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10 TRG-TRC014-EN
notes
period one
What Is Variable Air Volume?
There are some basic building characteristics that favor the application of VAV
systems. We will discuss three:
n Variable thermal load profiles in the spaces.
n The need for multiple, independently-controlled spaces.
n The existence of a common return air path.
A key feature of a VAV system is its ability to realize both fan and refrigeration
energy savings at part-load conditions. A building with construction and
utilization characteristics that cause the thermal load profiles of the spaces to
vary throughout the day and year is an excellent application for a VAV system.
The fact that the west-facing space in this example has a very different load
profile than the east-facing space allows the VAV system to take advantage of
this energy savings at all hours of the day.
▲ Variable thermal load profiles
▲ Multiple, independently-controlled spaces
▲ Common return air path
VAV Building Characteristics
Figure 15
Variable Thermal Load Profiles
100
75
50
25
0
100
75
50
25
0
percent space loadpercent space load
6126
6126
noon
noon
a.m.
a.m.
p.m.
p.m.
west
west
-
-
facing
facing
space
space
east
east
-
-
facing
facing
space
space
Figure 16