Trane Zone Controller Video Game Controller User Manual


 
Chapter 5 Sequence of operations
38 CNT-SVX07C-EN
Zone temperature control
The Tracer ZN521 zone controller uses two methods of zone temperature
control:
Cascade zone control—used in the occupied, occupied bypass, and
occupied standby modes
Simplified zone control—used in the unoccupied mode
Cascade zone control
Cascade zone control maintains zone temperature by controlling the dis-
charge air temperature to control the zone temperature. The controller
uses the difference between the measured zone temperature and the
active zone temperature setpoint to produce a discharge air temperature
setpoint. The controller compares the discharge air temperature setpoint
with the discharge air temperature and calculates a unit heating/cooling
capacity accordingly (see Figure 18). The end devices (outdoor air damper,
valves, etc.) operate in sequence based on the unit heating/cooling capac-
ity (0–100%).
Figure 18. Cascade zone control
If the discharge air temperature falls below the Discharge Air Control
Point Low Limit (configurable using the Rover service tool) and cooling
capacity is at a minimum, available heating capacity will be used to raise
the discharge air temperature to the low limit (see “Discharge air temper-
ing” on page 39).
Simplified zone control
In the unoccupied mode, the controller maintains the zone temperature
by calculating the required heating or cooling capacity (0–100%) accord-
ing to the measured zone temperature and the active zone temperature
setpoint. The active zone temperature setpoint is determined by the cur-
rent operating modes, which include occupancy and heat/cool modes.
Active zone
temperature
setpoint
Difference
Calculated
discharge air
temperature
setpoint
Calculated unit
heating/cooling
capacity
Measured
zone
temperature
Measured
discharge air
temperature
Difference