Application

Sequence of Operation
Room Temperature and Setpoint
17
Siemens Industry, Inc.
Application Note, App 2927
140-1311
2015-07-07
Room Temperature and Setpoint
The application uses the CTL STPT as the setpoint for the Room Temperature PID
Loop. When CTL STPT is not overridden and not being controlled by a field panel, then
ROOM STPT and CTL STPT are related to each other as follows:
 If ROOM STPT is greater than RM STPT MAX, then CTL STPT is set equal to RM
STPT MAX.
 If ROOM STPT is less than RM STPT MIN, then CTL STPT is set equal to RM
STPT MIN.
 If ROOM STPT is less than or equal to RM STPT MAX and greater than or equal to
RM STPT MIN, then CTL STPT is set equal to ROOM STPT.
If CTL STPT is overridden or being controlled by a field panel, then RM STPT MIN
and/or RM STPT MAX have no effect on CTL STPT.
The application also uses CTL TEMP as the temperature input for the Room
Temperature PID Loop. When CTL TEMP is not overridden, then:
CTL TEMP = ROOM TEMP + TEMP OFFSET.
Room Temperature Offset
NOTE:
The Room Temperature Offset feature is optional.
TEMP OFFSET is a user-adjustable offset that will compensate for deviations between
the value of ROOM TEMP and the actual room temperature. This corrected value is
displayed in CTL TEMP.
CTL TEMP = ROOM TEMP + TEMP OFFSET
Example
If the actual room temperature is 72.0°F, and the value of ROOM TEMP is 73.0°F, then
the value entered into TEMP OFFSET is
-1.0. In this case, the value of ROOM TEMP
would read 73.0°F, but the value of CTL TEMP would read 72.0°F.
Room Unit Identification
 For Analog Room Units (Series 1000) – The revision number is visually identified
by its case.
 For Digital Room Units (Series 200/2300 Firmware Revision 25 or earlier) – The
revision number displays for 5 seconds when the room unit is first powered up.
These room units will display laptop when a laptop is connected and will no
longer update room temperature sensor values.
 For Digital Room Units (Series 2200/2300 Firmware Revision 26 and later) – The
revision number displays for 5 seconds when the room unit is first powered up or
when a laptop is disconnected. These room units will continue to display and
update the room temperature sensor values when a laptop is connected.