Trane TRG-TRC014-EN manual VAV Reheat, primary air, Components of a VAV System, period two

period two

Components of a VAV System

notes

VAV Reheat

primary air

	terminal
	heating coil
supply
air	Figure 25

VAV reheat terminal units provide supply-air tempering or space heating by reheating the cool primary air. This is accomplished by adding an electric, or hot-water, heating coil to the discharge of a cooling-only unit.

The VAV reheat terminal unit is typically used for those zones that require seasonal cooling and heating, such as exterior zones of a building.

VAV Reheat

100%	heating coil active		maximum
			primary
	heating	tempering	airflow
space
			minimum
to			heating
airflow			airflow
			minimum
%
		primary air	cooling
			airflow
0%design	space load		design
heating load			cooling load

Figure 26

In the cooling mode, the unit is controlled in the same manner as the cooling- only unit. The supply airflow is reduced as the cooling load in the space decreases. When the space cooling load drops below the minimum primary airflow setting for the unit, overcooling the space, the heating coil warms (tempers) the primary air to balance the low space cooling load. When space heating is required, the heating coil further warms the primary air to satisfy the space heating load.

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