User Manual

Sequence of Operation
Effective Room Temperature
11
Siemens Industry, Inc.
Application Note, App 14900
140-1231
2020-02-11
NOTE:
Effective Setpoint does not exist as a BACnet object. The controller determines what
the Effective setpoint is by evaluating the value of ModeEff.
If ModeEff is Heating, EffectiveSetpoint is the value of HeatingSp.
If ModeEff is Cooling, EffectiveSetpoint is the value of CoolingSp.
The actual value used by HeatingSp or CoolingSp at any given time is determined by
a number of factors. When operating without any external inputs, the thermostat’s
schedule will determine the effective operating mode, RM OP MODE.
If RM OP MODE is set to Comfort, then HeatingSp controls ComfortHtgSP and the
CoolingSp controls ComfortClgSP. If RM OP MODE is set to Economy, then
HeatingSp controls EconHtgSP and the CoolingSp controls EconClgSP. If RM OP
MODE is set to Protection, then HeatingSp controls ProtHtgSP and the CoolingSp
controls ProtClgSP.
NOTE:
You can override the effective setpoint through the local touchscreen interface or
remotely through the BACnet network by commanding Multistate Value 24,
SchedMode. The local override is only effective for the period determined by
HrsOvrRide (default value is 2 hours).
Effective Room Temperature
IndoorTmpEff:
When an external temperature sensor is not installed, IndoorTmpEff is the onboard
temperature measuring value.
When an external temperature sensor is installed, IndoorTmpEff can be configured to
either use an external measuring value or the average of external and onboard
measuring values.
The external temperature sensor can also be a network sensor. In this case, the
external temperature sensor does not have to be physically installed.
The RDY2000BN supports controlling to sensor input over the network. For example,
you can take one of the universal inputs, characterize it as a voltage input, remove it
from service, and expose it to the network as writeable. Then, you can assign the value
of another sensor over the network to this input.
If IndoorTmpEff does not read correctly, you can raise or lower it by changing the
value of TmpOffset to the appropriate positive or negative value to make
IndoorTmpEff read the correct value.
If the external temperature sensor fails, the unit can be manually switched to only use
an onboard sensor.
If the onboard sensor fails, the unit stops running.
Heating/Cooling Switchover
Auto Switchover enables the controller to automatically switch HVAC modes.
If IndoorTempEff > CoolingSp and Heating has turned off and has been off for the
length of time set in ChgOvrDly, the controller switches to Cooling mode.
If IndoorTempEff < HeatingSp and Cooling has turned off and has been off for the
length of time set in ChgOvrDly, the controller switches to Heating mode.