Adding 120mm case fan to OMEN by HP Obelisk Desktop PC - 875-0014

[nicol3]

Hello,

I have an OMEN by HP Obelisk Desktop PC - 875-0014. I want to add a case fan to the top and have some questions. I have not found a clear answer on the community page or other website.

I know that a 120mm fan will fit on the included bracket, and that it would be best to be an exhaust type. The motherboard is an Edoras (SSID: 84FD). There is a SYS_FAN 4 pin header with the rear 80mm case fan connected. There is also a CPU_LC_FAN 4 pin header with the CPU fan/heatsink combo connected. There is one available 4 pin header labeled LC_PUMP. From my understanding, this header should be used for a liquid cooling pump.

Questions:

1. Do I connect the 120mm fan to the open LC_PUMP header or use a Y-splitter to connect it to either the SYS_FAN or CPU_LC_FAN header?
   • I think the LC_PUMP will force the fan to run full 100% of the time. Is there any disadvantage to using this connection for a case fan?
2. Do I need to use a 4 pin connection for the 120mm fan or is a 3 pin connector acceptable?
   • I think the 4th pin is for PWM control. For the fan to not run at 100% all the time, this pin may be necessary.

Any other considerations or information would be helpful.

Thank you!

[old_geekster]

@nicol3 , welcome to the forum.

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@nicol3 wrote:

Hello,

I have an OMEN by HP Obelisk Desktop PC - 875-0014. I want to add a case fan to the top and have some questions. I have not found a clear answer on the community page or other website.

I know that a 120mm fan will fit on the included bracket, and that it would be best to be an exhaust type. The motherboard is an Edoras (SSID: 84FD). There is a SYS_FAN 4 pin header with the rear 80mm case fan connected. There is also a CPU_LC_FAN 4 pin header with the CPU fan/heatsink combo connected. There is one available 4 pin header labeled LC_PUMP. From my understanding, this header should be used for a liquid cooling pump.

Questions:

1. Do I connect the 120mm fan to the open LC_PUMP header or use a Y-splitter to connect it to either the SYS_FAN or CPU_LC_FAN header?
   • I think the LC_PUMP will force the fan to run full 100% of the time. Is there any disadvantage to using this connection for a case fan?  This is correct.  I don't believe that it would cause a problem, but you will have constant fan noise when it is not necessary.  I believe you should use a splitter to run the fan.
2. Do I need to use a 4 pin connection for the 120mm fan or is a 3 pin connector acceptable?
   • I think the 4th pin is for PWM control. For the fan to not run at 100% all the time, this pin may be necessary.  This is also correct.  You will pay more for a PWM fan.  So, if you don't use the feature it is not money well-spent.

Any other considerations or information would be helpful.  You will either use the fan in a Pull configuration (air in) or Push configuration (air out).  You can go to Jayz2cents.com to see what he has to say about airflow in a case.  He explains the difference in positive, negative and nuetral air pressure and what it causes inside of the case.

Thank you!

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[Grzwacz]

Hi,

You are on the right track. You must be having thermal problems with your system.

You want PWM four pin motherboard fan header connections to get the best control on fan speeds.

Connecting a new chassis fan to the liquid pump header is probably not a good idea.

Fan splitters are generally not a good idea.

You could look into getting a modular fan/LED device for connecting additional fans or RGB components.These components need to be powered by a SATA connection and controlled by an open USB 2.0 header on the motherboard. You would need both conditions to use this device.

I have used NZXT components with good results. I am sure Corsair or CoolerMaster also make these components.

Best wishes.

Regards