[SOLVED] Using CPU OPT fan header to power case fan?

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Hello. Building my first computer, midway through buying parts switched from motherboard with 5 han headers to one with 3 official fan headers for case fans. Right now my case has 5 fans but I dont want to wait for a controller given all the covid shipping headaches. My question:

1. Can I use the CPU opt header? The manual specs say that it is 12W 1A and speed controlled just like the other fan headers
2. Can I use the AIO header if I dont care whether that fan runs at 100% all the time? Can that damage my system?

Thanks!

 

[Paperdoc]

You can do that, and it will not harm anything. It is not ideal and you should change it, but as a quick thing to get going NOW go ahead.

Why not ideal? Your mobo basically has two groups of fan control systems, and each is based on a temperature sensor to decide what fan speed to run. The CPU_FAN and CPU_OPT headers use only the temp sensor built into the CPU chip. The three mobo case fan headers you have use a different temp sensor on the mobo for their guidance. So, using the CPU_OPT for a case vent fan is not ideal because it is guided by the wrong temperature.

As you have realized, a PUMP header normally does no speed control. HOWEVER, check your mobo manual about that header. SOME (not all) mobos make the PUMP header a dual-option one. They allow you in BIOS Setup to choose whether it really is running a pump, or is re-purposed to run a normal case vent fan using the mobo temperature sensor and actually doing fan speed control. Still, that only MIGHT get you one more header to use.

Your simple solution is a pair of 2-output SPLITTERS, like this

https://www.newegg.com/p/1W7-0022-0...cm_re=fan_splitter-_-9SIA9F93GG4938-_-Product

NOTE that this item has only one input (female) connector to a mobo fan header, and two output (male) "arms" for the fans; it has NO third type of "arm" that goes to a PSU power output. Each of these can let you connect two of your normal fans to a single mobo header, which all headers can do. Another alternative is to get the same type of device, but with three output arms. However, that type should not be used with certain older LED Fans that have lights in their frames, but no second cable to power those lights.

When you use a Splitter both fans on it will do the same thing, but only one of them will report its speed to the mobo header and you will never "see" the speed of the other fan on that Splitter. This has NO impact on ability to control speed.

 

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EDIT: I figured out this was a molex connector so that's how I'll be powering my fans for now. Thanks for your help.

Original answer: Thank you very much for your detailed answer. I was just looking through my Antec fan box (how are Antec fans , anyway?) And I noticed these splitters (image hopefully attached)

I don't have my mother board yet so I've been doing all my planning from manuals. Does that connector on the splitter go to anything on a motherboard or is it for a fan controller? Thank you!

https://imgur.com/a/hQuKQaG

View: http://imgur.com/gallery/hQuKQaG

 

[Paperdoc]

You may NOT want to use those to connect all your fans to a Molex output from the PSU.

When you connect a fan directly to a PSU output, it receives 12 VDC power ALL the time, so it can only run full speed. Further, since it has no connection at all to the mobo, the mobo cannot tell you the fan speed, nor can it warn you if the fan fails.

Speed control of the fan is one of the features available from a mobo fan header. Normally for each header the options available are:
(a) Automatic speed control - the mobo constantly adjusts trhe fan speed according to heat generated by your changing workload, and it does that by measuring actual TEMPERATURE, either inside the CPU chip for the CPU cooling fans, or on the mobo for the case cooling fans. This is usually the default setting.
(b) Always full speed for max cooling no matter what you are doing (same as if you connect directly to PSU)
(c) Always fixed reduced cooling no matter what you are doing, gives quieter operation at a sacrifice of reduced heat removal.
(d) Custom - similar to Automatic, except you get to specify the fan speed to be used for several temperatures along a "curve".

In addition, a mobo header will display the fan speed in BIOS Setup and through certain software utilities that can run as Windows apps to display while you are working normally. One such utility usually is included on the CD of software and drivers with the mobo. Further, the mobo normally monitors the fan speed signal for FAILURE and can send you a warning of that so you know to fix it. "Failure" may be no fan speed, or may be speed less than some threshold you may be able to specify, dependent on your fan's specs. In this regard, the limitation I referred to above on the use of Splitters is this. The mobo header can only deal with the sopeed signal sent back to it from ONE fan. So when you use a Splitter, only one fan's speed from that Splitter is sent back to the mobo, and you will never "see" the speed of the other, nor have automatic failure detection on that second fan.

 

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Paperdoc, thank you for responding to all of my questions. I installed my noctua 15 but it was a nightmare and my computer didnt post and there's just absolutely no way to trouble shoot with that monstrosity attached so I'm switching to an AIO. As good the noctua cooler is I would not wish its installation on anyone.

 

[Paperdoc]

You're welcome, and I've replied in your related thread on this topic.