the waste of energy can be even more significant. Reset cold
deck temperature to meet cooling requirements of the room with
the largest load or to satisfy humidity requirements. This cold
deck temperature control reduces energy consumption.
(2) Due to high energy consumption, limit these
systems to applications requiring close control of temperature
and humidity, such as hospital intensive care areas and
laboratories. When economically feasible, use heat recovered
from the refrigeration cycle in heating coils.
Variable Air Volume (VAV) Systems. Use VAV systems for
buildings with sufficient zones (11 or more zones) and load
variation to permit reduction of fan capacity for significant
periods during the day. Do not use bypass VAV systems. The
complexity of systems should be consistent with minimum
requirements to adequately maintain space conditions. For more
information, refer to Section 6 and Appendix C.
Economizer Cycle. Obtain approval of the EFD or EFA
for use of the economizer cycle. The economizer cycle should not
be used in humid climates and for spaces where humidity control
is critical, such as computer rooms. Problems have been
experienced with linkage corrosion, excessive damper leakage,
jammed linkage on large dampers, and inadequate maintenance.
Outdoor air dampers should be located away from the intake louver
and after duct transition to minimize exposure to weather and
size of dampers. Provide outdoor air dry bulb changeover rather
than enthalpy or outdoor air/return air comparator changeover.
Pars. 6.3, 8.2, 8.3, 8.4, and 8.5 provide additional information
on the economizer cycle.
With VAV systems, return or relief fans shall not be
used. An economizer should only be used when it can be designed
with gravity relief through the building envelope. Size gravity
Section 6 and Appendix C for additional information.
Duct, Pipe, and Equipment Insulation
a) Refer to NFGS-15250, Mechanical Insulation for
guidance on design and selection of insulation systems.
b) Refer to MIL-HDBK-1011/1 for special requirements
in humid climates.
Computer Programs for Load Calculation. For input
characteristics of computer programs, refer to MIL-HDBK-1190.
Use ASHRAE procedures, hourly weather data or bin method, and