Filter
Top Products
48 TRG-TRC014-EN
notes
period three
System Configurations
Any unneeded air is diverted to the return air stream, allowing individual
comfort control of the spaces.
At part-load conditions, when more of the primary air bypasses the space, the
mixture of previously conditioned primary air and recirculated return air cuts
energy use at the cooling and heating equipment. This explains the use of the
term “bypass” in the name of this system. However, due to the fan providing a
constant airflow, no fan energy savings is realized at part-load conditions.
The term “changeover” refers to how this system handles the cooling and
heating requirements of the building. The central air handler can provide either
cooled or heated primary air to the space terminal units, and it makes this
decision by periodically “polling” the spaces. Because it can only provide
heating or cooling at a given time, this system is most appropriately used for
smaller buildings that have a minimal number of incidences where heating is
required in some spaces and cooling is simultaneously required in others.
System-Level Control Modes
When designing a VAV system for a commercial application, three system-level
control modes need to be addressed:
n Occupied mode
n Unoccupied mode
n Morning warm-up/cool-down mode
System-Level Control Modes
▲ Occupied mode
▲ Unoccupied mode
▲ Morning warm-up/cool-down mode
Figure 67