Commissioning Instructions

Central Functions

Central Functions Basics

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5 Central Functions

5.1 Central Functions Basics

The Central Function Application or Coordinator is implemented through the use of a DXR2E/M.18

controller. Central Functions coordinate the actions of the room controller to the primary plant. A DXR

running the Central Function Application facilitates group data exchange between room applications or

DXRs and the primary plant controller or Field Panel. It does this by using group member and group master

objects to communicate with RA Applications and by using ordinary BACnet objects to communicate with

the primary application. This avoids the need to field-configure BACnet object references in the Field

Panel.

Central Functions and Group Data Exchange are not mandatory because the controllers support the

read/write of standard BACnet Objects as we currently use them.

One Central Function DXR can collect up to 250 Group Member objects. It can read and write to those

objects, as well as read and write using BACnet objects from the Field Panel.

More than one group may be required depending on the size of the application, as only one central function

DXR should be used per AHU.

If there is more than one group, the group number can be changed in ABT Site under the Central Functions

task. The first group will have a default Group Number of 1, and subsequent Group Numbers can be

changed as necessary. See Configuring Group Members and Masters [➙ Error! Bookmark not defined.]

for a detailed look at Group Member assignment.

There are multiple applications for Central Functions that can be used in a variety of ways including:

● Start/Stop coordination

● Minimizing Duct Pressure

● Optimizing Supply Air Temperature

● Controlling Scheduling Modes (Warm-up, Cool Down, etc.)

● Optimizing Hot and/or Chilled Water parameters (Supply Temperature, Start/Stop modes)

Central Functions can also be bundled together to collect and distribute Group Member data to / from

multiple other Central Function DXRs. All central functions have “bundled” variants that are used as

subordinate central functions to one master. If one central function is not be enough to control all of the

data from the room controllers, a higher-level Central Function DXR can be used to communicate between

the lower level central functions to the AHU/primary plant.

The following diagram shows the hierarchy of bundled functions, and how the Group members and Group

masters communicate with one another. The bundled Central Functions collect data from each floor, while

the corresponding Master Central Function collects the data from the subordinate bundled members. For

more information on bundling, see ABT Site Help.