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TRG-TRC014-EN 5
period one
What Is Variable Air Volume?
notes
The terminal reheat system uses a central air handler and cooling coil to deliver
cool primary air to all the spaces. Each space has its own heating coil to temper
the air to satisfy the space load. Of course, any heat added to meet the part-load
requirements of a space becomes a cooling load that the refrigeration system
must overcome. This can result in a nearly constant refrigeration load, even
when the building is at part-load conditions.
Therefore, reheating cooled air to achieve part-load supply air temperature
control is not very energy efficient and is used only in special constant-volume
applications, or when there is a “free” source of heat (i.e., heat recovery).
Primary air (PA) is the air delivered by a central supply fan to a terminal unit.
Supply air (SA) is the air delivered to a space.
Terminal Reheat System
EA
PA
OA
RA
supply
supply
fan
fan
cooling
cooling
coil
coil
reheat
reheat
coil
coil
thermostat
thermostat
SA
Figure 8