Trane TRG-TRC014-EN manual Fan-PoweredVAV, Dual-DuctVAV, System Configurations, period three

period three

System Configurations

notes

Fan-Powered VAV

heat loss < 250 Btu/hr/ft

[240 W/m]

parallel, fan-powered VAV terminal unit

Figure 61

Similarly, fan-powered terminal units can be used in perimeter spaces that require seasonal cooling and heating.

In the heating mode, the parallel, fan-powered unit turns on a small fan as the first stage of heating. Doing so allows it to temper the supply air with the heat (of the building and lights) that is carried by the return air, rather than using “new” energy. When activated, the small fan also increases airflow to the space, improving the mixing of supply air and space air to prevent stagnation.

Series, fan-powered terminal units may also be used in this manner. They offer the added advantage of supplying constant airflow to the space in both cooling and heating modes.

Dual-Duct VAV

heat loss < 250 Btu/hr/ft	warm
[240 W/m]	primary air
	cool
	primary air

dual-duct VAV terminal unit

Figure 62

Finally, dual-duct VAV terminal units can also be used to heat and cool perimeter spaces. The specific operation of a dual-duct system was explained in Period Two.

TRG-TRC014-EN 45