.

HOWEVER those Nexus fans are ultra-low RPM (they're SWEET fans. I replaced ALL my 120 and 80mm fans in both my rigs with them - they're silent but move a LOT of air) and they may run TOO slow on that connector.

 

[rookie1010]

yes the three pin connector has only one wire plugged in, does it get voltage(wattage) from the mobo through one wire. does not require some sort of ground?

 

[FlyingPenguin]

No. The 3 pin with one wire is ONLY a sensor. Power comes from the 4 pin connector. The 3 pin is ONLY used to provide the mobo with an RPM sensor for the fan, which is optional. If you want to see the fan RPM in Motherboard Monitor for instance, connect the 3 pin to one of the mobo fan headers. Otherwise don't bother.

 

[rookie1010]

you mean SYS_FAN or PWR_FAN?

 

[Navid]

Originally posted by: rookie1010
you mean SYS_FAN or PWR_FAN?

A 3-pin connector with only one wire takes a signal from the fan to the connector to be connected to the motherboard. On the motherboard, you can find connectors for this that are labeled for the case fan (SYS_FAN) or the PSU fan (PWR_FAN).
You can connect that connector to either of those connectors. The only thing this will achieve is that you will be able to monitor the RPM (speed) of the fan using an appropriate utility. It will not do anything else in this case.

 

[rookie1010]

why the 3 pin connector when only one ppin is used in the 3 pin connector?

 

[Raduque]

He keepts explaining it to you. The 3-pin connector is used for ONE THING ONLY: Fan RPM speed measurement. The 4-pin connector is used for power. If still in doubt, plug them both in.

 

[Navid]

Originally posted by: rookie1010
why the 3 pin connector when only one ppin is used in the 3 pin connector?

Can you explain (in detail) what exactly is confusing you instead of a one-liner?

The ground connection is made through the 4-pin connector. So, you have to connect the 4-pin connector. Otherwise, the fan will not work.
If you connect the 3-pin connector, the voltage on the single wire, with respect to ground (carried by the 4-pin connector) will provide some information to the motherboard.
This information is not necessary for the fan to operate. It is only for INFORMATION.

You have 2 choices:

1- Only connect the 4-pin connector. Your fan will work fine. You will not be able to monitor the RPM.
2- Connect both. Your fan will work the same as in option 1. Except, you will also be able to monitor the fan RPM.

So, to answer your question: It is your choice. You use the 3-pin connector for monitoring the RPM; nothing else. You do not have to use it.

 

[rookie1010]

Hello
What i meant was why use a 3 pin connector when we only have a single wire going into the 3 pin connector.
why not a one pin connector with a single wire going into the connector?

 

[airfoil]

Originally posted by: rookie1010
Hello
What i meant was why use a 3 pin connector when we only have a single wire going into the 3 pin connector.
why not a one pin connector with a single wire going into the connector?

So where will the grounding come from? You do need at least 2 connections to complete a circuit. Besides, the 3rd wire provides fan rpm data - it is not necessary but there are folks who would like to monitor rpm as well.

 

[Raduque]

A one-pin connector probably wouldn't fit well on the 3-pin headers on the motherboard.

Airfoil: the grounding would come from the same place it already does: the circuit would be completed by the ground wire on the 4-pin Molex through the PSU and case.

 

[rookie1010]

why does the mobo have a 3 pin connector for sensing i.e. SYS_FAN

 

[Nocturnal]

Originally posted by: farmercal
If it were me, I would use the 4-ping molex (whenever possible)

 

[Navid]

Originally posted by: rookie1010
Hello
What i meant was why use a 3 pin connector when we only have a single wire going into the 3 pin connector.
why not a one pin connector with a single wire going into the connector?

The connectors on the motherboard are 3-pin connectors. That is not up for debate!
Those are used for powering a fan that is powered by a 3-pin connector. The RPM monitor wire is one of the three wires. So, such a fan would be connected to one of those 3-pin connectors and you would be able to monitor its RPM.

Some fans come with a 4-pin connector, as you know so that you can connect them directly to the power supply. But, you will not be able to monitor the RPM since the 4-pin Molex connector does not have a wire for RPM monitoring. The solution is to include another connector to hook up to the motherboard connector to use its RPM monitoring pin.

I hope this helps!

 

[0roo0roo]

do you really need the optional fan? the one in the back does pretty well by itself.

 

[rookie1010]

ah thanks navid
it all makes sense now.

two wires on the molex for power, one on the 3 pin connector for RPM monitoring

am i correct in writing
more power through molex connector sicne it is supplied directly by PSU and less power from 3 wire connector since it is supplied power through mobo.

 

[Navid]

Originally posted by: rookie1010
ah thanks navid
it all makes sense now.

two wires on the molex for power, one on the 3 pin connector for RPM monitoring

am i correct in writing
more power through molex connector sicne it is supplied directly by PSU and less power from 3 wire connector since it is supplied power through mobo.

In case of a fan with a 4-pin Molex connector and a 3-pin connector with only one wire on it, all the power comes from the Molex connector to the fan.

There is no power transferred to the fan through the 3-pin connector. The fan puts a voltage on the RPM monitor pin that the motherboard measures. The information can be in the voltage value or its frequency. The point is that this monitoring of voltage or frequency does not result in any power transfer. If there is any power transferred, it would be very small and negligible.