Cooling Operation - Trane Tracer VV550 Installation, Operation And Maintenance Manual

Table 29.Heating and cooling changeover logic (continued)
System
command,
communicated Primary air
application temp,
mode, communicated
communicated source temp or
heat/cool mode local input
a. The active heat/cool mode matches the system command if the command is anything other than auto.
b. If the system command is auto, the active heat/cool mode matches the zone demand.
c. If the system command is anything other than auto, zone demand is not considered.
d. If the system command is heat or cool and the primary air temperature is invalid, the primary air temperature is assumed to
match the system mode. This will result in problem operation.
e. Based on the configured default primary air temperature (heating or cooling). An assumption is made about the primary air
temperature. This will result in problem operation.
f. If the space temperature < heat setpoint, then zone demand is heat and reported heat/cool mode is heat. If the space
temperature > cool setpoint and space temperature > heat setpoint + 0.5°F (0.28°C), then zone demand is cool and reported
heat/cool mode is cool.
g. If primary air temperature > configured reheat enable setpoint, then primary air temperature is hot. (Primary air is hot enough
for heating and too hot for reheat) If primary air temperature > configured auto changeover setpoint, then primary air
temperature is warm (hot in table above). (Primary air is hot enough for heating and reheat can be used.) If primary air
temperature < configured auto changeover setpoint – 10°F (5.56°C), then primary air temperature is cold. (Primary air is cold
enough for cooling and reheat can be used.) No change in hysteresis region.
h. Refer to Table 40 on p.
General Notes:
• Controller state is based on either system command (if heat or cool) or primary air temperature.
• Valve action is based on primary air temperature or configured default primary air temperature.
• Active minimum is based on valve action.

Cooling Operation

Under space temperature control during the cooling mode (communicated heat/cool
mode is cool), the controller attempts to maintain the active space temperature at the
active space cooling setpoint. Based on the controller occupancy mode, the active space
cooling setpoint is either the occupied cooling setpoint, the occupied standby cooling
setpoint, or the unoccupied cooling setpoint.
The outputs are controlled based on the unit configuration and the required cooling
capacity. At 0% required cooling capacity, the air valve is closed or at the active minimum
flow setpoint. As the required cooling capacity increases, the air valve opens above the
minimum position. At 100% required cooling capacity, the air valve opens to the
maximum position or to the active maximum flow setpoint.
All units have a modulating air valve. The modulating air valve is used to control the
volume of air flowing through the diffusers and into the space. Modulating the volume
of air modulates the unit cooling capacity.
Also, units may have local or remote reheat. The reheat may be hydronic or electric.
Reheat is allowed to turn On when the space temperature is below the heating setpoint.
Refer to
CNT-SVX17G-EN
Local
zone
g f
demand
Cool
60.
"Reheat Control" on page
Reported
heat/
cool
mode or
reported
unit Air
status valve Air valve
a, b c
mode action position
Cool Heat/ Note e
Cool
e
45.
Sequence of Operations
Active
h
minimum
Note e
43