Automatic Heat/Cool Mode Determination; Sequence Of Operation - Trane ZN. LonWorks control Manual

Figure 1
Unoccupied
heating stp
CNT-SVX13B-E4
Features
Occupied
heating stp
Occupied
standby
heating stp
Local setpoint
Typically, the range of the local
setpoint is from 10°C to 29°C. The
effective setpoint can be limited in
cooling and heating mode via
configuration parameters (see
default values).
Automatic Heat/cool mode
determination
The controller automatically
determines whether heating or
cooling is needed based on space
and system conditions. Utilizing a
cascade proportional/integral (PI)
control algorithm to maintain the
space temperature at the active
heating or cooling setpoint. The
controller measures the space
temperature and reads the
temperature setpoint to determine
the required unit's heating or cooling
capacity (0-100%) and drive the fan
speed (if 'auto') and the valve
position accordingly.
Occupied
cooling stp
Occupied
Dead standby
zone cooling stp
Unoccupied
cooling stp

Sequence of operation

Off: Fan is off, valves are closed.
Auto: Fan speed control in the auto
setting allows the modulating control
valve option and three-speed fan to
work cooperatively to meet precise
capacity requirements, while
minimizing fan speed (motor
energy/acoustics) and valve position
(pump energy/chilled water reset). As
the capacity requirement increases
at low fan speed, the water valve
opens. When the low fan speed
capacity switch point is reached
(water valve fully open), the fan
automatically switches to medium
speed and the water valve
repositions to maintain an equivalent
capacity. The reverse sequence takes
place with a decrease in required
capacity (see figures 2 and 3).
Low, Medium, High:The fan will run
continuously at the selected speed
and the valve will cycle to meet the
setpoint.
7