I work for a large company doing programming work. I have never gotten to see the inside of our datacenter until my roommate’s brother (who also works here in IT) produced a video survey of the entire network of racks, etc.
Well I’m a tech geek, so I own and operate about 30 computers, but cooling has become an issue… mostly from my rack servers (which also make a ton of noise)… so I was thinking about sticking them in a closet.
My roommate used to grow pot in this closet (not illegal, she has a grower’s permit), so there is a vent up into the attic, and there is a hatch to the crawlspace under the house from there (also vented to bring in cool air).
Well anyway, to the point… I have many loud and hot servers in my home office that I want to put into the closet and was thinking this would be ideal since there is much airflow due to the holes in the floor and in the uptake in the attic. I have questioned whether I should put in an A/C unit, since I don’t have that much hardware. But it got me to thinking about the way datacenters handle heat.
Are they enclosed systems with cooling, or does fresh (cooled) air come in while bad (hot) air expelled? Or is it just a closed system like the A/C just cooling the hot air (and thus expelling the hot air outside)?
I used to work as an HVAC engineer specializing in data center cooling. It’s been a few years since I have been in the industry.
Most of the air is recirculated in a data center. Some of the air is not. It is a legal requirement that some fresh outside air is brought into the room for safety reasons. As I recall, this is 15 cubic feet per minute multiplied by the maxumum expected occupancy of the center. Generally, this is a small amount because data centers will only have a few people in them at any time. This would be a much larger number for an office building or restaurant.
Something like 90% of the energy usage in a data center is for the cooling, not the equipment. If it is cold outside, an economizer will be used. This means that more outside air will be brought in to save on cooling costs.
Another important factor for conditioned air is the humidity. If the air is too dry you will have problems with ESD (static electricity) and will have to add humidifiers. Too much humidity is a problem too but when you cool the air, you automatically dry it so you get dehumidification for free. If the data center is in an area that can have a very humid climate, you have to put plastic in the walls so that moisture is not sucked in from the outside which would cause rain in your data center.
Another thing to consider is the hot aisle/cold aisle concept. The average temperature in the room may be 65 degrees, but there may be localized pockets of hot or cold air if equipment is placed in a random fashion.
Ideally, your rows of racks will alternate directions, creating aisles with cold air and hot air. So one row will have the fronts of the servers on each side facing the center of the aisle, and the next aisle will have the backs of the servers facing each other. Since the front side of the server is where the air intake fans sit, you can put vented/perforated tiles in that row (assuming a raised floor) so cold air from under the floor can be pushed into that aisle. The rear side of the rack will exhaust hot air, so they can face each other or face the wall (where your intake vents would be). So the rows would look like this:
| H > C < H > C < H |
| H > C < H > C < H |
| H > C < H > C < H |
| H > C < H > C < H |
| H > C < H > C < H |
This will make the most effective use of your A/C, getting cooling to the places where you need it, and removing hot air from the significantly hotter parts of the data center.
So for your particular situation, if you can direct your cold air to the front of the servers, and vent the hot air from the rear of the servers upward, that will make more efficient use of the setup that you have. You can probably make some ductwork using cardboard to guide the hot air from your equipment directly to the vent in the ceiling, if you’re really serious about it.
Well if it makes any difference, I have enough spare parts to make 30 computers!
I think I’m going to put in the ducting as you suggest from the back of the machines (they are in a server rack) that vent into the attic. There is an existing fan there already, but I might beef it up a bit by putting in something a bit larger. The cooler air from underneath the house is my only concern… I’m hoping it won’t introduce too much dust into the machines. I will try this setup for a bit and see if it works. If not, I’ll consider buying an AC unit to put into the closet (though I can see that solution getting expensive).
