Site Preparation Guide, Second Edition - HP Integrity cx2620 Server

Above ceiling ducted air distribution
system
Supply air is ducted into a ceiling diffuser system from
upflow air conditioning equipment located in the computer
room or from an air handling unit (remote).
Return air from an above ceiling ducted air-distribution
system can be DRA above the ceiling or CPRA.
Adjust the supply air diffuser system grilles to direct the
cooling air downward around the front of the server
cabinets. The supply air is then available near the cooling
air intake vents of the server cabinets.
Air Conditioning System Specifications
All air conditioning equipment, materials, and installation must comply with any applicable
construction codes. Installation of the various components of the air conditioning system must
also conform to the air conditioning equipment manufacturer’s recommendations.
Air Conditioning Ducts
Ensure that the air-conditioning duct work in the computer room is separate from the duct work
used for the rest of the building. If the computer room duct work is not separate from the rest
of the building, it might be difficult to control cooling and air pressure levels.
Humidity Level
The recommended humidity level is between 40 and 55 percent relative humidity (RH). High
humidity causes galvanic actions to occur between some dissimilar metals. This eventually causes
a high resistance between connections, leading to equipment failures. High humidity can also
have an adverse affect on some magnetic tapes and paper media.
CAUTION: Low humidity contributes to undesirably high levels of electrostatic charges. This
increases the electrostatic discharge (ESD) voltage potential. ESD can cause component damage
during servicing operations. Paper feed problems on high-speed printers are usually encountered
in low-humidity environments.
Low humidity levels are often the result of the facility heating system and occur during the cold
season. Most heating systems cause air to have a low humidity level, unless the system has a
built-in humidifier.
Electrostatic Discharge (ESD) Prevention
Static charges (voltage levels) occur when objects are separated or rubbed together. The voltage
level of a static charge is determined by the following factors:
• Types of materials
• Relative humidity
• Rate of change or separation
Humidity Levels Influence the Creation of Static Charges
Table 2-1 compares the static charges generated by different activities in different humidity levels.
Environmental Elements 35