What the Elevator Group Object Is
The Elevator Group object, defined in Clause 12.58 of ANSI/ASHRAE 135-2024, is how a BACnet device represents a group of lifts or escalators controlled by a single supervisory controller. It is the parent that ties individual Lift and Escalator objects together, referencing them through Group_Members and identifying the machine room through Machine_Room_ID.
The Elevator Group also carries the group’s landing-call state. Landing_Calls reports the calls currently registered at each landing, and Landing_Call_Control can be written to register a landing call for the group to dispatch a car. This object has no Status_Flags, Event_State, or intrinsic-reporting properties: it is a structural and dispatch object rather than a monitored point.
Where You’ll See It
- Bank supervision. A group controller managing a bank of elevators exposes one Elevator Group object referencing every car in the bank.
- Landing-call dispatch. A lobby destination-dispatch panel registers a landing call through
Landing_Call_Control, and the group assigns a car. - Building models. An Elevator Group is commonly referenced from a Structured View that organizes a building’s lifts and escalators by machine room.
Required Properties
Clause 12.58 requires every Elevator Group object to provide these properties. Datatypes are the spec’s names: Unsigned is an integer, and the BACnet-prefixed types are structured values defined by the standard.
| Property | Datatype | What it holds |
|---|---|---|
Object_Identifier | BACnetObjectIdentifier | The object’s type and instance number, unique within the device |
Object_Name | CharacterString | The human-readable point name, unique within the device |
Object_Type | BACnetObjectType | Always elevator-group for this object |
Machine_Room_ID | BACnetObjectIdentifier | The machine room that houses this group |
Group_ID | Unsigned | The group’s identifier within the installation |
Group_Members | BACnetARRAY[N] of BACnetObjectIdentifier | The Lift and Escalator objects that make up this group |
Property_List | BACnetARRAY[N] of BACnetPropertyIdentifier | The list of properties this instance actually implements |
Optional Properties
The properties integrators meet most are Group_Mode, Landing_Calls, and Landing_Call_Control, which report and drive the group’s dispatch. This object has no intrinsic-reporting group. Audit_Level and Auditable_Operations are the audit-logging controls added in 135-2024.
| Property | Datatype | Group |
|---|---|---|
Description | CharacterString | General |
Group_Mode | BACnetLiftGroupMode | Elevator |
Landing_Calls | BACnetLIST of BACnetLandingCallStatus | Elevator |
Landing_Call_Control | BACnetLandingCallStatus | Elevator |
Audit_Level | BACnetAuditLevel | Auditing |
Auditable_Operations | BACnetAuditOperationFlags | Auditing |
Tags | BACnetARRAY[N] of BACnetNameValue | Tagging and profile |
Profile_Location | CharacterString | Tagging and profile |
Profile_Name | CharacterString | Tagging and profile |
Related Objects
- Lift: the elevator-car members of this group.
- Escalator: the escalator and moving-walk members of this group.
What Chipkin Provides
The Elevator Group object, including its group membership and landing-call dispatch model, is a first-class object type in the CAS BACnet Stack. Talk to us about modeling your device’s points.