Civil Engineering Reference
In-Depth Information
Fig. 8.9
Changeover bypass VVT
8.12.7
Fan Coil Units
In this system (Fig.
8.10
) a separate fan coil unit or unit ventilator (including a
fan, fi lter, cooling coil, and heating coil if it is needed) is located in each zone.
Central heating and cooling plants provide required heating and cooling for the
respected coil (chilled water, hot water, or steam). Basically the unit supplies a
constant quantity of conditioned air to the zone and the coils control valves modu-
late to meet the varying load. In large systems, dedicated outdoor air units will
deliver preheated or precooled outside air through a network of ductworks to the
mixing air plenum installed in the back of the fan coil units, which mixes this
outside air with the return air from the room before moving the mixed air through
the fan coil fan.
The sources of energy consumption in this type of systems are fan coil unit
supply fan motor input power and electric heat strip (if it is used instead of hot
water coil) in fan coil unit. Duct air leakage, heat transfer from ducts, and effi ciency
loss in water coils are other sources that can indirectly increase the energy con-
sumption of the system. The small energy consumption made by low voltage
power input for the control valves and dampers is the other source of energy
consumption (Khazaii
2012
).
