Application

Sequence of Operation
Control Temperature Setpoints
6
Siemens Industry, Inc. Application Note, App 2033 140-1023
2015-08-07
Sequence of Operation
The following paragraphs present the sequence of operation for Application 2033 --
Hot Water Reheat.
Control Temperature Setpoints
Depending on the controller’s current operational mode (occupied or unoccupied), CTL
STPT holds the value of one of the following setpoints.
NOTE:
This application does not automatically switch between heating and cooling. If a
seasonal switchover (for example, summer to winter) should occur, the field panel
must command HEAT.COOL. This allows the controller to use the appropriate
setpoints for the season.
Occupied Mode – CTL STPT holds the value of OCC CLG STPT in cooling mode and
OCC HTG STPT in heating mode. If the room temperature sensor has a setpoint dial
and STPT DIAL = YES, CTL STPT holds the value of RM STPT DIAL.
If the setpoint dial is used and RM STPT DIAL < RM STPT MIN, CTL STPT holds the
value of RM STPT MIN. If RM STPT DIAL > RM STPT MAX, CTL STPT holds the
value of RM STPT MAX.
Unoccupied Mode – CTL STPT holds the value of UOC CLG STPT in cooling mode
and UOC HTG STPT in heating mode. The setpoint dial is not used in unoccupied
mode.
This application has a number of different room temperature setpoints (DAY HTG
STPT, NGT CLG STPT, RM STPT DIAL, and so on.). The application actually controls
using the CTL STPT. CTL STPT is set to different values depending on its override
status, the time of day, whether or not a temperature deadband (zero energy band)
has been configured, and the type of RTS used.
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 is set based on
the value of the setpoint dial and the setpoint deadband.