Operating Instructions

Application 2501: VAV Cooling or Heating
Siemens Building Technologies, Inc. 3-15
Ordering Notes
Actuating Terminal Equipment Controller with Reheat—Electronic Output
Single unit 550-405
10-pack 550-405P10
Contact your local Siemens Building Technologies representative for additional product
numbers.
Autozero module (optional)
Duct temperature sensor, 100K
Ω (supply-duct sensor, optional)
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) or DAY HTG STPT
(Point 7). 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) or NGT HTG STPT
(Point 9).
NOTE: The value of CTL TEMP (Point 78) is the same as ROOM TEMP (Point 4), unless
CTL TEMP is overridden.