Application

Sequence of Operation
Control Temperature Setpoints
6
Siemens Industry, Inc. Application Note, App 2051 140-1137
2014-05-01
Sequence of Operation
The following paragraphs present the sequence of operation for the Siemens TEC Unit
Conditioner (Fan Coil) Controller.
Control Temperature Setpoints
This application has a number of different room temperature setpoints (DAY HTG
STPT, NGT CLG STPT, RM STPT DIAL, etc.). 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.
The setpoint deadband exists to allow the controller to provide a separation of the
heating and cooling temperature setpoints when a setpoint dial is enabled.
The setpoint deadband is the difference between the cooling and heating day setpoints
(DAY CLG STPT - DAY HTG STPT). The setpoint deadband can be disabled by
setting DAY HTG STPT equal to DAY CLG STPT. When DAY HTG STPT does not
equal DAY CLG STPT, a setpoint deadband (or zero energy band) is used.
The following values are used in the calculation of CTL STPT:
l Dial value is the value of RM STPT DIAL limited between the value of RM STPT
MIN and RM STPT MAX.
l Deadband is the value of the difference between DAY CLG STPT and DAY HTG
STPT, half of which is applied to establish the current heating and cooling
setpoints.
– Deadband = (DAY CLG STPT – DAY HTG STPT)