if you are somewhat of a fool like me and managed to install your audi headrest in backwards then found that you are unable to pull it out, i have the solution.

The pictures below are without the headrest installed to make it easier to see.

Step1. On the side that does not have  the release button carefully pry the top cover off.

 Step 2. Remove the metal locking spring.

Step3: use the release button on the opposite post and pull the head rest out. 

Step4: Put the sprint and cover back on the same way and reinstall your headrest (hopefully in the correct direction this time)

There is not much out there to explain proper cooling calculations for a server room. I have gathered some information and broke down the calculations into a few simple steps.

 Common terms for cooling:

BTU: A Btu is defined as the amount of heat required to raise the temperature of one pound avoirdupois of water by one degree Fahrenheit. 

• 1 watt is approximately 3.4 BTU/h [1]
• 1000 BTU/h is approximately 293 W
• 1 horsepower is approximately 2540 BTU/h
• 12,000 BTU/h is referred to as a ton in most North American air conditioning applications.

The simplest way to start the calculation is to know how much power your servers will be drawing. Per server or total. A typical single cpu server will draw 1amp or 120 watt (1 amp x 120 volt = 120 watt). Dual cpu server such as Xeon or AMD will draw 2 amps or 240 watt. 

 A server drawing 120 watts will require 408 BTU of cooling (120 x 3.4). 

If you know the total amps your servers will be drawing you can use (amps x 120 x 3.4) to get total BTU required. 

 From experience i have found that on average each server uses 150 watts of power. To estimate cooling load of 100 servers multiple 100 x 150 x 3.4. 51000 BTW or 4.5 Tons (12,000 BTU in every TON). This is a bit of an over estimate but it is sufficient to cool not only the servers but UPS/Transformer and anything else typically found in a server room.

 *Note all numbers are based on estimates. The totals you receive will be close to what you expect but not exact.