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Chapter 2 Environmental and Electrical Specifications 2-3
2.1.2 Ambient Relative Humidity
Ambient relative humidity levels between 45 percent and 50 percent are the most
suitable for safe data processing operations. Most data processing equipment can
operate within a fairly wide environmental range (20 percent to 80 percent), but the
optimal goal should be between 45 percent to 50 percent for the following reasons:
■ Optimal range helps protect computer systems from corrosivity problems
associated with high humidity levels.
■ Optimal range provides the greatest operating time buffer in the event of an air
conditioner control failure.
■ This range helps avoid failures or temporary malfunctions caused by intermittent
interference from static discharges that might occur when relative humidity is too
low.
Electrostatic discharge (ESD) is easily generated and less easily dissipated in areas
where the relative humidity is below 35 percent. ESD becomes critical when
humidity levels drop below 30 percent. The 5 percent relative humidity range might
seem unreasonably tight when compared to the guidelines used in typical office
environments or other loosely controlled areas. However, it is not as difficult to
maintain in a data center because of the high efficiency vapor barrier and low rate of
air changes normally present.
2.2 Electrical and Cooling Specifications
This section provides guidelines and requirements for cooling the midrange servers.
See
TABLE 2-2 for the electrical and cooling specifications.
Be aware of the following server cooling rules and guidelines:
■ The room should have sufficient air-conditioning capacity to support the cooling
needs of the entire server.
■ The air-conditioning system should have controls that prevent excessive
temperature changes.