Trane TRG-TRC014-EN manual period two, VAV Terminal Units, Components of a VAV System

period two

Components of a VAV System

notes

VAV Terminal Units

primary

air▲ Heating coil ▲ Filter

▲ Mixing fan

airflow modulation device

controller	supply
	air

Figure 21

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.

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