Computer rooms require precise and adaptable temperature control for several reasons:
Need for cooling. Data centers have a dense heat load, generally 10 to 30 times the heat density of normal offices.
Cooling must be delivered where needed. The heat load varies across the area of the computer room. To achieve a balanced psychrometric profile, the air conditioning system must address the needs of particular heat-producing equipment.
Data centers need precise cooling. Electronic equipment radiates a drier heat than the human body. Therefore, precision data center cooling systems require a higher sensible heat ratio (SHR) than office areas. Ideally, the cooling system should have an SHR of 1:1 (100 percent sensible cooling). Most precision systems have sensible cooling between 85 and 100 percent, while comfort systems normally rate much lower.
Controls must be adaptable to changes. The data center heat load will change with the addition or reconfiguration of hardware. Also, exterior temperature and humidity can vary widely in many places around the world. Both of these conditions will affect cooling capacities . Data center air conditioning systems must be chosen for their ability to adapt to these changes.
Data centers need frequent air exchange. To create a precision cooling environment, the air must be exchanged at an adequate rate. While a normal office environment requires only two air changes per hour, the high-density heat load in a data center requires as many as 50 changes per hour . Precision air conditioners pass more than 500 cubic feet per minute (CFM) per ton, while comfort cooling air conditions might pass as little as 350 CFM per ton. If not enough air is exchanged in a given time, the cooling air will heat up before reaching the equipment it is meant to cool, and problems could occur.
