The calculations below are a rough guide only. They are adequate for price comparison but before getting a cooling system installed, installer should evaluate the room to give you an exact figure.



Step 1: Standard Cooling Needs

Server room air conditioning is measured in British Thermal Units (BTUs). Calculation is merely a matter of evaluating how much heat is generated in each of several categories, adding up the numbers, and matching it with at least that much cooling.

Room BTU: Any room requires cooling based on its dimensions to reflect normal heat coming in from other areas. Multiply the area of the room in square feet by 31 BTUs.

Equipment BTU: Add up the wattage of all equipment in the room that will be on all the time, including servers and routers. Multiply this by 3.5 to get the BTUs needed. To be fair, the wattage rating of equipment is the maximum wattage and the equipment generally draws less power than this, but it is better to overestimate than underestimate.

Lights BTU: Lights are less efficient users of energy than equipment and put out more heat. Add up the wattage of all lights in the room, but multiply by 4.25 to get the BTU requirements.

Step 2: Optional Cooling Needs

The above are the standard figures all servers need. Dedicated server rooms probably won't need these other categories, but makeshift rooms often do.

Occupant BTU: Each person who works in the room will require 400 BTUs of cooling.

Window BTU: Windows are poor insulators however it is very hard to calculate exact values for how much heat loss you will get. Rather than make this section as difficult as the rest of the calculation combined, use an average of 60 BTUs/square foot of window area. If the window has no blinds, then use 100 BTUs/square foot.

Step 3: Total It Up

Add up the BTU requirements in each category to get your total server room air conditioning needs. This is the minimum amount of cooling the room will need.

Let's consider a small, ad-hoc server room as an example. We have a 10'x10' room with 1000 watts of equipment, 200 watts of lighting, one full-time worker, and a 3'x3' window with a blind in one wall.

Room BTU = 10 x 10 x 31 = 3100

Equipment BTU = 1000 x 3.5 = 3500

Lighting BTU = 200 x 4.25 = 850

Occupant BTU = 1 x 400 = 400

Window BTU = 3 x 3 x 60 = 540

Total BTU = 3100 + 3500 + 850 + 400 + 540 = 8390 BTUs

By following these guidelines, you can create a server room that is designed to protect your critical equipment and keep it functional for years to come. If these equations may seem overwhelming, a portable air conditioning specialist will normally perform the calculations at no cost before recommending the right type of unit for your server room.