Trane TRG-TRC014-EN manual VAV-PartLoad, Why VAV? Energy Savings, What Is Variable Air Volume?

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What Is Variable Air Volume?

notes

VAV–Part Load

Supply	=		20,000 Btu/hr	=	920 cfm
			1.085 × (75°F – 55°F)
Airflow
Supply			5,862 W		3
Airflow	=	1,210 × (23.9°C – 12.8°C)			= 0.43 m /s
© American Standard Inc. 2001							Figure 11
						Air Conditioning Clinic TRG-TRC014-EN

However, at part load, the VAV system produces a balance by modulating the volume of constant 55°F [12.8°C] supply air.

In this example, the air volume required to balance the lesser 20,000 Btu/hr

[5,862 W] space sensible load is:

Supply Airflow =		20,000 Btu/hr		920 cfm
		1.085-----------------	⋅-----(--75-------°---F-----–-----55------°---F----)=
	Supply Airflow =		5,862 W	= 0.43m3⁄ S
		1,210-----------------	⋅-----23.9------------°---C-----–-----12.8------------°---C--

That is, 920 cfm [0.43 m3/s] of 55°F [12.8°C] supply air.

Why VAV? Energy Savings

▲Reduced fan energy

▲Reduced refrigeration energy

Figure 12

Why VAV?

One reason to use a VAV system is the potential for part-load energy savings.

The part-load energy savings inherent with the VAV system are twofold. First,

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