Heating/cooling state determination (HCStaDtr11)
Overview
The application function "Heating/cooling state determination 11" (HCStaDtr11) determines whether HVAC control is currently heating or cooling or neither, and supplies this information in a BACnet object.
In addition it ensures a minimum switching delay (changeover delay) between heating and cooling.
Function
Input:
The AF compares the room temperature to current setpoints, and checks whether a PID controller actively controls a device.
Output:
The heating/cooling state (HCSta) is supplied for use by the following AFs: RThLd11, ROpUn11 (as a BACnet object) and for SpTR11 (as an internal connection). In addition it provides a release heating and a release cooling signal (as an internal connection) to enable the heating and cooling room temperature control sequences.
Configuration:
The switching points can be shifted and a time delay can be configured to smooth switching.
Configuration
Objects
Description | Object | Default value |
|---|---|---|
Shift of switch-on point for cooling state | ShftOnPtCSta | 0 [K] |
Shift of switch-on point for heating state | ShftOnPtHSta | 0 [K] |
Switch-on delay for heating/cooling changeover | DlyOnHCChovr | 2 [min] |
Temperature difference unit | TDiffUnit | [K] |
Interface
Interface | Description | Type | Ref. | Owned by |
|---|---|---|---|---|
HCSta | Heating/cooling state 1:Neither | MCalcVal | ● | - |
Engineering and commissioning
The Switch-on delay for heating/cooling changeover (DlyOnHCChovr) must be configured in other places as well:
- In this AF
- In all 4-pipe AFs present in the plant. This prevents equipment damage to the central heating and cooling systems that supply the heated/chilled coil or ceiling
In the event of differing values the higher value wins.