Trane TRG-TRC014-EN Constant Air Volume to the Space, Single-Fan, Dual-DuctVAV System, period two

period two

Components of a VAV System

notes

Constant Air Volume to the Space

100%								maximum
								primary
		warm						airflow
to space		primary air
airflow								minimum
%								primary
			cool		primary air			airflow
0%
	design			space load			design
heating load						cooling load

Figure 36

To deliver a constant volume of supply air to the space in a two-fan, dual-duct system as the cooling load in the space decreases, the amount of cool primary air is reduced and the amount of warm primary air is increased, maintaining a constant total supply airflow to the space.

Because of this constant airflow to the space, no fan energy savings is realized at part-load conditions.

Single-Fan, Dual-Duct VAV System

		central air handler	cooling	55°F [12.8°C]
			coil
	OA	55°F
	40°F	[12.8°C]
	[4.4°C]		heating	105°F [40.6°C]
			coil	dual-duct
		VSD
				VAV
				terminal
EA		RA		units
		75°F
		[23.9°C]

Figure 37

Dual-duct VAV systems also have a central return-air path that allows air from the spaces to come back to the air handler. Dual-duct systems may, however, have either one or two central air handlers.

At the single air handler, a portion of the return air is recirculated and mixed with outdoor air. This mixture of outdoor and recirculated return air is then diverted through either the cooling coil or the heating coil and delivered down

24 TRG-TRC014-EN