MIL-HDBK-1191
initial design, the Government and the designers shall jointly
determine the extent of system and equipment capacity increases
required.
19.4.2.5
Distribution Zone Accessibility. The available vertical
space clearances within the distribution zone shall be sufficient to
permit the organization of the utility distribution systems for easy
accessibility. It may not be practicable to arrange the distribution
zone for complete accessibility to every component. However, it is
important to examine the various accessibility requirements in order to
best locate access aisles for primary accessibility to all main
systems, feeders, connections and maintainable equipment.
19.4.3
Systems Module Mechanical and Plumbing Considerations.
19.4.3.1
Riser Locations. Risers and vertical circulation elements,
not located in the utility pods, shall be located at the boundaries of
the Systems Modules adjacent to permanent structural elements, stairs
or elevators.
19.4.3.2
Valves. Control valves, except those required to be in the
occupied zone such as medical gas control valves, should be located in
the utility pod to permit centralized control. Shutoff valves located
in the distribution zone should be tagged and identified on a valve
list that shows their distribution zone locations and the areas or
equipment served in the occupied zone.
19.4.3.3
Systems Expandability. Prime moving equipment, i.e.,
pumps, fans, etc., shall be selected with conservative judgment and the
distribution systems sized for expansion capability. In general, air
handling units and pumps should be selected for operation at the
midpoint of their operating characteristic curves. Ducts and piping
should be sized to permit future flow increases. Stubs, valves and
caps shall be provided in plumbing risers and in horizontal branch
terminations for future service extensions.
19.4.3.4
Air Handling System Selection. System selection shall be
based on functional needs, life cycle cost analyses, energy efficiency
and ease of maintenance and repair. To enhance maintainability, it is
normally desirable to "standardize" the size of air handling units when
practicable from a performance standpoint. For example, several air
handling units of the same unit size and motor horsepower, i.e., a
modular design, will allow economy in the stocking of spare parts.
"Off-the-shelf" packaged air handling units should be selected in lieu
of custom manufactured units to assure parts availability and ease of
future modification.
19.4.3.5
Ventilation of Distribution Zone. Under normal conditions,
the distribution zone will not require fresh air ventilation. However,
if so determined by the designers, ventilation may be required for
moisture or temperature control in distribution zones exposed to
roofs. A means of purging the distribution zone of smoke and other
products of combustion shall be provided.
19-5
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