Operating Instructions
Table Of Contents
- Table of Contents
- How To Use This Manual
- Chapter 1—Hardware
- Chapter 2—Applications for ATEC— Base VAV
- Chapter 3—Applications for ATEC—VAV with Reheat
- Chapter Overview
- Introduction
- Application 2500: VAV Cooling Only
- Application 2501: VAV Cooling or Heating
- Application 2522: VAV with Electric Reheat or Baseboard Radiation
- Application 2523: VAV with Hot Water Reheat (only one reheat valve)
- Application 2524: VAV Series Fan Powered with One Stage of Electric Reheat
- Application 2526: VAV Parallel Fan Powered with One Stage of Electric Reheat
- Application 2473: Slave Mode
- Chapter 4—Point Database
- Chapter 5—Troubleshooting
- Glossary
- Index
Chapter 3—Applications for ATEC—VAV with Reheat
3-70 Siemens Building Technologies, Inc.
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.
Day and Night Modes
The day/night status of the space is determined by the status of DAY.NGT (Point 29). The
control of this point differs depending on whether the controller is monitoring the status of a
wall switch or is connected to a field panel.
When a wall switch is physically connected to the controller at the AI/DI port labeled “AI 4”
(Figure 3-20 on page 3-67 and Figure 3-23 on page 3-76), and WALL SWITCH (Point 18) is
set to YES, the controller monitors the status of DI 4 (Point 24). When DI 4 is ON (the switch
is closed), DAY.NGT is set to DAY indicating that the controller is in day mode. When DI 4 is
OFF (the switch is open), DAY.NGT is set to NIGHT indicating that the controller is in night
mode.
When WALL SWITCH is set to NO, the controller does not monitor the status of the wall
switch, even if one is connected to it. In this case, 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 the Powers Process Control Language (PPCL) User’s
Manual (125-1896) and Field Panel User’s Manual (125-1895) for more information.