Trane Tracer VV550 - Page 20

20 CNT-SVX17G-EN
Inputs and Outputs
When the hardwired setpoint adjustment is used to determine the setpoints, all unit
setpoints are calculated based on the hardwired setpoint value, the configured setpoints,
and the active mode of the controller.
For example, Table 12 shows the derivation of effective setpoints from default values and
a setpoint input.
Table 12.Example effective setpoints
Configured setpoints Default value Effective setpoint
Unoccupied cooling setpoint 85°F 85°F (same as default)
Occupied standby cooling setpoint 76°F 77°F (default + 1°F = 77°F)
Occupied cooling setpoint 74°F 75°F (default + 1°F = 75°F)
Occupied heating setpoint 70°F 71°F (default + 1°F = 71°F)
Occupied standby hea
ting setpoint 66°F 67°F (default + 1°F = 67°F)
Unoccupied heating setpoint 60°F 60°F (same as default)
Steps to calculate default values to effective setpoints:
1. Mean setpoint = (Occupied cooling setpoint + Occupied heating setpoint) / 2.
2. Absolute setpoint offset = Setpoint inp
u
t (73°F) – Mean setpoint.
3. Effective occupied setpoint = Absolute setpoint offset + Default setpoint.
4. Effective unoccupied setpoints are the same as the defaults.
The controller determines the effective space setpoint based on the following:
• Hardwired thumbwheel setpoint input (SET);
• The hardwired setpoint calibration (configured);
• Whether or not the local hardwired thumbwheel can be used or not (configured);
• Communicated setpoint input;
• Default setpoints (configured);
• Occupancy mode;
• Heating or cooling mode (space demand);
• Space setpoint high and low limits (configured).
The controller reports the setpoint it is using in the network variable output effective
setp
oint. The
controller reports the calibrated hardwired thumbwheel setpoint using the
network variable output setpoint.
When a building automation system or other controller communicates a setpoint to the
contr
o
ller, the controller ignores the hardwired setpoint input and uses the
communicated value. The exception is when the system is in unoccupied mode and the
controller always uses the stored default unoccupied setpoints.
After the controller completes all setpoint calculat
io
ns, the calculated occupied setpoint
is validated against the following configured space setpoint limits:
• Heating setpoint high limit;
• Heating setpoint low limit;
• Cooling setpoint high limit;
• Cooling setpoint low limit.