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Hardware Hacking

A Micro-A/C for a Server Closet? 76

Posted by Cliff from the really!-it's-a-closet! dept.
DiZNoG asks: "I work from home and run two businesses from there. Sick of server and switch noise in my home office, I've been thinking of taking an old hallway closet that used to house the furnace (since moved) and turning it into a literal server closet for my various servers and networking gear. I have 4 servers and various networking gear and even a system for getting everything in and accessible worked out. Bonus, the room already has power and is perfect placement for my access point (already secured, thank you!) However, I am running into problems finding a small air conditioner for the size of room. It's literally 15 sq. ft. and maybe 100-125 cubic feet total. By my estimates that's something on the order of 150-250 BTUs (or less) with the hardware. Does anyone on Slashdot know of micro A/C units to keep such a small area in server friendly temperature efficiently? I did see this homebrew action, but I'm looking for much less maintenance."
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A Micro-A/C for a Server Closet? More

A Micro-A/C for a Server Closet?

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  • Your estimation is probably wrong... (Score:5, Informative)

    by ivan256 ( 17499 ) * on Wednesday October 19, 2005 @05:46PM (#13830835)
    The square footage of the space has almost nothing to do with the size of the cooling unit you need. You need to base it on the wattage of the equipment you're going to put in there instead. Divide the wattage of your equipment by three to get an approximation of the BTUs per hour rating you'll need on your AC unit. Regardless, the laws of thermodynamics require that you will have to cut a vent hole for the heat to exit through even if you're using an air conditioner. As long as you're going to have a vent hole anyway, why not cut two? Put a big slow quiet fan in the top one blowing in, and an air filter in the bottom (or the other way around)?

    If you insist on AC, you probably want something like this: APC NetworkAIR AP7003 [apc.com] or more likely, some other (cheaper, but similar) portable AC unit with an exhaust hose from your local Wal-Mart.

    • Erm - multiply by three, not divide (Score:5, Informative)

      by IvyKing ( 732111 ) on Wednesday October 19, 2005 @07:07PM (#13831307)
      Divide the wattage of your equipment by three to get an approximation of the BTUs per hour rating you'll need on your AC unit.

      Conversion factor: 1 KWH = 3412 BTU
      Multiplying the average (not peak) wattage by 3.4 will get the BTU's per hour of cooling capacity.

      • And maybe a remote. OK, cheapest known brand. My eighty dollar 10,000 BTU Panasonic AC would probably work well. The fact that it's overspecified should translate into reliability, and the thermostat means that you won't be running it all the time. Generally, larger units tend to be more efficient, so you should be saving money everywhere. If the noise troubles you, you might locate it remotely with ducting, which you'll need anyway (although since there was a furnace in there, you should have some ducting
        • > had to be turned off for awhile to defrost

          I have an AC like this in the office where I work. We're the desktop support group, so naturally we keep our door open so people will walk in and ask for help. This means we also air condition the hallway. For some reason, when run like this, the AC unit eventually fills up with water and starts spraying it all over our precious computers. Instead of choosing between water-free computers and a cool room, we got a fish tank pump, duct-taped some tubing on to
        • Generally, larger units tend to be more efficient, so you should be saving money everywhere

          not true. you are confusing size with efficiency. you need a certain size in order to cool a certain amount of space effectively; too small and it never turns off, too large and it constantly turns on/off thereby shortening its life. you need a certain efficiency in order to save money.

          it's just like buying a car and choosing the right engine for it. typically a smaller engine for better fuel efficiency, while a large
      • You're right, of course... I should have double checked before posting so quickly. Multiply... Divide... Those are almost the same, right? ;)

      • Conversion factor: 1 KWH = 3412 BTU
        Multiplying the average (not peak) wattage by 3.4 will get the BTU's per hour of cooling capacity.

        That will give you the average cooling requirement, which will be exceeded when the system load increases, or when the systems are upgraded, etc.

        Go with the peak load, or bad things will happen.
        A/C units do have thermostats, you don't want to run it at its maximum capacity 100% of the time.

    • If you divide the wattage by 3 to get the BTUs/hour, the AC's going to be undersized. According to my notes, you approximate the BTUs/Hour by multiplying the power in watts by 3.41. At least that's how I calculate the numbers for my customers, when they need those figures.
    • There needs to be a hole for the A/C to go in, but the heat goes out through the A/C.
    • Put a big slow quiet fan in the top one blowing in, and an air filter in the bottom (or the other way around)?
      Definitely the other way around. Put the filter on the intake: you're trying to keep the dust out of the server closet, not inside it.

      I mean, we are routing packets and not wood here, right? :)
    • Also, if he's doing this to cut down on noise in his office, better hope nobody has to work by that closet. The sound of the AC unit could be annoying as well.

    • As long as you're going to have a vent hole anyway

      Since the OP said that the closet used to house the furnace, there's probably already a chimney anyway. If it was an old furnace it actually lost some heat out the chimney, some of the fanciest new ones have cold exhaust, but either way, there's probably a duct ~5-6" in diameter that goes to the outside. It may have been plugged or blocked when the furnace was removed, but it's probably pretty easy to get to.

      Since the servers probably don't produce all that
      • The OP didn't say what the four servers are, but if they have 300 watt power supplies, then four of them is 1200 watts, which is getting up into the toaster and hair dryer area. 1200 watts is 4092 btus/hr, more if you have monitors, hubs, switches, or even a light bulb in there. And if the AC itself is in the closet, then you have to add in the heat it generates. most little A/C units are no better than a EER of 10, so a 4000 btu/h unit will add 400 btu/h for itself. Which means you need 5000 btu/h unit. T
        • And if the OP is actually using them as servers rather than consoles, whenever the door is closed the monitors are off and the light is off. hubs and switches for in the house are going to be in the neighborhood of 20 W each.

          If the AC is in the closet it has to be one of the little mobile "local" AC units that has an exhaust vent tube that goes somewhere else to take all the heat it generates away, otherwise it's just a heater. It would be a minor violation of thermodynamics to expect the AC to exhaust th
          • I have five machines (older workstation chassis repurposed as SOHO servers) a 24-port switch, DSL gear, a couple of laptops as NOC monitoring stations, and enough UPSes to run them all, in the former laundry closet of the house we remodeled into our office. We have a high-capacity centrifugal bathroom vent fan sucking air off the top of the room and ducting it down flexible metal vent hose, and out the old dryer vent outlet. The doorway to the room is weatherstripped around the edges and we cut a 30"x3" int

      • servers probably don't produce all that much heat

        They are likely to generate a fair amount. 4 or 5 kbtu/hr. If you use a fan, and draw air through a louvered door from a conditioned space, you will be using the main A/C to cool the make up air. So the cooling costs will be about the same (depending on the efficiency of the main A/C) in terms of power cost to run the A/C. The louvers will let most of the noise back into the room, which will negate most of the sound savings. Sound travels thru very small

        • The OP may or may not have whole house AC. If there is whole house AC unit is probably more efficient and quieter than a small unit for local cooling. The small unit also has to dump its waste heat somewhere, and that's likely into the house. So now the house AC has to cool the waste heat of the little AC, which will be more than the heat of the servers.

          Louvers probably won't let that much noise back in, and a little baffling can probably take care of it if it's more than the OP wants. I've been in plen

    • As long as you're going to have a vent hole anyway, why not cut two? Put a big slow quiet fan in the top one blowing in, and an air filter in the bottom (or the other way around)?

      This is the single most sensible suggestion that has been made on this thread. Use fans.

  • For that few BTUs (Score:4, Interesting)

    by Marxist Hacker 42 ( 638312 ) * <seebert42@gmail.com> on Wednesday October 19, 2005 @05:47PM (#13830843) Homepage Journal
    I'd recommend one of these [smartbargains.com]. The twin fan design can be set to exchange, and the controls can be set to certain temperatures so that you're not wasting energy in the winter.

  • Use the heat. (Score:3, Interesting)

    by grub ( 11606 ) <slashdot@grub.net> on Wednesday October 19, 2005 @05:54PM (#13830887) Homepage Journal

    If it was used for heating at one time perhaps you could use a fan to fee the air into the ducts in the winter months (assuming your winter months are like my winter months :)) It seems counterproductive to use power to cool a hot room in the winter.

    • Re:Use the heat. (Score:3, Insightful)

      by Goyuix ( 698012 )
      Yes but what happens to those poor servers when the real heater kicks on during those winter months and cooks the whole closet? You would most certainly need to have a one-way vent of sorts.

      Of course, what if the heat stays on for a long enough period of time, and the closet can't vent... or perhaps over time, each time the furnace fires up and shuts down, the closet warms up 1 degree or so... could be disaster.

      Better to just flat out vent it to a storage room or somewhere that is can freely blow, and feed

  • We went with this package (Score:4, Informative)

    by Pacifix ( 465793 ) <zorp&zorpy,com> on Wednesday October 19, 2005 @06:03PM (#13830959)
    for a situation just a bit bigger than what you described: http://www.getcozy.com/fff.html [getcozy.com]. We like it. Here in Seattle we get quite a bit of condensation that needs to be emptied (or pumped if you want). This place also has other options you may wish to look at. Nice guys too.

  • Here's an idea (Score:1, Redundant)

    by Kraeloc ( 869412 )
    Tear out your normal furnace altogether. Then install some ducting and fans, and use the room to heat your whole house.
  • I've always want to try a winter vs. summer solution.

    In the winter, just vent the heat towards the room you spend the most time in.

    In the summer, take in air in near ground level (if not prone to floods!) and venting it up and out by convection or just out the nearest wall if fan forced. A steady flow of air, even if it's humid and 90F will keep your servers pretty happy so long as the amount of air is sufficient. A muffin fan won't be enough, but a 6'' duct fan should do the trick.

    A more "green" solution
  • What you need to do is find the specifications for your equipment. How many BTU/hr does it dissipate? The number may be variable -- more under heavy load than at idle.

    then get an a/c unit sized that big.

  • Instead of an aircon... (Score:3, Informative)

    by HotNeedleOfInquiry ( 598897 ) on Wednesday October 19, 2005 @06:10PM (#13830995)
    Consider labyrinth ducts and a forced air fan. Put the fan in the server closet, build labyrinth ducts in and out of the closet. Labyrinth ducts have been used for years to sound isolate recording studios from each other.

  • Maybe a small, portable A/C unit? (Score:3, Interesting)

    by babbage ( 61057 ) <cdevers.cis@usouthal@edu> on Wednesday October 19, 2005 @06:18PM (#13831068) Homepage Journal

    I'm assuming that the through-the-window models won't help you, but one of the portable ones might. To pick one at random, consider this portable A/C unit [sears.com]. The advantage of something like this, as opposed to the window fans [smartbargains.com] that some others have suggested, is that it should come with an exhaust hose that you can channel to either the furnace's exhaust pipes, or to some other appropriate outlet elsewhere in your home. Something like that ought do do exactly what you need here.

    • The problem with the portable units is the drip pan (for the condensation) tends to fill up during extended use causing the unit to turn off until the pan is emptied. They have a small plugged tube in the back near the bottom, this needs to run to a drain for continued use.

  • Tubwarmer! (Score:3, Interesting)

    by kfx ( 603703 ) on Wednesday October 19, 2005 @06:20PM (#13831081)
    If the closet is adjacent to a bathroom, you can do what a friend of mine did--cut a hole in the wall and pipe the exhaust heat from the closet server into the hollow area behind/beneath the shower/bathtub. Not only does his server stay nice and cool, but his wife never complains about a cold bathtub again!

    • Re:Tubwarmer! (Score:3, Funny)

      by baadger ( 764884 )
      Your sig fails to take into account the terminating null byte, or perhaps a length indicator byte.

      I do, Sir Tubwarmer, have a segmentation fault.
    • Um, can you say "mold" ?

      When that hot humid air from the server room hits the bottom of the cooler bathtub, and circulates around in there, you're going to get a nice crop of fungus growing, which will eat the wood, and ultimately, send your friend's wife, naked and wet, crashing through the floor.

      Good idea to recover the heat, but without a dessicator, you'd be better off dumping the heat into living space, where the much larger room size will help mitigate any moisture problems.

  • This might work (Score:2, Interesting)

    by Odocoileus ( 802272 )
    I'm thinking two of those clothes dryer vent things you see on houses, some of the tubing that goes with it, and some duct tape. Then just put two holes in the door and make a little distribution point so you can split the two hoses as needed for each computers input and output. That way every computer draws from, and returns to, the ambient house air. Then the computers willl be drawing fresh air, The room should stay relatively cool from this. If the room temperature were to become troublesome, then

  • A/C Unit (Score:3, Funny)

    by salmonz ( 697297 ) on Wednesday October 19, 2005 @06:58PM (#13831262)
    How about this A/C unit?

    http://www.hvacportablesystems.com/images/210airch il.jpg [hvacportablesystems.com]

  • Check the RV market.. or vent it (Score:3, Interesting)

    by i.r.id10t ( 595143 ) on Wednesday October 19, 2005 @07:05PM (#13831301)
    Check the RV market - there may be something small that won't leave you with a buttload of water to take care of as well. Of course, most of the RVers I know go the cheap route and use a small window shaker unit - under $100 at walmart, home depot, etc. Heck, I've got one to run with my generator for when the power goes out for a week like happened to me with the 'canes last year.

    Of course, you could vent it instead. Use just enough fan power (blowing into attic or out or whatever) to create a very small negative pressure - you don't want to AC the world. If you should need heat elsewhere, block off the vent, reverse the fan, and leave the door open. My dual AMD rig provides a nice 5 F. boost in the room it lives in.
  • Use an RV air conditioner. They are frequently used for cooling small cubicles. You may have seen them on the booth that the gas attendant sits in at gas stations. Of course, you'll have to comply to local building codes

  • Use the existing ductwork (Score:3, Interesting)

    by La Camiseta ( 59684 ) <me@nathanclayton.com> on Wednesday October 19, 2005 @07:38PM (#13831515) Homepage Journal
    Just put a fan on the ductwork that should still be there from the old furnace blowing the heat out through your house. Then you get the bonus that it helps heat your house in the winter, and it'll use your existing a/c to cool it all off in the summer (if it pulls in the air from under the door, and blows it out from the cieling). That way you don't have to wire in anything more complicated than a fan, and everything'll still stay nice and cool.
    • Better yet, make sure the ductwork is connected to the real (furnance/central air)'s cold air return. The excess heat will help heat the house in the winter and your furnance fan should be able to pull the needed CFM.

      The catch is making sure your furnance fan cycles even when no heating/cooling is going on, check into controlling your furnance via computer interface. One could setup the system that the furnance fan is tripped based on the server closet temp!

  • Ductless split AC system (Score:2, Interesting)

    by R2.0 ( 532027 )
    Search for it; it's what you need. Not cheap, but doing something the right way rarely is.

  • I've done this in my house... (Score:4, Informative)

    by RandomJoe ( 814420 ) on Wednesday October 19, 2005 @07:58PM (#13831655)
    My results have been so-so.

    First I tried one of the portable units. Two caveats with them:

    1. Get one that has TWO ducts, these suck in air through one to cool the condenser ("outside") coil, then blow the hot air out the other. I got one that had just one, which means it uses some of the room air to cool the condenser. Problem is, in my closet, that meant enough air was being sucked into the closet from the rest of the house that the unit effectively never shut off. Not desirable.

    2. Be careful where you vent the exhaust. Many models now have a pump that dumps the condensate over the condenser coil to help increase the cooling. This means the exhaust air can be VERY humid, and you probably don't want to just dump that into your attic. (Oops... I did that...) Especially if it's cool outside (thus the attic is cool) you may wind up with a lot of water collecting in the insulation. So vent it outside!

    I decided I wasn't happy with the way the portable worked, so I actually installed a mini-split. WAAAY too big for the room (it's 9000 btu and the room's about 6ft square) but with the application of some extra controls (I work for an HVAC controls company) I managed to keep the runtime reasonable.

    You may be able to find smaller units - some people have suggested RV units, that might work better. Just be sure to get "low ambient" options if you live where it gets below 60 degrees outside, and you expect to need it during the winter. Otherwise, you'll be replacing the compressor after the first winter. Basic low ambient items are some heat tape wrapped around the compressor and a pressure switch that cycles the outdoor fan.

    If your heat levels aren't too bad you might get away with just a bathroom exhaust vent in the ceiling. I bought a combo light/exhaust fan and replaced the closet's light. Installed a line-voltage thermostat on the wall, and now the exhaust fan comes on if the closet gets too hot. Make sure the closet door has a decent gap at the bottom to allow air in. Unfortunately, my heat load was high enough that the fan pretty much ran all the time...
  • It scares the hell out of me. I have nightmares of the A/C wearing out, allowing our 8 servers to heat up the small server room, starting a fire and taking out the building, which doesn't have ceiling sprinklers because of the other damage it'd cause if there was a false alarm. It's better than what the server room had before, nothing at all. Whoever designed the building manage to make the server room be the only room without air conditioning. It was only after months of complaining that they installed any

  • My experience (Score:4, Insightful)

    by sootman ( 158191 ) on Wednesday October 19, 2005 @09:36PM (#13832211) Homepage Journal
    I live in Florida and have a hallway closet serving as a server closet. Currently it has one PC (333 MHz AMD minitower with 4 HDs), my DSL modem, a router, and an access point. In the past it also had a 500 MHz Compaq Deskpro EN SFF (85W PS, I think) and an ancient 120 MHz full-size Compaq Deskpro.

    I keep the house at 75-80 degrees, the closet has louvered doors, and heat has almost never been a problem. I ran into an issue once when something was wrong on the AMD and it would go to 100% CPU long enough to set off the alarm on the ASUS motherboard, but other than that, all 1/2/3 machines (at various times) have been humming along for over 3 years.

    As for you, you might want to tap into the house's main AC and run a little 2-4" pipe for a bit of cooling, but that's as far as I'd go. I've had to replace a fan or two along the way, and one HD died, but that was an old (at the time) 6.8 GB IDE drive that probably had no business being in a 24/7/365 machine in the first place, so heat probably wasn't even the cause of that anyway. I haven't seen any more failures in that closet than I have with any other machine anywhere else in the house.

    Laws of thermodynamics dictate that you can't put a window unit in there or anything (assuming this closet is not against an exterior wall)--that would heat up the rest of the house. IF you need cooling, run a duct from your existing AC. If you don't have AC at all, then a couple 6"-8" fans should move enough air. Assuming you don't have an airtight closet (louvered doors highly recommended!) you could have one or two fans drawing air up through the closet and exhausting into the attic.

    Basically, think of the whole closet as being one giant computer case and plumb accordingly. And of course it wouldn't hurt to hit Radio Shack for a $20 digital indoor/outdoor thermometer to keep an eye on things.

  • I've got an idea... (Score:3, Funny)

    by Anonymous Coward on Wednesday October 19, 2005 @10:36PM (#13832527)
    why not just cram an old refrigerator in there, mod the interior to support rack gear? you could even put that overclocked celeron 300a you used to want so bad up in the freezer, running at a cool even G (1 Ghz).
    • Parent was modded funny but I think it would work. My grandpa used to keep his welding rod in an old refigerator in his shop. It kept the rod cool and dry and it could keep in there for many years without going bad. (he ran a farm equiptment repair business out of his shop in in semi-retired days)

      Moisture wouldn't be a problem, would stay cool, the machines own cooling fans would keep the air circulating and minimize hot spots.

      Plus you could keep some cans of beer in there too just because!

  • Forget AC (Score:5, Funny)

    by tsm_sf ( 545316 ) * on Wednesday October 19, 2005 @10:48PM (#13832584) Journal
    Find your nearest garden supply store that carries hydroponic gear. Now find the scruffiest employee therein. He'd be a great source of info on setting up ventilation systems in small rooms.
    • Find your nearest garden supply store that carries hydroponic gear. Now find the scruffiest employee therein. He'd be a great source of info on setting up ventilation systems in small rooms.

      Although you can probably do without the activated charcoal air filters and high pressure sodium lighting for your application.

      Oh, and make sure you don't have any male servers in the closet - you don't want them to fertilise the females.
  • If the furnace used to be in that closet then it probably had a louvered door for intake and there's probably output ductwork still run to that closet. Just tie that ductwork into the house's HVAC return and let it pull air through that closet with the bonus that the heat will get spread out evenly during winter and it'll probably be cheaper to let your heat pump work a little harder during summer than to operate an additional unit.
    • That's a VERY good suggestion. It would take minimal cost, minimal work, and probably provide the best long-term solution.

      Be sure to also put in a filter so you're not returning dirty air to the house AC.

  • Suppose that you air condition your closet to a nice and cool 20 degrees Celsius. Now suppose that it is a warm humid day, and you need to power cycle one of the servers. You open the door to the closet. All the cold air rushes out, and is replaced by warm humid air from the outside. Next thing that happens is that moisture in the warm air starts to condense out on cool surfaces ... like the casing of your computers. Not good.

    This is not a major problem in a typical computer room because opening and cl

  • sounds pretty impossible.
  • Self contained, small, low maintaince, powerful (low end units are about 1800BTUs), includes a drain line, and air filter.
    Down side is the price.

  • Super Simple (Cheap!!) solution (Score:3, Interesting)

    by TinyManCan ( 580322 ) on Thursday October 20, 2005 @07:16PM (#13840545) Homepage
    Assuming a few things about your setup, this is the solution that I would use (and have in the past).

    Get an extra ATX power supply. Doesn't need to be real powerful or anything. Then purchase a couple of computer case fans. I'd get the 5.25" kind, because they spin slower and will last longer while still putting out a decent CFM rating.

    Cut a hole about 1' from the bottom of the closet door. Mount a fan so that it blows the air in here. This is your intake. Put a filter on it if it makes you happy.

    Cut another hole about 1' above the higest piece of equipment in the closet. Mount a fan so that it exhausts the hot air from the closet.

    Connect both of the fans to your power supply and then set the power supply on a nice wood shelf. Connect power supply to the UPS that your equipment is running on.

    Given the small load that you discussed, I would think that this setup would have you totally covered. You _MAY_ need to go to two sets of intake fans, but you should never need more than one exhaust.

    Don't just set an AC in the closet, as that will actually raise the temperature.
  • Pick up an industrial electrical enclosure cooling unit. Check out Pfannenberg [pfannenbergusa.com] or Hoffman [hoffmanonline.com]. You will have to go through an industrial supply distributer who will try to screw you on cost if you explain that you are not an industrial customer.

    You are way off on your heat load calculations. You should look at the electrical service in the closet. For electronic equipment, very near 100% of the electrical power ends up as heat. If you have one outlet rated at 15 amps then figure your max heat load to be:
    15
  • Liebert has something like that, I saw one once. It was pretty confusing how it actually worked.
    It fit in a 2' square suspended ceiling, in place of a ceiling tile. It had a little output, about a 4" hose, blowing cold air.
    No unit outside the building, not a split system. Not much wiring, not much power. It was weird. Blowing cold air into a server closet I was in. It made little noise. All self contained. Low capacity. I wondered what they did with the heat. Nothing it seemed.
    Weird.
    Liebert is of c
    • I haven't seen that particular style, but it most likely works like a window unit, except the hot air that would normally go outside is being dumped in the area above the drop ceiling.

      Most buildings now use "plenum return" air, meaning there aren't return ducts to the main A/C units, they just suck air from above the ceiling. Each room has a grille in the ceiling that lets air from the room get back above the ceiling. This means the little A/C unit is effectively just dumping its heat into the air going b
      • You're right of course, I hadn't thought of that. The building I was in was a high rise, it likely was a return air plenum. So that explains it. It was sure little though.
        At home you could just get a $49 thermostatically controlled attic fan from Home Depot, that would take care of the problem of excess heat.
        Hmm. Wonder where I could find one of those little Liebert units. Have to watch for a high rise being torn down.

  • Haier (Score:2)

    by gatzke ( 2977 )

    I have crappy AC in my office, so I had to get a rigged AC system.

    Haier has one that is about 30" tall, foot deep, two feet wide, maybe $350. Best part is, it evaporates the condensate in the exhaust so you don't have a drip pan to empty (like some other portable AC units or a wall unit). You do have to vent any cooling unit, so that will always be a problem. You can't just cool a room using electricity, the work is going to generate heat somewhere and that has to be vented.
  • Stick them in a refridgerator.

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