14 July 2004
Including changes 12 April 2005
conditioner units are suggested, connecting through the wall via a single conduit
penetration that contains the refrigerant supply and suction lines, the power and
control cables, and the condensate disposal line directly & immediately outside
the NMCI/Telecom space. Avoid running any condensate lines above the
NMCI/Telecom equipment and, if possible, keep these lines entirely out of the
space. Cassette type ductless split system evaporators, laying in suspended
ceiling systems are an acceptable, but less desirable, solution. These rely on a
condensate pump and line to convey the condensate out of the space. Where a
raised floor is provided sufficiently high enough to act as a plenum, floor-mounted
DX computer room air conditioners may be used. Pay particular attention to
sealing each penetration of the exterior wall, floor or roof, to preclude penetration
of wind-driven rain or snow. Ensure air conditioning systems are able to start
and operate at both low and high ambient outside air temperatures to maintain
the design indoor conditions.
Utilize single evaporator units with individual condenser units, to
maintain the redundancy needed. Split units are available with up to 3 or 4
suitable for homes and offices, it is not appropriate for the redundancy required
by the NMCI/Telecom rooms.
Chilled water systems, and evaporative-cooled water-glycol
systems, are discouraged in order to reduce the probability of fluid leaks and
possible damage to the NMCI/Telecom equipment in the space. If these systems
exist, and have extra capacity available, they may be used; but only if the cooling
coil units are located outside the NMCI/Telecom spaces, and the supply and
return air is ducted into and out of the space. Insulate both supply air and return
air ducts within the NMCI/Telecom spaces to prevent condensation from forming
on the ducts and dripping onto the electronic equipment.
Avoid running refrigerant lines within the NMCI/Telecom space. If
refrigerant suction lines must be run within the NMCI/Telecom space, insulate
them and run them inside of a conduit made of pvc or cpvc pipe, with cemented
joints made water-tight; also, insulate the outside of the conduit. The insulation
must be flexible cellular type. Pitch the conduit to drain outside the
Provide corrosion protection for all outdoor equipment located in
salt-laden coastal areas. Provide snow protection for all outdoor equipment
located in areas subject to heavy snow accumulations.
Design Conditions. Temperature is to be maintained at 23.8 oC
+/- 5 oC (75 oF +/- 10 oF.) No humidity control is required. Under emergency
conditions, variation of +/- 10 oC (+/- 20 oF) is acceptable.