Question Should I have more intake fans because intake has dust screen?

paqmanbiker

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Couple of cooling questions here, but first off, an intro to this particular build. I'm using this case, with an AsRock B560M PRO4 mobo I think I got my cases mixed up when shopping, and thought this was one that had a lot more drive bays than it does. I'm not super pleased with it, and I don't need the RGB LED's and tempered glass, but I can't really return it without losing a bunch on return shipping and restocking, so I'm living with it lol. It will actually be fine for a couple years till I need more space for hard drives. At which point, I can always do external drives, or just get a new case then. But I do like how easy cable management is in it, which I think helps with cooling. It's mainly a plex server and home file server.

So on to my questions. The front three fans (intake), have a dust cover on them, which I'm assuming restricts air flow a bit. I've removed the dust cover on the top, as those are exhaust fans. So I have two exhaust fans on the top, and one exhaust fan on the back. My question is, since the intake fans are a bit restricted because of the dust cover, I've probably got a negative pressure situation. I'm assuming I want to aim for slightly positive pressure (if not neutral), so I either need to decrease the exhaust, or increase the intake right? There really isn't a spot for another case fan. There is a mounting point for a fan on bottom of the mobo compartment that goes into the PSU compartment, but it really wouldn't be taking in cold air from outside, it would taking warm are from the PSU/HDD area. So Should I just remove one of the exhaust fans, so I have three intake fans (restricted by the dust screen), and two uninhibited exhaust fans?

Also, currently, the three intake fans are plugged into the PSU, and the three exhaust fans are plugged into the mobo. But this machine will be in an A/V closet of sorts and used mostly headless, so noise is not really an issue. Maybe I should just plug all of them into the PSU, so they are always running at MAX speed?

Thanks for your time, any advice would be appreciated!
 
So Should I just remove one of the exhaust fans, so I have three intake fans (restricted by the dust screen), and two uninhibited exhaust fans?
Yes. Remove top fan closest to front.
Or you can remove both top fans. Warm air gets expelled through top anyway.

But this machine will be in an A/V closet of sorts and used mostly headless, so noise is not really an issue.
What kind of A/V closet? It still needs to have openings for air intake and exhaust. You can't have it totally sealed off.
 
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paqmanbiker

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Yes. Remove top fan closest to front.
Or you can remove both top fans. Warm air gets expelled through top anyway.
Ok cool, I can do that, thanks!

What kind of A/V closet? It still needs to have openings for air intake and exhaust. You can't have it totally sealed off.
It's more of a room than a closet. When I finished my basement, I built our screen wall about 3 feet from the foundation so I could inset a media cabinet into the wall, and house all of my networking and A/V equipment back there. So it is about 3' x 20'. Also, the media cabinet/shelving does have some open plates for wiring to go back into that room so it's not fully sealed off anyway. I think it has enough airflow in that room. Although It is not insulated from the outside, so in the summer time it does get kind of warm in there. I don't think it gets over 80-85 F though.

Edit: I made it sound like this PC is in that media cabinet. It's not. It's just on a shelf in this 3x20' room. The media cabinet is open to the home theater room and just goes through the wall into this room. It's where I put our game consoles, Receiver, etc for access to the main room.
 

Paperdoc

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Just to check a detail about your six case vent fans. Today's fans that have LIGHTS in their frames have TWO cables from each fan - one for the motor, and separate one for the lights. An older design, LED Fans, had only ONE cable, and a single colour of lights in the frame for which there was no control over them. These older LED fans use more power from a mobo fan header, so that's a factor to consider in using SPLITTERS. For this purpose, fans with NO lights in them are not a concern. So, I assume you do NOT have the older LED fans - correct?

Next point: IF the three front fans supplied with the case have on their motor cable ends standard fan female connectors (either 3-pin or 4-pin), you do have the option to connect those to a mobo header for automatic control, rather than to the PSU for fixed max speed. So, do they have that type of connector?

I agree with you and prefer that the case have slightly higher air intake rate than exhaust, so that there is a small internal positive pressure to prevent entry of dust at case air leakage cracks. But this is secondary to ensuring adequate air flow for cooling at all workloads. And you are right to conclude that dust filters on the front intakes reduce their air flow capacity slightly.

In your situation, what you have done already is the simplest arrangement. It ensures the max possible air intake rate from the front since those fans always operate full speed. Having the three exhaust fans on automatic speed control by the mobo (based on a temperature sensor on the mobo) means that overall case cooling will be controlled by slowing down the exhaust fans when appropriate while the intakes are running full speed. Net is that, until workload gets very high, there will be a positive pressure inside. At very high workloads that may be reduced to no positive, or to slightly negative. But at that point, your interest is in max cooling, not in less dust. So overall that's a good plan.

Removing one top exhaust will only have the automatic system run the remaining two exhausts a bit faster to achieve the same cooling, EXCEPT when max cooling is required. At that state, you will have LESS cooling than the three exahusts can give, so that is not as good a plan.

There are more complex arrangements that can be done by connecting the front intakes to mobo headers for automatic control of their speeds, but that is not necessary. IF you want details of that, though, post back here.
 
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As long as intake fans are causing the air to rise up, there should not be a problem. Giving your PC more of an outlet more intake can help balance the process given the number of fans you have.
 
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paqmanbiker

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So, I assume you do NOT have the older LED fans - correct?
Correct, in fact the fans I purchased separately are not LED fans at all, no lights. The front three supplied with the case have LED's, and the fan that came with my CPU cooler has LEDs.

Next point: IF the three front fans supplied with the case have on their motor cable ends standard fan female connectors (either 3-pin or 4-pin), you do have the option to connect those to a mobo header for automatic control, rather than to the PSU for fixed max speed. So, do they have that type of connector?
Wow, I'm pretty dumb. So I just realized that all the fans I have, with the exception of the cpu cooler fan, are only 3-pin fans. The ones that came with the case, as well as the ones I purchased, are all 3-pin. So I guess that answers that question doesn't it lol. Means they are going to go max speed whether I plug them into the motherboard or not!

Removing one top exhaust will only have the automatic system run the remaining two exhausts a bit faster to achieve the same cooling, EXCEPT when max cooling is required. At that state, you will have LESS cooling than the three exahusts can give, so that is not as good a plan.
Seeing as my fans cannot control their speed, I suppose having just the two exhaust fans is the best case for me? Otherwise I would be running 3 fans at max speed all the time and would have negative pressure?

Thanks for all the advice.
 
So I just realized that all the fans I have, with the exception of the cpu cooler fan, are only 3-pin fans.
Means they are going to go max speed whether I plug them into the motherboard or not!
Not exactly.
On modern motherboards with 4pin fan headers usually it's possible to choose fan control mode from linear voltage to pwm.
For 3pin fans you have to use linear voltage control mode and they will be controlled just fine.
If you set control mode to pwm, then 3pin fans won't get controlled. Will run either at 50% or 100% all the time.
 

Paperdoc

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Ah! Now we've reached WHY I asked for fan details. A mobo header CAN control the speed of 3-pin fans. Further, several such fans can be connected to one header correctly configured using a simple SPLITTER, but NOT by using a HUB. Those are two different devices. A SPLITTER gets all fan power from the header, so the max current consumption of all the fans connected to ONE header needs to be checked. A header can supply up to 1.0 A max current. Most fan motors use 0.10 to 0.25 A max, so three on one header using a Splitter is OK. HOWEVER, the older LED Fans I mentioned use more power because of their LED's. THAT is why I asked specifically if those fans have TWO cables from them - separate cables for the MOTOR and the LIGHTS. As long as they do have two cables each, then their MOTOR max currents will be OK for grouping on one header with a Splitter.

So you have six fans total for the case. Three in front with lights, ASSUMING they are the 2-cable newer ones, not LED fans, can be connected to one header using a Splitter. Then the three exahust faqns (top and rear) can be connected to another header using a second Splitter. Both headers can be set to use Voltage Control Mode (aka DC Mode), and NOT the new PWM Mode.

If you need help finding Splitters, post back here. BIG hint: a HUB has three types of "arms" to make connections; one arm type must plug into a power output from the PSU for fan power. A SPLITTER has only two types: it has one arm to connect to the mobo, and several output arms for fans.
 

rakibfahadgts

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Aug 4, 2018
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Couple of cooling questions here, but first off, an intro to this particular build. I'm using this case, with an AsRock B560M PRO4 mobo I think I got my cases mixed up when shopping, and thought this was one that had a lot more drive bays than it does. I'm not super pleased with it, and I don't need the RGB LED's and tempered glass, but I can't really return it without losing a bunch on return shipping and restocking, so I'm living with it lol. It will actually be fine for a couple years till I need more space for hard drives. At which point, I can always do external drives, or just get a new case then. But I do like how easy cable management is in it, which I think helps with cooling. It's mainly a plex server and home file server.

So on to my questions. The front three fans (intake), have a dust cover on them, which I'm assuming restricts air flow a bit. I've removed the dust cover on the top, as those are exhaust fans. So I have two exhaust fans on the top, and one exhaust fan on the back. My question is, since the intake fans are a bit restricted because of the dust cover, I've probably got a negative pressure situation. I'm assuming I want to aim for slightly positive pressure (if not neutral), so I either need to decrease the exhaust, or increase the intake right? There really isn't a spot for another case fan. There is a mounting point for a fan on bottom of the mobo compartment that goes into the PSU compartment, but it really wouldn't be taking in cold air from outside, it would taking warm are from the PSU/HDD area. So Should I just remove one of the exhaust fans, so I have three intake fans (restricted by the dust screen), and two uninhibited exhaust fans?

Also, currently, the three intake fans are plugged into the PSU, and the three exhaust fans are plugged into the mobo. But this machine will be in an A/V closet of sorts and used mostly headless, so noise is not really an issue. Maybe I should just plug all of them into the PSU, so they are always running at MAX speed?

Thanks for your time, any advice would be appreciated!
Positive negative pressure depends only on fans if all fans are of identical model, run through same source i.e. motherboard's own pins and have same speed. Otherwise there are a lot of variables such as fan rpm and airflow (CFM). Hypothetically you can have 10 intakes, 5 exhausts and still you'd get negative pressure because exhausts have much higher CFM at a given speed.
 

paqmanbiker

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Ah! Now we've reached WHY I asked for fan details. A mobo header CAN control the speed of 3-pin fans. Further, several such fans can be connected to one header correctly configured using a simple SPLITTER, but NOT by using a HUB. Those are two different devices. A SPLITTER gets all fan power from the header, so the max current consumption of all the fans connected to ONE header needs to be checked. A header can supply up to 1.0 A max current. Most fan motors use 0.10 to 0.25 A max, so three on one header using a Splitter is OK. HOWEVER, the older LED Fans I mentioned use more power because of their LED's. THAT is why I asked specifically if those fans have TWO cables from them - separate cables for the MOTOR and the LIGHTS. As long as they do have two cables each, then their MOTOR max currents will be OK for grouping on one header with a Splitter.

So you have six fans total for the case. Three in front with lights, ASSUMING they are the 2-cable newer ones, not LED fans, can be connected to one header using a Splitter. Then the three exahust faqns (top and rear) can be connected to another header using a second Splitter. Both headers can be set to use Voltage Control Mode (aka DC Mode), and NOT the new PWM Mode.

If you need help finding Splitters, post back here. BIG hint: a HUB has three types of "arms" to make connections; one arm type must plug into a power output from the PSU for fan power. A SPLITTER has only two types: it has one arm to connect to the mobo, and several output arms for fans.
So my intake fans, that came with the case have LED's, but the exhaust fans that I purchased do not. But because this is not out where noise is going to bother us, would it really hurt to just have them all plugged into the PSU going full speed? If I've got the three intake and only 2 exhaust? Not trying to oversimplify, I'm just not super concerned with keeping them quiet, so don't mind them running max all the time.

Positive negative pressure depends only on fans if all fans are of identical model, run through same source i.e. motherboard's own pins and have same speed. Otherwise there are a lot of variables such as fan rpm and airflow (CFM). Hypothetically you can have 10 intakes, 5 exhausts and still you'd get negative pressure because exhausts have much higher CFM at a given speed.
Yeah I hear ya. Honestly just trying to get it "good enough", so that I can keep slightly positive pressure, and keep the thing cool. I'm not worried about noise. I can see there are a lot of variables in play here. But I've noticed that even at full speed, these things are dang quiet. And It's where nobody will hear it anyway. So not sure how to make sure I have the right pressure.
 

Paperdoc

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You are right. The "downsides" of running the front fans full speed always fed from the PSU are three: more noise (OK with you); more power consumption (VERY little more); and shorter fan life - maybe you "lose" ½ to 1 year over several years of possible lifetime, not a big deal for many.
 

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