Need Help with Server Closet in Home Addition!
I am looking for some help in deciding what to do with a server closet I have in my San Diego, California home. This server closet has one half-height rack in it. I read a number of posts in the forum and am not clear what I should do.
First, in terms of cooling needs, I estimate just over half a ton. Here is how I came up with that figure. The rack has two Dell servers (4,600 BTUs/hour), a switch, modem, and hardware firewall box (estimated total 400 BTUs/hour), and an APC rackmount UPS with two additional battery packs (estimate 300 BTUs/hour since the UPS usually acts like a power strip). I also have a printer sitting on its own stand that generates 1,200 BTUs/hour in the closet. All total I have 6,500 BTUs per hour.
The closet is part of a 380 square foot, one-story room. The closet itself is 12 feet long by 3 feet wide by 9 feet tall. In addition to the server rack I have three metal file cabinets (two in one corner, one in the other). The closet has two sets of double-doors, (4 total doors), all 8 feet high. We installed a 150 cfm bathroom fan in the ceiling above the back of the rack. The fan is connected to a thermostat and turns on when the closet temperature exceeds 80 degrees. The main part of the 380 square foot room is cooled by a dedicated 2-ton Fujitsu Halcyon heat pump. I have such a large unit for the room to take care of the server closet's cooling needs.
Now for my problem. Unless I open all the doors to the closet, the temperature in the closet can rise to 85+ degrees. I am concerned that once summer hits, the temperature could exceed 90 degrees. I do not want to leave the closet doors open because of the noise and aesthetics. I also cannot install a separate AC unit for the closet. The 2 ton Fujitsu needs to provide all the cooling.
I have been getting conflicting advice. Several people including my HVAC person said the 150cfm exhaust fan is likely pulling far less air when the doors are closed. He suggested I open up vents in the bottom of my doors to allow more air into the closet (so the fan would be more effective). I have also been told to look into Middle Atlantic's Quiet-Cool closet cooler (http://www.middleatlantic.com/rackac/cooling/qcool.htm). It has two vents, one that installs at the bottom of the door and another that installs at the top of the door. The bottom vent has an active 50 cfm fan that pulls cool room air into the closet. The top vents has another 50 cfm fan that blows hot closet air out into the main room. Other options include installing one or more fans in my rack to blow air through the rack (http://www.middleatlantic.com/rackac/cooling/uqfp.htm), and installing a second 200 cfm exhaust fan in the other end of the closet that would vent to the outside.
Can anyone tell me which way would be the best alternative? I tried to paint a complete picture, but please let me know if you have any questions.
Try this CFM x 1.08 x Delta T air = BTU hr.. So if your room is 85 and you are pulling 150 cfm thru it (exh) and the entering temp is the temp of the rest of the house, say 72. Do the math 150 x 1.08 x 13 =2106 btu/hr. You are half way there. Ken
one other important factor is humidity!
Originally Posted by CoolinSD
make sure the humidity does not get to low or to high!
50% is a good level to keep the humidity!
Have you thought of water cooling the srevers themselves
you get a double wammy there cooler closet and cooler longer lasting faster servers.
I remember my first day,It was fun!
Originally Posted by scottsacavsfan
I have not thought about this because I assumed it would be way beyond my budget. Is this something that is easy to do for existing servers? My two servers are pedestal design (not rackmount). They are laying on their sides on a rack shelf. Do you know how much it would cost to do this?
Thanks for the suggestion and help!
Originally Posted by Airmechanical
Thank you for the input. I never thought to monitor for this. I currently have temperature sensors, but will look into sensors that also track humidity.
Originally Posted by joken
Thank you for the formula!! When I saw your message my HVAC person happened to be on-site. He verified your math.
Based on your input, I am going to eliminate the closet cooler from mid-Atlantic. Those systems are only 50 cfm. I would need to install four of them, at a cost of over $2,000, to get the airflow I need. Instead I plan to add a fan to the server rack and monitor the situation. If the room continues to get too hot, I will add a second external exhaust fan with 200 cfm at the other end of the closet.
I assume by installing a bath fan in the ceiling of the closet that the air from that fan is exhausting into the attic or through a roof vent. If so, you're not only not moving enough air through that closet, especially with the doors closed, but you're exhausting air conditioned air from the room and creating somewhat of a negative pressure situation if you don't have a controlled make-up air source.
Short of dedicating a supply drop or unit to the closet, you're probably better off ditching the bath fan and coming up with a way to vigorously circulate air between the closet and the room. You need air exchange to happen in that closet so cooler air entering the closet will absorb heat, be expelled, then find its way to the a/c to have its heat removed and dumped outside. If you are closing the closet doors while you run the bath fan, how is air getting inside the closet, except through the small gaps under and around the doors?
To keep the equipment in the closet sufficiently cool will require the dedicated 2 ton a/c to keep the 380 square foot room considerably cooler than human comfort range, say 65 degrees, with about 300 CFM flowing through the closet. You could install a section of round duct with a duct booster fan blowing room air into the closet from a low spot in the wall, but it must be able to exhaust as much air out the top of the closet and back into the room. That could be done with return grills and boxed in sections of the wall. Trick would be to do it all without creating undue noise.
Building Physics Rule #1: Hot flows to cold.
Building Physics Rule #2: Higher air pressure moves toward lower air pressure
Building Physics Rule #3: Higher moisture concentration moves toward lower moisture concentration.
Cool, Just thinking out loud here. If you exhaust, the air has to come from somewhere. It has to come from outside and unless you create a path for it to enter it will come in around can lites etc. Here is what I would consider. You could install a air to air heat exchanger. Or, I would consider supplying air from the room with the 2 ton mini-split and exhausting it back into the same room. IF it can be done without compromising the livability of the space. Ken
I remember my first day,It was fun!
Originally Posted by CoolinSD
get a digital one!
better yet get a humidifier from home depot they have digital readouts on them
i would get the big one that way you would only need to refill maybe once every week or 2 or 3
We have successful done this.....
We have a customer with a 25U APC netshelter, fully loaded, about 750W of power consumption by the meter on the UPS, with a 10K BTU portable A/C in a server closet which is 46 x 48 inches.
From what I have seen online many have tried this and failed. We have figured out how to make this work so that the temps and humidity are within industry guidelines.
There are several things you need to address to make this work.
1. The A/C and the Server Rack need separate plugs, and both need dedicated grounds, if you don't have a dedicated ground on the a/c plug you risk sending a huge EMF pulse thru the neutral/ground which tends to wipe out hardware and raid datasets. The Server rack needs a dedicated ground otherwise the A/C will tend to cause the UPS to kick in for a second when the A/C compressor cuts in.
2. You need to use a portable a/c that does not require a drain, they exist and they have 2 exhaust tubes on them, one for hot air exhaust and one for fresh air which is used to cool the a/c components. These air conditioners get rid of the condensate by dripping across the cools, so the condensate ends up as evaporate in the hot air exhaust.
3. you Need to install a register vent in the ceiling, otherwise humidity will build up. Have openings set about 50 percent but not point straight (so there is some air resistance). This is critical, it may not seem important but humidity is about pressure, and this provides a place for air pressure to go. Without it the humidity in the air just builds up.
4. Portable a/c units have thermostats that are only accurate within 2-5 degrees at best, so don't rely on exact settings on the unit, use an separate digital therometer on the back wall in server closet as your guide.
5. The exhaust duct has to be insulated, this is most critical, without it the a/c will run longer than it should and will tend to create dangerous air conditions during outside air temperature extremes. The reason this happens is there little free standing air surround the duct, so the hot air from the duct will radiate from the duct affecting the a/c units temperature sensor. Trust me on this, this is probably the single most item that causes the portable A/c unit approach to fail.
6. Don't vent the hot air exhaust into cieling space, vent it outside, this may seem a reasonable shortcut but all you are doing is adding stress and work to building HVAC units, and you are often raising the humidity of the building, and your putting humidity where is does not belong, which can cause mold to form leading to a sick building and potentially a mold problem that can be expensive to solve, often more expensive than the building itself. The other after affect of vending into the cieling space is your re-introducing some of the humidity into the ambient air which eventually reaches the server close, over time it will raise the humidity levels in the server closet.
7. Install 2 Fan trays (the ones with 9 fans each) in the rack one at the top of the rack and the other about 1/3 up from the bottom. You need 2U blank spaces above and below each fan tray (thus 5U each consumed in your rack). This is important, not only does it protect the hardware from overheat if the A/C is off from a powerfailure (we found in this mode it limited the ambient rack inside temp to about 84 degrees F, hot but not enough to cook electronics. During normal operation the fans will draw the ambient air into the rack from the bottom, without you would have to set the portable A/C at settings provide more cooling, and humidity becomes a problem. So these fans provide the balance to cause the a/c unit to not to need to run long enough that it adds too much humitidy.
Our experience from this is humidity runs between 30-50% typically).
Investing in an enviromental monitor is a wise investment when doing a server closet.
If anyone wants pictures of our installation which works please let me know, for $25 i would be glad to provide pictures of how its done.