Application

Sequence of Operation
Control Temperature Setpoints
7
Siemens Industry, Inc.
Application Note, App 6663
140-1109
2014-10-27
Sequence of Operation
The following paragraphs present the sequence of operation for Application 6663 --
Constant Volume with Hot Water Reheat.
NOTE:
This application will not automatically switch between heating and cooling. If a
seasonal switchover (for example, summer to winter) is to occur, PPCL in the
controller or in the field panel must command HEAT.COOL. This allows the controller
to use the appropriate setpoints for the season.
Control Temperature Setpoints
CTL STPT is Overridden:
If CTL STPT is overridden, that value is used regardless of any other settings. This
disables the setpoint deadband feature.
CTL STPT in Night Mode:
The controller is in Night Mode if DAY.NGT = NGT and NGT OVRD = NGT.
When the controller is in night mode, CTL STPT holds the value of NGT CLG STPT or
NGT HTG STPT depending on the value of HEAT.COOL. When the controller is in
night mode, the value of RM STPT DIAL is ignored.
CTL STPT in Day Mode:
The controller is in Day Mode if DAY.NGT = DAY or NGT OVRD = DAY.
Without setpoint dial:
When the controller is in day mode and STPT DIAL = NO, CTL STPT holds the value
of DAY CLG STPT or DAY HTG STPT depending on the value of HEAT.COOL.
With setpoint dial:
When the controller is in day mode and STPT DIAL = YES, CTL STPT holds a value
based on RM STPT DIAL depending on your room unit model/revision.
The following sections describe the value of CTL STPT based on room unit type and
configuration:
 CTL STPT using Standard/Absolute Mode (Digital Room Unit, Revision 26 and
later)
 CTL STPT using Warmer/Cooler Mode (Digital Room Unit, Revision 26 and later)
 CTL STPT using Standard/Absolute Mode (Analog or Digital Room Unit)
 CTL STPT using Warmer/Cooler Mode (Analog Room Unit Only)
NOTE:
If RM STPT DIAL is failed, it maintains the last known value.