TRG-TRC014-EN 9
period one
What Is Variable Air Volume?
notes
Contrasting the three systems discussed in this example, the simple, constant-
volume, variable-temperature system consumes constant fan energy while
providing refrigeration energy savings at part load. However, it can only deliver
comfort to spaces with similar loads.
The terminal reheat system can serve many spaces with dissimilar load
requirements, but consumes constant fan energy and nearly constant
refrigeration energy at part load. It also uses an increasing amount of reheat
energy at part load.
On the other hand, the variable-air-volume system is capable of providing both
fan and refrigeration energy savings at part load, making it the most energy
efficient of these three systems. In addition, the VAV system can efficiently
serve many spaces with dissimilar cooling and heating load requirements.
System Comparison
constant
constant
-
-
volume,
volume,
single zone
single zone
constant
constant
-
-
volume,
volume,
terminal reheat
terminal reheat
◆
◆
Fan energy
Fan energy
savings
savings
◆
◆
Refrigeration
Refrigeration
energy
energy
savings
savings
◆
◆
Delivers comfort
Delivers comfort
to many spaces
to many spaces
efficiently
efficiently
◆
◆
Constant fan
Constant fan
energy
energy
◆
◆
Refrigeration
Refrigeration
energy
energy
savings
savings
◆
◆
Delivers comfort
Delivers comfort
to only one
to only one
thermal zone
thermal zone
◆
◆
Constant fan
Constant fan
energy
energy
◆
◆
Nearly constant
Nearly constant
refrigeration
refrigeration
energy
energy
◆
◆
Delivers comfort
Delivers comfort
to many spaces
to many spaces
inefficiently
inefficiently
◆
◆
Reheat energy
Reheat energy
increases at part
increases at part
load
load
VAV
VAV
Figure 14
