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TRG-TRC014-EN 13
period two
Components of a VAV System
notes
VAV Terminal Units
A VAV terminal unit is a sheet-metal assembly installed upstream of its
respective space diffusers. The unit consists of an air-modulation device,
control hardware and, depending on the system application, possibly a heating
coil, a filter, and a small terminal mixing fan. Modulating the airflow to each
individual space is accomplished using a temperature-controlled mechanical
device that varies the airflow resistance in the supply duct to that space. The
rotating blade damper changes airflow resistance by rotating the damper
into the air stream, restricting the size of the air passage to the space. It is very
cost-effective and flexible. Typically, either a pneumatic or electric controller
can be used to adjust the damper. An understanding of the common VAV
terminal unit types is important to understanding VAV systems.
VAV Terminal Units
primary
primary
air
air
supply
supply
air
air
airflow
airflow
modulation
modulation
device
device
▲ Heating coil
▲ Filter
▲ Mixing fan
controller
controller
Figure 21