Operating Instructions

Application 2520: VAV Cooling Only
Siemens Building Technologies, Inc. 2-5
Ordering Notes
Actuating Terminal Equipment Controller—Electronic Output
Single unit 550-400
10-pack 550-400P10
Contact your local Siemens Building Technologies representative for additional product
numbers.
Temperature sensor (select one)
• Terminal Equipment Controller room temperature sensor
• Duct temperature sensor, 10K
Ω , TEC (return-duct sensor)
4-inch (10.2 cm) 540-128
18-inch (46 cm) 540-739
Sequence of Operation
Control Temperature Setpoints
Depending on the controller’s current operational mode (day or night), CTL STPT (Point 92)
holds the value of one of the following setpoints:
Day Mode—CTL STPT holds the value of DAY CLG STPT (Point 6). If the room temperature
sensor has a setpoint dial and STPT DIAL (Point 14) is set to YES, CTL STPT holds the
value of RM STPT DIAL (Point 13).
If the setpoint dial is used and the value of RM STPT DIAL is less than the value of RM STPT
MIN (Point 11), CTL STPT holds the value of RM STPT MIN. If the value of RM STPT DIAL is
greater than the value of RM STPT MAX (Point 12), CTL STPT holds the value of RM STPT
MAX.
Night Mode—CTL STPT holds the value of NGT CLG STPT (Point 8).
NOTE: The value of CTL TEMP (Point 78) is the same as ROOM TEMP (Point 4), unless
CTL TEMP is overridden.
Day and Night Modes
The day/night status of the space is determined by the status of DAY.NGT (Point 29).
If the controller is operating stand-alone,, it stays in day mode all the time. If the controller is
operating with centralized control (that is, connected to a field panel), the field panel, can
send an operator or PPCL command to override the status of DAY.NGT. See APOGEE
®
PPCL User’s Manual (125-1896) and Field Panel User’s Manual (125-1895) for more
information.