Supply chain changeover condition for air (SplyChovrAir11)
Overview
The application function "Supply chain changeover condition for air 11" (SplyChovrAir11) evaluates the heating/cooling demand from the rooms and decides whether the central air can be used for heating or for cooling.
Function
The decision whether the air should be used for heating or cooling is based on the heating/cooling demand from the segments. The heating/cooling demand is assessed and an evaluated changeover condition is distributed via SplyAir-Grouping to the room segment(s), indicating the heating/cooling changeover condition of the supply air.
ChoAirModCmd - ChoAirModCmd is the enumerated mode command for the air changeover condition. If it is set to Heating, the setpoint for the AHU supply temperature is shifted up; if set to Cooling, the setpoint is shifted down. See SplySpTSu11 for additional information. (During heating, the cooling controllers are disabled; during cooling, the heating controllers are disabled.)
Additional enumerations for ChoAirModCmd: Neutral (heating and cooling controllers both enabled); Neither (heating and cooling controllers both disabled).
Note
ChoAirModCmd can be overridden via BACnet with a higher priority – see Engineering and commissioning for when this should be done.
Changeover determination logic – The system evaluates the number of segments requesting heat (ChoAirNumHDmd) and the number of segments requesting cooling (ChoAirNumCDmd). The SplyAir-Grouping tag "HCDmd" reads the results, and the side with most heating or cooling requests wins.
Example:
50 segments require cooling, 30 segments require heating;
The evaluation = Cooling. The result will be distributed by the SplyAir-Grouping tag "ChovrCndAir" to enable or disable the room controllers.
Configuration
None
Interface
Interface | Description | Type | Ref. | Owned by |
|---|---|---|---|---|
ChoAirModCmd | Command for changeover mode air 1:Neither | MPrcVal | ● | - |
ChoAirNumCDmd | Changeover function for supply chain air number of cooling demand | ACalcVal | ● | - |
ChoAirNumHDmd | Changeover function for supply chain air number of heating demand | ACalcVal | ● | - |
SplyAirMst | Manager for supply chain air | GrpMaster | ◉ | SplyAir11 |
Engineering and commissioning
ChoAirModCmd
For central air handlers that have no changeover function, ChoAirModCmd must be overridden and set to the state that matches air handler operation (typically Cooling). For air handlers with a changeover function, ChoAirNumHDmd and ChoAirNumCDmd can be fed / sent to an outside function to determine changeover condition, with the resulting output used to override ChoAirModCmd.