Trane TRG-TRC014-EN Fan-PoweredTerminal Units, Components of a VAV System, period two, parallel

period two

Components of a VAV System

notes	minimum setting of the unit for the cooling mode. When warm, buoyant air is
	During the heating mode, the primary airflow must often be greater than the
	supplied from the ceiling, a certain velocity is required to effectively deliver
	it down to the occupied portion of the space. Increased airflow may also be
	needed to meet the minimum requirement for proper operation of the
	heating coil.
	VAV reheat is more efficient than the constant-volume reheat system discussed
	earlier because heat is provided at reduced airflow and only when required.

Fan-Powered Terminal Units

warm	parallel
plenum air

cool primary air

series

Figure 27

Another method that a single-duct VAV terminal unit can employ to heat a space is to mix warm plenum air with cool primary air. Because this method uses a small fan to draw warm air from the plenum and mix it with the primary air, they are called fan-poweredterminal units.

They come in two configurations, parallel and series.

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