HP rp4410 Manual page 31

• Reheating
• Air distribution
• System controls adequate to maintain the computer room within specified operating ranges
Lighting and personnel must also be included. For example, a person dissipates about 450 BTUs per hour
while performing a typical computer room task.
Air Conditioning System Guidelines
The following guidelines are recommended when designing an air conditioning system and selecting the
necessary equipment:
• The air conditioning system that serves the computer room should be capable of operating 24 hours a day,
365 days a year. It should also be independent of other systems in the building
• Consider the long-term value of server availability, redundant air conditioning equipment, or capacity
• The system should be capable of handling any future server installations, including added accessories and
additional servers and peripheral equipment
• Air conditioning equipment air filters should have a minimum rating of 45% (based on ASHRAE
Standard 52-76, Dust Spot Efficiency Test)
• Introduce only enough outside air into the system to meet building code requirements (for human
occupancy) and to maintain a positive air pressure in the computer room
Air Conditioning System Types
The following three air conditioning system types are listed in order of recommendation:
• Complete self-contained package unit(s) with remote condenser(s). These systems are available with up or
down discharge and are usually located in the computer room
• Chilled water package unit with remote chilled water plant. These systems are available with up or down
discharge and are usually located in the computer room
• Central station air handling units with remote refrigeration equipment. These systems are usually
located outside the computer room
Basic Air Distribution Systems
A basic air distribution system includes supply air and return air.
An air distribution system should be zoned to deliver an adequate amount of supply air to the cooling air
intake vents of the server equipment cabinets. Supply air temperature should be maintained within the
following parameters:
• Ceiling supply system—From 55°F (12.8°C) to 60°F (15.6°C)
• Floor supply system—At least 60°F (15.6°C)
If a ceiling plenum return air system or a ducted ceiling return air system is used, the return air grill(s) in the
ceiling should be above the exhaust area or the exhaust row.
The following three types of air distribution system are listed in order of recommendation:
• Underfloor air distribution system—Downflow air conditioning equipment located on the raised floor of
the computer room uses the cavity beneath the raised floor as a plenum for the supply air
Return air from an underfloor air distribution system can be ducted return air (DRA) above the ceiling
Chapter 2
General Site Preparation Guidelines
Environmental Elements
31