Applications Guide Tracer Graphical Programming - Trane

®
Chapter 6 VAV AHU example
Reviewing the sequence of operation
In this scenario a VAV air handler provides comfort heating and cooling to
a space. The air handler contains a variable-speed fan, both cooling and
heating coils, and an outdoor air damper. The air handler is a stand-alone
unit (Figure 104).
Figure 104: VAV air handler
Modes and setpoints
The following parameters for the sequence of operation are presented
according to the occupancy mode, the heat/cool mode, or the setpoint.
Occupied mode
The occupied mode is initiated by the Tracer MP580/581 local schedule or
by a unit override. When the air handler is in occupied mode, operate the
supply fan continuously. Keep the outside air damper at minimum position,
unless the air handler is economizing. Modulate the cooling valve,
heating valve, and outside air damper to maintain the discharge air temperature.
Unoccupied mode
The unoccupied mode is initiated by the Tracer MP580/581 local schedule
or by a unit override. When the air handler is in unoccupied mode, turn
the supply fan off and fully close the outside air damper and the cooling
and heating valves. Open the heating valve completely if the outdoor air
temperature falls below the freeze avoidance setpoint, 35°F (adjustable).
Space setpoints
For occupied, occupied standby, and occupied bypass modes, calculate
effective cooling and heating setpoints based on a single space tempera-
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