I currently have two desktops and three servers in my office sitting on the floor (I know this is bad). With that many servers the ambient temperature in the room goes up quickly. I am located in Dallas, TX so during the winter, if the heat is kept low, it is not a problem, but during the summer it easily jumps the room +10 degrees.

I have decided and found a free 42U server cabinet that a hosting company was throwing away to house all of these systems in. One server is in a rack mount case while the other four servers are housed in mid-tower cases. I have purchased shelves for each computer and plan to lay the towers side ways on these shelves (as replacing the cases costs a heck of a lot of money).

I like the idea of housing all of these systems in the cabinet because it will save a lot of room and clean up all of the cabling currently laying all over the office floor. When putting this setup together over the next couple of weeks, I want to address issues with dust and cooling. The server cabinet has a fan on top, front plexiglass door and a rear metal door with vent wholes on the bottom.

First the cooling issues. I know I am going to want to have cool air enter the bottom of the cabinet and exit the top. I do not want the room heating up though as this will make my work area hot and then make the servers warmer as the air eventually reenters the cabinet.

I had an idea to fix this problem, but am unsure if it will work. I was thinking of taking flexible piping and adapting it to the back fans of the computer having the other end of the pipe at the top close to the cabinet's top mounted fan. I was then thinking of creating a duct around the top fan into the attic.

Now I am very concerned that the attic will cause issues with this type of setup because during July/August time frame, the attic is easily 120 degrees F. I could also use the flexible pipe to take it to an attic exhaust vent if it would be better to vent it into the 100 degree air outside (at least there may be wind.

The other option would be to buy a small portable air conditioner. This may be a possibility, but do I want to spend the extra money on power? I bet this increases the noise. Plus they are around $250 on Amazon. What would you all recommend?

Depending on the solution I end up running with above, I would also like to limit the dust that gets into the cabinet. If I were to cut a whole and mount a second cabinet fan on the bottom of the rear door, could I possibly mount a standard home air filter on the other side of that whole?

Thanks in advance for your recommendations. I look forward to reading your interesting ideas.


7 Answers 7


You're on the right track in terms of ventilating the hot air to the outside. You need to cycle fresh cool air in to the room\cabinet and exhaust the hot air out of the room\cabinet. You do not want to recycle the same air around and around. The key is to maintain airflow through the room: bring fresh, cool air in and send hot air out. My opinion would be to use the exhaust duct in the attic to send the hot air to the outside rather then sending it into the attic. If you have adequate airflow you may not need a portable air conditioner. Try it for a few days\weeks with just exhausting the hot air out of the room and see how that works. If it's still too hot for your comfort level (from the server's perspective) then go ahead and invest in a portable air conditioner. Be wary if the air conditioner has a water collection tank that you'll have to manage the emptying of it unless you can hook up a drain hose to it and sent it down the storm drain\sewer.

  • 1
    Congratz on 10k May 14, 2010 at 22:56
  • 2
    Happy 10K! May you be a benevolent ruler. =)
    – Wesley
    May 14, 2010 at 22:58
  • @Holo & Wes: Thanks much. I'm proud to be a part of this esteemed group of professionals.
    – joeqwerty
    May 14, 2010 at 23:11
  • Congrats on the 10K! May 14, 2010 at 23:27
  • W00t! 10K! Rock on Joe! May 15, 2010 at 12:19

I'd agree with joeqwerty. If you invest in a portable A/C, you want one that's self contained (see my comment above). Additionally, the best way to cool it would be to position the A/C in front of the rack, and not try to cool from bottom to top as you suggested in your question. Cool air is denser than hot air, and even with the vent at the top you risk over-heating with your servers that are higher up in the rack. With the A/C in front of the rack blowing into the intakes of the servers will make sure that they stay adequately cool. To your question about ambient noise, if you're running servers in that room anyways, you won't really notice the additional sound output from the A/C.


Exhausting the heat to the attic shouldn't prove a problem, assuming you're going to put a fan in the box to drive the hot air. The heat in the attic won't matter: attics have external vents because of the extra heat, and a little more won't even be noticed. Might even cool it off a bit.

I wouldn't get an interior air conditioner for several reasons:

  • They're loud
  • They're inefficient
  • You'll still have to duct the hot air
  • You'll also have to run pipe for the condensation

Way more trouble than it's worth.

One problem that is worth thinking about is the effect that venting the heat is going to have on your air conditioning. Keeping the cabinet cool will mean running a lot of air into it, most of which is going straight up to the attic. You can lose a lot more cool air that way than would otherwise be warmed up by the servers. You're probably going to want to experiment with heat exchanging until you find something that's good enough for the servers, and still doesn't suck out all your AC.


Edit: Just found AShRAE saying to raise datacenter temperature and intel suggesting outside air for server cooling is fine. Just have a look for the details.

How about another idea: Wolfram alpha states that your local climate is on average max 30 degrees celsius. Sorry I'm a metric guy. This is also the max advisable ambient temp for data centers. So using air up to 30 degrees celsius is no problem.

I would set the whole thing up with a duct to supply cooling air from the outside to the rack and the exhaust to the outside again. That way, most of the time of the year the server cooling would be independant from room heating or cooling. So You don't throw away heat in the winter or cooling in the summer.

I would build in temperature controlled flaps though: If air gets too hot outside during summer, I would rather have a flap opened to take preecooled Air from the inside of the room. Then You have to measure: If exhaust temp > outside temp, You dump the air outside, because if You draw fresh air from the outside it is still cooler than circulating. If exhaust temp < outside temp, you would circulate it in the room, because dumping it outside would draw hotter air to the house from somewhere else.

Lastly if outside temp is > 30 degree celsius you use precooled rom air to stay under 30 degrees entrance temperature.

In the Winter You might want to circulate to use the heat for room heating.

  • Very interesting. I like this idea a lot. I will look into it over the next couple of days. Should be making a decision on everything soon and definitely this info is valuable. Thx May 25, 2010 at 14:44

Thanks so far for the input. I really appreciate it.

Happy 10K joeqwerty.

Satanicpuppy: You bring up a very good point concerning my home A/C or heat which I had not though of. I can't think of anything off the top of my head as a solution at the moment, but technically I need some type of 'valve' that shuts depending on the internal temperature of the cabinet.

I do like the idea of finding some way to cool everything down without the added expensive of a portal A/C unit. Maybe just a fan to blow air to the front of the servers (I knew it was the front but had a brain fart). I can tell you this much, we keep the house around 78 degrees all year around.

Definitely, I will go to Home Depot or something tomorrow and figure out the vent thing. Maybe someone here or there might have a suggestion on controlling inside air loss when its not needed.

Oh one final thing, anyone have any thoughts on a 'filter' to keep the dust out? One thing I thought of was to purchase a fan or something with a air purifier on it. Place something over the air hole and tunnel it into the front of the cabinet with 3 or 4 flexible pipes.


I woke up this morning with a great idea. So far, no research on the AC part, but I am thinking I could use some type of bathroom vent maybe? Not sure if there is any difference between that and a regular fan.

Here is where it gets interesting though. Once a piece of hardware has been established, I setup a circuit with the help of Arduino to control flow based on temperature. Am headed to Home Depot now to do a little research on what is required on venting the heat. I will update soon.


I have made a decision on exhausting the heat from my server cabinet. I went to Home Depot and purchased a 210 CFM bathroom vent fan which has dampers on the top of it to prevent air flow when it is powered off. I will couple that with the cabinet fan and a flexible duct which will connect the top of the cabinet with the intake of the bathroom fan.

To prevent unnecessary leakage of my home A/C, I will use Arduino and build a circuit which will use a Solid State Relay to allow Arduino to switch the electricity on and off for both the cabinet fan and the bathroom vent fan. It will also include two thermistors which will read temperature at the top and bottom of the cabinet. Add some Wiring/C# code to the Arduino; I will be able to set a base temperature and have the Arduino circuit power the fans when it goes a degree or two above what it should be and turn them off when it goes a few degrees below the base.

I should have this project built within the next two weeks and will post a link to it on www.tekcrack.com. I am also considering looking into Proliphix IP Thermostat with remote sensors. This would allow me to control A/C from the web and be able to take readings through out my two bedroom town home. I may possibly even connect the two together along with temperature readings from the server motherboards and use a Windows/Linux program to control the whole thing. We shall see.

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