Trane N512 Benutzerhandbuch

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 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%). 

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).

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