Building a single-fan MDF case

PeterWelzien · Post by **PeterWelzien** » Fri Feb 15, 2008 1:42 pm

Hi. I've got a server that's running 24/7. It's currently mounted in the cheapest case I could find and using the cheapest PSU. The only modifications I've made is changing the PSU fan to a 800 rpm Noctua (120 mm) and changing the two 80 mm case fans. I don't remember what kind I used, but they were recommended in one of the articles here on SPCR. I've also built a very simple duct between the two CPU heatsinks and the case fans.

The hardware is an old server mainboard with two 1.3 GHz P3:s and two harddrives. The CPU:s carry each a fanless "cubic" heatsink.

This server makes very much noise as it is. I want it as quite as possible since it's running 24/7 and we're living a three room appartment and don't have a basement or attic where I can hide it.

PeterWelzien · Post by **PeterWelzien** » Fri Feb 15, 2008 1:42 pm

I'm planing to build a completely new case out of MDF. Since it's only the CPU:s, harddrives and PSU that produce any heat I'm wondering if it's possible to manage with just one 120 mm fan. I believe that the heat contribution from the rest of the computer is insignificant.

I'm planning to mount the PSU in front of the mainboard and mount the harddrives between the CPU:s and PSU. So the fan draws air through the CPU heatsinks, past the harddrives and then into the PSU and out the top.

I intend to build an airduct between the CPU:s and PSU.

The harddrives will be suspended and the fan will also be somehow decoupled from the case. I might even use some kind of sound dampening material on the inside of the case.

I have two questions:
1) Will it be enough with one fan to cool the system?
2) How thick MDF should I use to get enough stability and dampening of noise and vibrations? I'm thinking 10-15 mm.

This is my first try at building my own case. I've studied some articles here on the site and elsewhere, but I'd appreciate any advice.

tehcrazybob · Post by **tehcrazybob** » Fri Feb 15, 2008 3:14 pm

No, I wouldn't suggest it. The fan in the PSU is not intended to handle the heat of an entire system. It's possible that a good power supply could handle that, but it would require the fan to run at full speed all the time. If instead you used a Nexus or Scythe 120mm fan for the system and allowed the power supply to handle only its own heat, both fans could run at low speed. Even though there would be twice as many fans in the system, it would be far quieter.

For reference, both to you and anyone else who joins the thread, your P3 processors draw ~30 watts each, so the combination is about on par with modern dual-core systems.

Finally, I agree with your estimate for the material thickness - I wouldn't go below 1/2" or 15mm.

Farinorco · Post by **Farinorco** » Sat Feb 16, 2008 3:28 am

As the previous poster has said, if you want to use only one fan to cool everything, it shouldn't be the PSU's one. There are two main reasons, I think:

- The PSU fan normally is regulated depending on the PSU temp, so under low power loads it's gonna be probably too slow to handle the heat load of two CPUs, HDs and the PSU itself.

- The other way around, if such a heat load makes the fan spin faster, it could be actually worse, because the PSU fans at fast speeds are not exactly quiet or silent.

I'd say your best bet would be a similar design but using a quiet 12cm fan as a Nexus or SlipStream (was that the name to the low pressure Scythes?) instead the PSU, and place the PSU in the floor of the case drawing air from the bottom and exhausting to the back ala CM Cosmos, if you can rise the case a little from the floor. Then, the idea of placing the HDs after the CPUs in the airflow path is really good, as they don't have the same cooling needs as CPUs that are critical, so its probably the best idea if you want to use only one fan.

I think that the PSU should be avoided as a case fan in any silent/quiet pc.

Regarding material, I don't know what to say, but I am really interested because I'm just about to start building my own MDF/melamine (not yet decided) case, and I was thinking in 10mm board because of the final size. But now tehcrazybob makes me hesitate... 1/2" are 12,5mm, and I can't get this... I think what I can buy is 10mm, next 16mm. 16mm means 1,2cm height more than 10mm, wooops... it's gonna be really a lot of difference? Will 10mm board do poorly?

(I'm gonna use 20mm Copopren - a noise isolating open cell synthetic agglomerated - in side panels and front panel and door, as depth and width are not a problem, only height)

Sorry if I've some little language mistakes, I do my best with english. And lots of luck with your project

EDIT: Please, do not answer my question here except if you think is going to help the OP too. I don't want to hijack this thread with my own project so I will start my own, I have some other related questions too

PeterWelzien · Post by **PeterWelzien** » Sat Feb 16, 2008 7:00 am

Farinorco wrote:- The PSU fan normally is regulated depending on the PSU temp, so under low power loads it's gonna be probably too slow to handle the heat load of two CPUs, HDs and the PSU itself.

My current PSU fan is a 12 cm 800 rpm Nexus that's running at a constant speed. The PSU was a really cheap one, so it hasn't got a temp regulated fan.

I was thinking maybe to change the fan to a 1200 rpm to be able to handle the heat. But maybe the overall noise level will be lower with two 800 rpm fans. One for the CPU:s and harddrives, and one for the PSU?

Farinorco · Post by **Farinorco** » Sat Feb 16, 2008 7:25 am

I'd separate the heat loads of PSU and components, personally. I believe this would be a better thermal management, because stacking the heat of CPUs, HDs and PSU could result in a excesive heat load for the PSU and cause damage or shorten its life, specially if it's a not so high quality one and you are using a low airflow fan. Probably it would be better cooled in this way with 2 low rpm fans, making the asumption that each one would be enough to cool its assigned heat source, and more quiet than using only a fan to cool everything if you make it spin at the needed speed to cool everything.

On the other hand, I believe that stacking CPU heat on the HDs is not dangerous at all because HDs don't have a high need of cooling, the only concern would be having them completely isolated with more or less stagnant air with constantly increasing temp, or irradiating heat over other components, something that is not going to happen in your design.

But its only a supposition, I'd let more expert SPCR members to give their view on this.

PeterWelzien · Post by **PeterWelzien** » Sat Feb 16, 2008 7:29 am

If I decide to separate the PSU from the rest of the system. I'd probably spend some money on a good PSU with a temp regulated fan. I believe that the PSU won't have to work very hard to supply the system with power.

PeterWelzien · Post by **PeterWelzien** » Mon Feb 18, 2008 6:25 am

I've come up with some new designs. I've no idea how these would work. So I'd like some comments, please.

1)

This is a classic design. The arrows indicate airflow. The dashed lines are airducts. Since the heatsinks for the CPU:s are quite small I use one airduct between them and the fan to ensure that the air is pulled through them. I also use one duct over the harddrives to make sure the air passes over them.

2)

This one would result in a much less restricted air flow and better cooling of the harddrives and CPU:s. Unfourtunatley the rest of the mainboard won't get any cooling. I don't know how much heat it produces so I don't know how bad this would be. The straight airduct design also gives the noise a straight escape path out of the case.

3)

The airduct in this one is really supposed to do a smooth bend and not a right angle turn. Since the computer will be placed on top of a shelf. This design means that booth the air intakes will be as far away from me as possible. And since there are no openings to the front or down, this should result in less noise reaching me. I'm not sure about the fan placement though. My reason behind the placement is that it is as far away from an opening as possible. Resulting in less noise getting out. But maybe it's so quite it doesn't matter?

tehcrazybob · Post by **tehcrazybob** » Mon Feb 18, 2008 6:39 am

Idea #1 will provide the best cooling not only to the drives and processors, but also to the various chips on the motherboard. I'd go for that one.