How few fans can I get away with in a pc?

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How few fans can I get away with in a pc?

Postby shild on Sat Oct 28, 2017 8:52 pm

Trying to reduce the noise in a pc as much as possible. This is for a cnc machine so it doesn't have to be too fast. It currently has the fan in the power supply, the one for the processor and a through the case fan. Can I at least get away with removing the through the case fan if the ventilation is good?
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Re: How few fans can I get away with in a pc?

Postby tezza on Sat Oct 28, 2017 9:01 pm

Hmm. The through case fan was probably installed for a good reason but out of the three, this is probably the least critical.
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Re: How few fans can I get away with in a pc?

Postby Gibsaw on Tue Oct 31, 2017 12:49 pm

It really comes down to load. If it's under almost no load then just a PSU and CPU fan.... But bear in mind that you may end up with one of the other fans running harder and being noisier than if you had just left it with two. (Does your video card have a fan? They can be really noisy if they run hard.)

You would get a benefit from installing quieter and more efficient fans like the Noctua ones. Obviously that comes down to budget.
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Re: How few fans can I get away with in a pc?

Postby shild on Tue Oct 31, 2017 1:15 pm

tezza wrote:Hmm. The through case fan was probably installed for a good reason but out of the three, this is probably the least critical.
I thought so. I've got one of those temperature monitors with 2 sensors, so I can check before and after. I'm thinking I should stuff one sensor in the fins of the processor heatsink but where to put the other one?
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Re: How few fans can I get away with in a pc?

Postby shild on Tue Oct 31, 2017 1:24 pm

Gibsaw wrote:It really comes down to load. If it's under almost no load then just a PSU and CPU fan.... But bear in mind that you may end up with one of the other fans running harder and being noisier than if you had just left it with two. (Does your video card have a fan? They can be really noisy if they run hard.)

You would get a benefit from installing quieter and more efficient fans like the Noctua ones. Obviously that comes down to budget.
I only remember all the fans running at one speed regardless of load. This pc has a motherboard of about 2001 vintage. They didn't have fans that increase speed with load at that time yet did they? That being said I've got a more modern power supply that I believe is like that but I'll have to swap out the power dongles for older type. I use a graphics card without a fan.
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Re: How few fans can I get away with in a pc?

Postby shild on Sat Nov 04, 2017 7:38 pm

Got an update. tried with a temperature sensor stuffed in the fins of the processor and one on the bearing of the hard drive. Processor was 88 degrees and hard drive was 81 degrees with the through the case fan. Without that fan, processor 92 and hard drive 86. So about a 4 degree difference. I guess it doesn't hurt to run without that fan in this case does it?
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Re: How few fans can I get away with in a pc?

Postby Gibsaw on Mon Nov 06, 2017 10:48 am

Well, that depends... Hard disks should be more around the mid 30's, and yours is already hot enough to burn you. 4 degrees can be the difference between melting lube or not.

I get that you're probably trying to improve things without unnecessary spending, but I think possibly it would be wise to re-examine your objective. If this machine is near a CNC milling machine, why does it have to be so quiet? If the noise is irritating because the CNC is idle 99% of the time, then shut it down or hibernate it 99% of the time, and extend it's service life.

If that's going to cause more nuisance than the noise, then spend some money. If this machine is running a piece of business critical equipment, what's the cost of failure?

There are all sorts of options from Noctua fans to large passive heatsinks to liquid cooling to SSD's (cooler than a hard disk) to replacing the PC itself with more modern cool-running cpu/gpu combos... If you only want to look at cooling, then target the NOISIEST fan first. Start here...

https://quietpc.co.nz
https://silentpc.com
https://www.quietpc.com/casefans
http://www.silentpcreview.com
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Re: How few fans can I get away with in a pc?

Postby shild on Mon Nov 06, 2017 2:40 pm

Gibsaw wrote:Well, that depends... Hard disks should be more around the mid 30's, and yours is already hot enough to burn you. 4 degrees can be the difference between melting lube or not.

I get that you're probably trying to improve things without unnecessary spending, but I think possibly it would be wise to re-examine your objective. If this machine is near a CNC milling machine, why does it have to be so quiet? If the noise is irritating because the CNC is idle 99% of the time, then shut it down or hibernate it 99% of the time, and extend it's service life.

If that's going to cause more nuisance than the noise, then spend some money. If this machine is running a piece of business critical equipment, what's the cost of failure?

There are all sorts of options from Noctua fans to large passive heatsinks to liquid cooling to SSD's (cooler than a hard disk) to replacing the PC itself with more modern cool-running cpu/gpu combos... If you only want to look at cooling, then target the NOISIEST fan first. Start here...

https://quietpc.co.nz
https://silentpc.com
https://www.quietpc.com/casefans
http://www.silentpcreview.com

Sorry about this but forgot I was writing in New Zealand Vintage Computing when I wrote this. I meant in Fahrenheit. So with through the case fan it's 31 Celsius processor 27 hard drive. Without through the case fan it's 33 Celsius processor and 30 hard drive. This is in a cool basement of about 19 Celsius by the way. That being said I'm wondering if I can replace the cpu fan with a large passive heatsink?
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Re: How few fans can I get away with in a pc?

Postby Gibsaw on Mon Nov 06, 2017 4:17 pm

You most certainly can. There are a number available, but it's going to come down to clearance in the case.
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Re: How few fans can I get away with in a pc?

Postby SpidersWeb on Wed Nov 08, 2017 6:17 am

One thing I wanted to throw in.... you can take an existing fan that's normally connected to +12 and GND, then connect it to +12 and +5 (no ground). This gives a 7V difference which slows the fan down and can reduce noise a lot when used with a motherboard that doesn't have fan control - while not completely stopping air flow.

Just an optional alternative to ripping out fans that I've used before - although usually on older stuff I prefer cool over quiet.
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Re: How few fans can I get away with in a pc?

Postby shild on Sat Nov 11, 2017 10:31 am

Gibsaw wrote:You most certainly can. There are a number available, but it's going to come down to clearance in the case.
Yeah, I'm thinking about this now!
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Re: How few fans can I get away with in a pc?

Postby shild on Sat Nov 11, 2017 10:34 am

SpidersWeb wrote:One thing I wanted to throw in.... you can take an existing fan that's normally connected to +12 and GND, then connect it to +12 and +5 (no ground). This gives a 7V difference which slows the fan down and can reduce noise a lot when used with a motherboard that doesn't have fan control - while not completely stopping air flow.

Just an optional alternative to ripping out fans that I've used before - although usually on older stuff I prefer cool over quiet.


Good idea! Did not know I could do this. If I want 24 volts can I also use the +12 and -12?
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