Help a PC noob with case fans?

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I've been extensively searching for the answer I need and am just as confused as when I started. I recently bought several pre-built PCs and took a dive head-first into cryptomining (I know pre-builts are almost never worth it, but these were). There's just one major annoyance: lack of airflow. It came with a 3-pin 90/92mm fan for exhaust, and that's it. The problem is that it literally never kicks on except for two seconds at startup. The only way to keep these PCs quiet is to take the side panel off (which I'm not thrilled about for dust reasons). So my research has led me to 4-pin PWM fans that I can manually configure to run 24/7 at light/medium duty. There's a few problems though. #1 is that I only have 1 4-pin "CHA_FAN1" header on this motherboard which is where the current 3-pin fan is plugged in. There isn't a second one. #2 is that the exhaust fan spot ONLY accepts a 90/92mm fan, no other holes to use something else. But then #3 is the real issue I can't figure out. I want to install one fan at the bottom front of the PC to send air (front-->back) through the GPU/PSU area to relieve the stress off of those fans. I can either fit a 90/92mm or a 120mm snugly. Ideally I want a 120 for more & quieter airflow. I know Arctic makes built-in (PST) adapter cables on some of their fans, or worst case I can buy standalone PWM splitters from Noctua. Also, this front fan gets basically zero fresh air as the front cover is completely solid. The goal is to merely move some air toward the rear exhaust. There is absolutely no other space anywhere else to install fans.

But after all my research I'm still unsure if it is okay to mix two different fan sizes (and possibly different brands) on the same fan header. Is that okay? I understand the motherboard will only receive input from the 'master' fan, but I'm unsure if they have to be identical or if it's okay to mix two different fans? Ultimately, safety is #1 and cost isn't an issue, so if I have to use two identical 90/92s, then I guess that's what I have to do to keep it safe. I'm just hoping to keep these as cool & quiet as possible and the case they are in doesn't make that easy. Here's what I have:

20211205_222618.jpg


20211205_222733.jpg


20211205_223915.jpg


And this is basically what I have in mind:

20211205_224016.jpg


Also, one additional question. Due to the space between the proposed intake and exhaust fans, will I need an extension of some sort or will the cables be long enough on their own with a PWM splitter? Thanks!
 
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What about SATA or molex to 3/4-pin and run them all the time?

An aftermarket 120mm fan should have plenty long enough lead to reach to your splitter. Splitter will prob be 2-3 inch long.

I wouldn’t worry about mixing sizes on a splitter.
 
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You should read the manual to the motherboard.

More often that not, the BIOS can control the fan speed, with a standard 3-pin connector.

If you can locate the case manual, you can see what's the max size fan you can put at each location. 120mm is the most common, and you can get it for high static pressure (like on the CPU, or radiators), or one made for max CFM.

Going larger, is better, because then, the fan speed won't be a high, this quieter.
 
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I am not familiar with how motherboard control speed using PWM, but if it is like the standard PWM in industrial or power electronics stuff, then if you run 2 fan in parallel to the same motherboard header, it will try to PWM both fans with the same amount of on/off cycle, and they will have the same "percentage" power between 100% (12V) and 0% (0V). The bigger problem is if you use a splitter, which one of the fan will send the rpm signal back to the MB? It will have to be one or the other instead of both.

If you are using it 247 just keep it simple and use a SATA to fan power adapter, it will only use the 12V and GND and ignore the rest. I personally just wire my fan between 12V to 5V constantly and let it run at 7V. It works great with newer single rail power supply (almost anything these days), especially with a pre-build, and even if you have those older power supply with multiple rail that has fixed current output on each voltage, the amount of current draw from the fan is so small that it won't push the 5V out of spec to above 5.1V, something in the system will use the 5V and drag it back down to a reasonable voltage. If this is still too scary to you then you can find a way to go from SATA to molex to 3pin fan adapter, then at the molex use a pen to push the 12V pin out and swap the 5V pin in, and reduce the power to the fan to 5/12 of original.
 
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OilMagnate

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What about SATA or molex to 3/4-pin and run them all the time?
Sorry, newbie. Can you explain what you mean by this? I know what all of those are, but no idea how this would function.
An aftermarket 120mm fan should have plenty long enough lead to reach to your splitter. Splitter will prob be 2-3 inch long.

I wouldn’t worry about mixing sizes on a splitter.
Got it. So one vote for mixing is okay (but I know not to mix PWM and non-PWM). Good to know regarding the cable length. I wasn't sure. Thanks.
 

OilMagnate

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You should read the manual to the motherboard.

More often that not, the BIOS can control the fan speed, with a standard 3-pin connector.

If you can locate the case manual, you can see what's the max size fan you can put at each location. 120mm is the most common, and you can get it for high static pressure (like on the CPU, or radiators), or one made for max CFM.

Going larger, is better, because then, the fan speed won't be a high, this quieter.
Right, but if I have to buy extra fans anyway, I'm going PWM or going home. And if I buy PWM fans, I shouldn't mix them with non-PWM fans if there's only one header. So while I thoroughly appreciate the advice (and may utilize your advice on the lone fan temporarily just to gain some experience/knowledge), I need to go with 4-pin. But sound advice regardless. Thanks!
 

OilMagnate

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I am not familiar with how motherboard control speed using PWM, but if it is like the standard PWM in industrial or power electronics stuff, then if you run 2 fan in parallel to the same motherboard header, it will try to PWM both fans with the same amount of on/off cycle, and they will have the same "percentage" power between 100% (12V) and 0% (0V). The bigger problem is if you use a splitter, which one of the fan will send the rpm signal back to the MB? It will have to be one or the other instead of both.

If you are using it 247 just keep it simple and use a SATA to fan power adapter, it will only use the 12V and GND and ignore the rest. I personally just wire my fan between 12V to 5V constantly and let it run at 7V. It works great with newer single rail power supply (almost anything these days), especially with a pre-build, and even if you have those older power supply with multiple rail that has fixed current output on each voltage, the amount of current draw from the fan is so small that it won't push the 5V out of spec to above 5.1V, something in the system will use the 5V and drag it back down to a reasonable voltage. If this is still too scary to you then you can find a way to go from SATA to molex to 3pin fan adapter, then at the molex use a pen to push the 12V pin out and swap the 5V pin in, and reduce the power to the fan to 5/12 of original.
I just want simple and safe. I'm not too comfortable with the extreme latter part, but I'm intrigued by this "SATA to fan power" adapter. My only hesitation is I'm assuming it will not report back to the MOBO. And assuming that's correct, how will it know to increase the fan speed if something starts cooking? Again, safety is #1 due to my newbie ignorance.
 
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Sorry, newbie. Can you explain what you mean by this? I know what all of those are, but no idea how this would function.
He's saying you can use an adapter like this to power your fans:

 
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I just want simple and safe. I'm not too comfortable with the extreme latter part, but I'm intrigued by this "SATA to fan power" adapter. My only hesitation is I'm assuming it will not report back to the MOBO. And assuming that's correct, how will it know to increase the fan speed if something starts cooking? Again, safety is #1 due to my newbie ignorance.
If you're running 24/7, I'd assume the fans would be running at 100% all the time.
 
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You seem to want cool and quiet. Those two goals are often at opposite ends of the spectrum. I don't know anything about mining computers but I assume they are crunching numbers full time to hope to generate a crypto. I know they use a lot of electricity and don't think you can have both quiet and cool at the same time for this application. My advice would be to buy very high quality fans and run them full blast. Temperature controlled fans are great if you use your PC for routine stuff at home but also game with it or use other high demand programs. This way you get quiet when you're web surfing and it will automatically speed up the fans when you're doing something more demanding. If you're always doing something demanding, there's no benefit of BIOS controlled fan speed.
 

wwillson

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Cool is important, especially when the GPU will be putting out maximum heat. Most of the crypto mining rigs I've seen have no case or the side of the case if left off. Airflow is king and you'll never get enough with just case fans, like I said, leave the side of the case off. Having the case side panel on or off will make zero difference in how much dust the internals collect, as they are dust magnets.
 
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Right, but if I have to buy extra fans anyway, I'm going PWM or going home. And if I buy PWM fans, I shouldn't mix them with non-PWM fans if there's only one header. So while I thoroughly appreciate the advice (and may utilize your advice on the lone fan temporarily just to gain some experience/knowledge), I need to go with 4-pin. But sound advice regardless. Thanks!
If you have an extra 5.25" bay, there are fan controllers you can buy to manually control the fans.
 
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Not sure I understood it all, but

- I'd suggest going 120mm fans if you can. Arctic fans are good value and some come with the PST adapter so you can daisy chain from one PWM connector (historically Artic fans were pretty power hungry so I wouldn't go over 3 fans per plugs, but maybe that's a thing if the past). Same with Noctua adapters, etc (or other brands).

- You can mix match different fans, they will receive the same PWM control signal from the motherboard (probably adjustable in the bios /uefi) and live their life from there (usually basic settings a good balance cooling/noise, and will push the fans to max if temps exceed safe temps)

- can you turn your PSU so it sucks fresh air from under? If yes, I'd consider doing that

- if you have the possibility to add a fan on top (extracting hot air), I'd consider it. Either that or one more "intake" fan...depending on what you prefer, positive or negative pressure inside the case
 
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Why pwm fans they are controlled by bios.. if you are full power all the time just use regular fans at full power.(some fans have switch for low-m-high on them)

Measure and see if 120mm fans fit they are the standard and more options + cheaper + less noise.
 
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I just want simple and safe. I'm not too comfortable with the extreme latter part, but I'm intrigued by this "SATA to fan power" adapter. My only hesitation is I'm assuming it will not report back to the MOBO. And assuming that's correct, how will it know to increase the fan speed if something starts cooking? Again, safety is #1 due to my newbie ignorance.
Correct, any power adapter will not have the rpm reported back to the motherboard. They do not report back something is cooking, and therefore if you are using this approach the fan will be running 100%, instead of PWM control.

The main question is, do you want it to be pwm control and if you do, is it critical and is it loud. I think for a supplemental case fan it is ok, but if you are looking for a CPU fan you got to watch out. Case temp doesn't fluctuate that fast vs chip temp. Picking a big enough for worst-case CFM and dB, then it should be fine with full-on cooling.

p.s. I don't think the rpm signal do much, so if you insist on using a 4 pin to 4 pin splice adapter you probably should just cut off the pin for RPM on one and then let the PWM signal goes to both, and have only 1 RPM to report back, and they all share the 12V and GND. I think most of the aftermarket dual-fan coolers work this way.
 
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Rpm signal doesn't do much except a (usually) configurable error message (On top of the reported value that you can monitor if you want, of course).

I also agree investing in a better cpu cooler could be a good thing, depending of what you're looking for, temps and/or noise, etc.
 
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4 pin has PWM and RPM aware. If both fans are the same the Y adapter only feeds one rpm signal to the board. If your board has fan control capability this would be best. The RPM signal is feedback to the controller so it can adjust speed to match thermal load. You will need to dial this in.

second way... Put the fans on manual controller and adjust the speeds with system under full load until temps are where you want balancing out temp and noise. Fan choice for push pull should be the positive pressure type to move air through the box. Put a cleananable filter outboard of the intake fan.
 

OilMagnate

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If you're running 24/7, I'd assume the fans would be running at 100% all the time.
Since it seems to be a common theme in the replies, I'll clarify the specifics. The one 90/92mm case fan NEVER runs while mining. Ever. With the vented metal side panel on (I also have a glass panel which makes things worse regarding airflow), the GPU temps maintain about 57-59°C. I know this is nice and cool in the mining world which aims for 70°C or below. The tradeoff is that the PSU fan runs very loud while doing this (no idea on how to check percentage or RPM), and the GPU fans run anywhere from 70-100% depending on the individual PC and placement. Four in the same room sounds like a full commercial server room. But when I take the panels off, they all become incredibly quiet. The loudest thing is still the PSU, but it's dramatically quieter, barely a whisper. The GPU temps drop to about 55°C, and the GPU fans run between 30-55% and are almost completely silent. So clearly airflow is my issue, and with a replacement exhaust fan running at a moderate speed and an additional 'intake' fan constantly moving air, I'd assume it will produce a similar result as taking the panel off. The net gain is hopefully less dust, but still less noise.
 

OilMagnate

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You seem to want cool and quiet. Those two goals are often at opposite ends of the spectrum. I don't know anything about mining computers but I assume they are crunching numbers full time to hope to generate a crypto. I know they use a lot of electricity and don't think you can have both quiet and cool at the same time for this application. My advice would be to buy very high quality fans and run them full blast. Temperature controlled fans are great if you use your PC for routine stuff at home but also game with it or use other high demand programs. This way you get quiet when you're web surfing and it will automatically speed up the fans when you're doing something more demanding. If you're always doing something demanding, there's no benefit of BIOS controlled fan speed.
Agreed. And for clarity, my mining computers are just common full size ATX PCs. No ASICs or anything crazy. They really don't use much electricity at all. The 4 I'm currently using consume about $1.05 per day combined <440W @ 10 cents/kWh. I don't necessarily need fans running at full blast. There's just NO existing airflow besides the PSU fan and GPU fan. I'm just wanting to add two PWM fans to move some air. If they run at ~50% they should be fairly quiet, and anything to quiet the PSU fan will make a big difference. My issue isn't temperature, it's noise. So if I've done my homework correctly, then adding a couple of fans (running quietly) should help reduce the noisy PSU fan and relieve some stress off the GPU fan. Hopefully that makes sense.
 
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