Filter
Top Products
14 TRG-TRC014-EN
notes
period two
Components of a VAV System
The simplest of all VAV terminal units is the single-duct, cooling-only
terminal unit. It consists of an airflow modulation device with controls
packaged in a sheet-metal enclosure. The unit can only modulate the primary
airflow to the space. The primary air is supplied by a single, central air handler.
This VAV terminal unit is typically used for those zones that require year-round
cooling, like the interior zones of a building. It is the most common and basic
type of single-duct VAV terminal unit.
This graph indicates how the air supplied to the space by the terminal unit
varies as the space loads change. The vertical axis indicates the total airflow
supplied to the space. The horizontal axis indicates the space load.
The supply airflow to the space is reduced as the cooling load in the space
decreases. Responding to the space thermostat, the primary airflow is
modulated between maximum and minimum settings. The maximum setting is
Single Duct, Cooling Only
primary
primary
air
air
supply
supply
air
air
Figure 22
space load
design
cooling load
design
heating load
% airflow to space
100%
minimum
primary
airflow
0%
primary air
primary air
Single Duct, Cooling Only
maximum
primary
airflow
remote source of heat
remote source of heat
heating
heating tempering
tempering
Figure 23