HP Integrity rx7620 Server - User Service Guide, Sixth Edition

Air Conditioning System Installation
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
Use separate computer room air conditioning duct work. If it is not separate from the rest of the
building, it might be difficult to control cooling and air pressure levels. Duct work seals are
important for maintaining a balanced air conditioning system and high static air pressure.
Adequate cooling capacity means little if the direction and rate of air flow cannot be controlled
because of poor duct sealing. Also, the ducts should not be exposed to warm air, or humidity
levels may increase.
Humidity Level
Maintain proper humidity levels at 40 to 55% 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 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.
Dust and Pollution Control
Computer equipment can be adversely affected by dust and microscopic particles in the site
environment.
Specifically, disk drives, tape drives, and some other mechanical devices can have bearing failures
resulting from airborne abrasive particles. Dust might also blanket electronic components, like
printed circuit boards, causing premature failure from excess heat and/or humidity build-up on
the boards. Other failures to power supplies and other electronic components can be caused by
metallically conductive particles. These metallic particles are conductive and can short circuit
electronic components. Use every effort to ensure that the environment is as dust- and
particulant-free as possible.
Smaller particles can pass though some filters and, over a period of time, can cause problems in
mechanical parts. Small dust particles can be prevented from entering the computer room by
maintaining its air conditioning system at a high-static air pressure level.
Other sources of dust, metallic, conductive, abrasive, or microscopic particles can be present.
Some sources of these particulants are:
• Subfloor shedding
• Raised floor shedding
• Ceiling tile shedding
These pollutants are not always visible to the naked eye. Check the underside of the tiles to
determine the presence of these pollutants. The tile should be shiny, galvanized, and free of rust.
The computer room should be kept clean. The following guidelines are recommended:
• Establish a no-smoking policy. Cigarette smoke particles are eight times larger than the
clearance between disk drive read/write heads and the disk surface.
• Locate printers and paper products in a separate room to eliminate paper particulate
problems.
Environmental Elements 189