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A Micro-A/C for a Server Closet?
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."
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 or more likely, some other (cheaper, but similar) portable AC unit with an exhaust hose from your local Wal-Mart.
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.
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...
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.
Literalism isn't a form of humor, it's you being irritating.