Volume Number: 22 (2006)
Issue Number: 6
Column Tag: Network Infrastructure
By the MacTech Magazine Editorial Staff
The A/C Problem
Providing air conditioning 24/7 for your server room is one of those invisible problems that you may not realize until it's too late. Add to it that 24/7 air conditioning involves a great deal of power consumption, so it can be a costly affair. Today more than ever, a lot of office buildings provide air conditioning only during the week, usually from 7am to 7pm. That's fine for humans. However, most of us still have cooling requirements for our server rooms that need not only 7 days a week, but need 24/7/365 as that's when there is heat generation.
Even if you put a handful of computers in a room, bad ventilation or inadequate air conditioning will melt your machines faster than a popsicle on a hot day. Bad environmental conditions in a server room can affect the life and reliability of your machines and their components. The machines might perform bizarrely, reboot, or crash altogether. Since server rooms are the lifeblood of any company, and damage costs could be very high not only in terms of replacing hardware, but also in terms of company productivity. And, as machines get faster, they've been getting hotter. So, rather than risk an IT meltdown, companies are choosing portable cooling units for their server rooms, being that they are more versatile, and can provide or supplement cooling more cost effectively.
Before you even think about air conditioning, you should think about ventilation. You can accomplish a great deal with proper ventilation. Many people don't realize that air conditioners don't actually cool the air; they are really devices that transfer heat from one location to another. As a result, you can accomplish much of the same thing by simply venting the hot air out of your server room, and letting it suck in cooler air from the rest of your office.
But there are times that you either need to supplement your air conditioning, or have focused air conditioning, and many people are finding portable A/C units a good option.
In looking around, we found a company called Sunpentown that made some of the highest efficiency portable A/C units. Specifically, we chose the WA-1010H Sunpentown (SPT) portable A/C with heater, with a 10,000 BTU cooling and heating capacity, as one such option. This unit provides cooling, dehumidifying, and fan features all in one.
All cooling units have an EER (Energy Efficiency Rating). Most people naturally believe that units with a higher EER consume less energy than units with a lower EER. But actually, EER is not necessarily a good measurement to determine energy usage, unless you are comparing the same size of unit. The EER is calculated by taking the units potential BTU's and dividing it by the total wattage consumed.
For example, let's compare two units: a 12,000 BTU unit using 900 watts with an EER of 13.33 and a 9,000 BTU unit using 900 watts with an EER of 10. Here the power usage is the same even though the 12k unit has a higher EER. Most people would choose the 12k unit, since you get more cooling for the same energy usage.
However, for our test server, we chose the SPT WA-1010H unit, with a 10,000 BTU cooling/heating capacity, and an EER of 15.5 (normally, this would be a room that you would ideally cool or heat an area up to 300sq.ft. but server rooms have a higher heat load). We compared it to an older Sharp model (model CV - P09FX) with an almost 9000 BTU cooling capacity, and an EER of 8.9.
Both units were tested in a small server "room" (about 40 square feet with 15 computing devices). Clearly, the SPT cooled quickly and efficiently, and the Sharp would take much longer to cool the room before shutting it off. Because the SPT would start and stop more often (compressors take a lot of energy to start), it actually used about the same electricity as the far less efficient Sharp.
The SPT is the better choice for the server room as it will keep your temperatures much more consistent even with the variations of heat load that tend to happen. In the end, however, if your primary goal is energy efficiency, you would want the smaller BTU capacity while maintaining a higher EER.
Finding the right cooling unit can, unfortunately, be a process of trial and error. Different server rooms will have different requirements and heat loads. The first cooling unit or solution you try, may not always be the right size. In fact, we had to test a couple of different units to find ones that best suited our test case.
Along with efficiency and reliability considerations, you need to figure out the size of the cooling unit you will need. That may seem simple enough. After all, you just have to add together all the sources of heat and find an air conditioning unit that can take care of it. But, in practice, it's just a little bit more complicated.
Apart from temperature of both the server room and the machines, you also need to keep in mind air flow and humidity factors. It is important to maintain a consistent air flow, since moving air cools faster than air that stands still. Cooling units that come with fans can help decentralize hot spots, by providing a form of forced convection. As for the humidity factor, computers operate within a wide humidity range. Avoiding condensation is the key factor here. Also remember that sometimes when air conditioning units fail, they cause leakages and spills, so you might also want to think about how you position your cooling unit as well.
While choosing an efficient cooling unit is significant, for server rooms, reliability of the unit is more important. It is therefore more advisable to go with a unit that has an auto-restart option (in the event of a power failure), and that has more than enough capacity to handle varying heat loads.
While our test was on the WA-1010, if your room is a little larger, you may want to look at the WA-1300E, a newer model from Sunpentown that comes with the Restart IC feature. This model has a cooling power of 13,000 BTU, and is designed to cool an area of up to 420 square feet, has 3 fan speeds, and larger casters. Apart from these features, the WA-1300 E shares similar features as the WA-1010 units, such as:
Both of these models are great products, and will do a good job cooling your server room. Make sure to take into account where you are going to vent, and that you have enough power in the room to run these devices.
For detailed specifications, you can check out the following URLs on the Sunpentown website:
The SPT WH-1010H retails at $450 and the WH-1300E model retails at $569.
MacTech Magazine Editorial Staff
