Heating/Cooling Mode Control - Trane Tracer AH540 Setup And Operation

CNT-SVX05B-EN
See Table 16 and Table 17 for an example of how the controller deter-
mines the effective discharge air temperature setpoint.
Table 16. Example of configuration parameters
Discharge-air cooling setpoint
Maximum discharge-air cooling setpoint
Minimum discharge-air cooling setpoint
Discharge-air heating setpoint
Maximum discharge-air heating setpoint
Minimum discharge-air heating setpoint
1 When the controller is applied to an air-handling unit with a draw-through supply
fan, the maximum discharge-air heating setpoint should be set to 104ºF (default set-
point). This prevents the discharge air temperature from exceeding the high temper-
ature limit of the supply fan motor. Exceeding the motor temperature limit can
cause premature failures.
Table 17. Example of communicated values
Discharge-air cooling setpoint input
Discharge-air heating setpoint input
Effective heat cool mode
Since the effective heat cool mode is cool and the communicated value has
precedence over the local configuration value, the discharge-air cooling
setpoint is 50°F. The maximum and minimum discharge-air cooling set-
point limits are then applied to determine an effective discharge-air tem-
perature setpoint of 53 °F, from Table 16.
In this example, if the effective heat cool mode is Heat, the effective dis-
charge air temperature setpoint would be 100°F.
The discharge air temperature control loop uses the effective discharge
air temperature setpoint, discharge air temperature (from the wired sen-
sor), and the configured control gains to calculate an output capacity for
the end devices.

Heating/cooling mode control

The heating or cooling control mode of the controller can be determined in
two ways:
Communicated request
•
Automatically by the controller
•
Communicated request
A building automation system or peer controller may communicate the
heating or cooling mode to the controller using network variable nviAp-
plicMode. Heating mode commands the controller to heat only. Cooling
mode commands the controller to cool only. The Auto mode allows the con-
troller to automatically change from heating to cooling or cooling to heat-
ing. See Table 72 on page 103.
Discharge air temperature control
55ºF (18.2ºC)
68ºF (20.0ºC)
50ºF (10.0ºC)
100ºF (37.8ºC)
104ºF (40.0ºC)
1
86ºF (30.0ºC)
50°F (10.0ºC)
None
Cool
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