Civil Engineering Reference
In-Depth Information
Fig. 8.8
Variable air volume system with series fan-powered units
The small energy consumed by low-voltage power provided for control valves and
dampers, and the power input to the variable frequency drives for supply and return
fans that can be factored in supply and return fan consumption itself are the other
sources of energy consumption (Khazaii
2012
).
8.12.6
Changeover Bypass VVT
The difference between this system (Fig.
8.9
) and bypass variable air volume sys-
tem is that in the later system each terminal unit bypasses the air individually, but in
this system bypassing is done through designated bypass variable air volume boxes.
The main air handling unit remains constant volume.
The sources of energy consumption in this type of systems are air handling unit
supply fan motor input power, return/exhaust fan motor input power, electric preheat
strip (if it is used for freeze protection instead of hot water coil) in air handling unit,
and electric reheat strip (if it is used for dehumidifi cation or heating instead of hot
water coil).
Duct air leakage, heat transfer from ducts, and effi ciency loss in water coils are
other sources that can indirectly increase the energy consumption of the system.
The small energy consumed by low voltage power provided for control valves and
dampers is the other source of energy consumption (Khazaii
2012
).
