Heating And Cooling Changeover Logic - Trane Tracer ZN.520 Manual

Sequence of operation

Heating and cooling changeover logic

The Tracer ZN.520 zone controller can receive communicated requests for
heating or cooling operation. The communicated variable nviApplicMode is
used to communicate the requests for the controller's operating mode based on
the following values:
I 0 = Auto (mode determined by controller)
I 1 = Heat (uses heating setpoints)
I 2 = Morning Warm-up
I 3 = Cool (uses cooling setpoints)
I 4 = Night Purge (air changeover)—not supported
I 5 = Pre-cool (morning cool down)
I 6 = Off (no unit operation allowed)
I 7 = Test (special test mode)
I 8 = Emergency Heat—not supported
I 9 = Fan Only (no heating or cooling allowed)
All other enumerations will be interpreted as Auto.
In addition, the controller can receive heat/cool request inputs from
communicated nviHeatCool. The relationship of nviApplicMode and
nviHeatCool and the result of the controller's heat/cool operating mode is
defined in Table 70 on page 103.
As the controller automatically determines its heating or cooling mode, it
changes from cool to heat or from heat to cool, when the error (integrated over
time) between the active setpoint and the space temperature is (900°F • sec).
Integration begins only when the heating and cooling capacity is equal to 0% or
the discharge air temperature is being limited by the discharge air temperature
control limits. Refer to Figure 5.
Figure 5 Heat/cool changeover logic
54
CNT-SVX04A-EN