VETERANS BENEFITS ADMINISTRATION
VA REGIONAL OFFICE TECHNICAL CRITERIA
Computer Room Air Conditioning/Humidification
For redundancy and serviceability, two identical computer room air-conditioner (CRAC) units are
required. Refer to ASHRAE for temperature and humidity requirements. A ten degree per hour
change is allowable. Humidity shall be maintained at 40 percent RH, plus or minus five percent,
non-condensing. The units shall be positioned at opposite ends of the computer room (preferably
diagonally opposite) to ensure even distribution of conditioned air from both units. Both units shall
be operating at all times and sharing the load unless one fails or is undergoing maintenance.
Redundancy shall be built into the system which may be chilled water, glycol or DX cooling such
that failure of any one pump, compressor, blower or the like will not result in computer room over-
temperature. The cooling capacity of each CRAC unit should be adequate to remove all the sensible
heat from the computer room. The raised floor (12 inches high minimum) will act as the cool air
supply plenum and cool the equipment and the room using cutouts and vent tiles (quantity based on
75 percent of the system airflow with a 500 fpm velocity). The computer room and the telephone
equipment room (TER) shall be adjacent with a common raised floor so that the CRACs may also
provide cooling for the telephone switch and related equipment located in the TER. If a standby
power source is available, it should be connected, through an automatic transfer switch, to the
CRACs. For more detailed information, refer to the VBA Computer Room Design Guidelines at
http://vbahinesweb.vba.va.gov/engconse.htm.
Seismic Safety
Comply with the Uniform Building Code (UBC) and local building codes.
MECHANICAL
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