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TRG-TRC014-EN 7
period one
What Is Variable Air Volume?
notes
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:
That is, 920 cfm [0.43 m
3
/s] of 55°F [12.8°C] supply air.
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,
Air Conditioning Clinic TRG-TRC014-EN
Air Conditioning Clinic TRG-TRC014-EN© Amer ican Standard Inc. 2001
VAV–Part Load
20,000 Btu/hr
1.085 × (75°F – 55°F)
Supply
Airflow
=
920 cfm
=
5,862 W
1,210 × (23.9°C – 12.8°C)
Supply
Airflow
=
0.43 m
3
/s
=
Figure 11
Supply Airflow
20,000 Btu/hr
1.085 75°F55°F–()×
----------------------------------------------------------
920 cfm==
Supply Airflow
5,862 W
1,210 23.9°C12.8°C–×
----------------------------------------------------------------
0.43m
3
S⁄==
▲ Reduced fan energy
▲ Reduced refrigeration energy
Why VAV? Energy Savings
Figure 12