Trane TRG-TRC014-EN manual Space Heating with a VAV System, Components of a VAV System, period two

period two

Components of a VAV System

notes	determined by the design cooling load of the space and the minimum setting is
	normally determined by the space ventilation requirement or minimum airflow
	for proper diffuser selection.
	Most cooling-only units are applied to spaces that have no need for heat. These
	units would operate in the region on the right-hand portion of this chart,
	modulating between design and minimum primary airflow. When cooling-only
	units are applied to spaces that do have heating requirements, the heat is
	provided by a remote source such as finned radiation along the wall. In these
	spaces, when the cooling load drops below the minimum airflow setting for the
	unit, overcooling the space, the remote heat source activates. When space
	heating is required, the remote heat source satisfies the space heating load.
	Most terminal unit controllers provide an output signal to control this remote
	source of heat.

Space Heating with a VAV System

terminal
mixing fan	plenum air

remote

heatingheat source coil

Figure 24

In addition to controlling this remote source of heat (perimeter baseboard radiation, in this example), single-duct VAV terminal units can directly provide heat to a space. This can be accomplished by adding a heating coil to each cooling-only unit or by mixing the primary air with warm plenum air before it is delivered to the space.

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