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TRG-TRC014-EN 47
period three
System Configurations
notes
Typically, either VAV reheat or fan-powered terminal units are used to provide
the tempering needed to balance the reduced cooling load.
Changeover/Bypass VAV System
Many smaller buildings cannot afford commercial, or applied, equipment. Often
constant-volume, light-commercial equipment, like a small packaged rooftop
unit, will be used.
Nevertheless, it may still be desirable to accommodate many independently
controlled spaces economically. For these applications, a special VAV system
called a changeover/bypass VAV system is available.
Like a typical VAV system, a changeover/bypass VAV system contains an
airflow-modulation device for each individually controlled space. This device
modulates supply airflow in response to the space load. Instead of modulating
the central supply fan, however, this system supplies constant primary airflow.
Small Buildings
Figure 65
Changeover/Bypass VAV System
EA
OA
RA
supply
supply
fan
fan
VAV
VAV
damper
damper
PA
bypass damper
bypass damper
constant
constant
-
-
volume supply fan
volume supply fan
VAV to spaces
VAV to spaces
SA
Figure 66