Trane TRG-TRC014-EN manual Single Duct, Cooling Only, Components of a VAV System, period two

period two

Components of a VAV System

notes

Single Duct, Cooling Only

primary air

supply air

Figure 22

The simplest of all VAV terminal units is the single-duct,cooling-onlyterminal unit. It consists of an airflow modulation device with controls packaged in a sheet-metal enclosure. The unit can only modulate the primary airflow to the space. The primary air is supplied by a single, central air handler.

This VAV terminal unit is typically used for those zones that require year-round cooling, like the interior zones of a building. It is the most common and basic type of single-duct VAV terminal unit.

Single Duct, Cooling Only

100%	remote source of heat			maximum
				primary
		heating	tempering	airflow
to space
airflow				minimum
				primary
%
			primary airir	airflow
0%
design		space load		design
heating load				cooling load

Figure 23

This graph indicates how the air supplied to the space by the terminal unit varies as the space loads change. The vertical axis indicates the total airflow supplied to the space. The horizontal axis indicates the space load.

The supply airflow to the space is reduced as the cooling load in the space decreases. Responding to the space thermostat, the primary airflow is modulated between maximum and minimum settings. The maximum setting is

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