What the Lift Object Is
The Lift object, defined in Clause 12.59 of ANSI/ASHRAE 135-2024, is how a BACnet device represents a single elevator car: its position, direction of travel, door states, operating mode, load, and faults. A car can have more than one door, so the door-related properties are arrays whose matching indices refer to the same car door and its corresponding landing door.
The Lift object exposes the externally visible condition of the car to a building management system without controlling the elevator’s internal logic. It belongs to an Elevator Group identified through Elevator_Group, Group_ID, and Installation_ID. Lift objects that support intrinsic reporting apply the CHANGE_OF_STATE event algorithm on the Passenger_Alarm property, alarming when a passenger alarm becomes active, and deliver it through the event notification services.
Where You’ll See It
- Elevator monitoring. A supervisory controller carrying the B-EC Elevator Controller profile exposes each car as a Lift object so a BMS can display position, direction, and door status.
- Fault and alarm reporting.
Fault_Signalslists active lift faults andPassenger_Alarmraises the in-car alarm to the building’s alarm system. - Energy tracking. With
Energy_MeterandEnergy_Meter_Ref, the car’s drive energy can be trended alongside other building loads.
Required Properties
Clause 12.59 requires every Lift object to provide these properties. Datatypes are the spec’s names: Unsigned is an integer, BOOLEAN a true/false flag, 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 lift for this object |
Status_Flags | BACnetStatusFlags | Four health flags: in-alarm, fault, overridden, out-of-service |
Elevator_Group | BACnetObjectIdentifier | The Elevator Group object this car belongs to |
Group_ID | Unsigned | The car’s group identifier within the elevator installation |
Installation_ID | Unsigned | The identifier of the elevator installation |
Car_Position | Unsigned | The floor the car is currently at |
Car_Moving_Direction | BACnetLiftCarDirection | Which way the car is moving (up, down, stopped) |
Car_Door_Status | BACnetARRAY[N] of BACnetDoorStatus | The status of each car door |
Passenger_Alarm | BOOLEAN | Whether the in-car passenger alarm is active |
Out_Of_Service | BOOLEAN | When true, the object’s values are decoupled from the physical lift |
Fault_Signals | BACnetLIST of BACnetLiftFault | The lift faults currently active |
Property_List | BACnetARRAY[N] of BACnetPropertyIdentifier | The list of properties this instance actually implements |
Optional Properties
The properties integrators meet most are the elevator group (Car_Mode, Car_Load, Next_Stopping_Floor, Registered_Car_Call, Landing_Door_Status) that describe what the car is doing, and the energy fields. The intrinsic-reporting group generally appears or is absent as a set. Audit_Level and Auditable_Operations are the audit-logging controls added in 135-2024.
| Property | Datatype | Group |
|---|---|---|
Description | CharacterString | General |
Floor_Text | BACnetARRAY[N] of CharacterString | Elevator |
Car_Door_Text | BACnetARRAY[N] of CharacterString | Elevator |
Assigned_Landing_Calls | BACnetARRAY[N] of BACnetAssignedLandingCalls | Elevator |
Making_Car_Call | BACnetARRAY[N] of Unsigned | Elevator |
Registered_Car_Call | BACnetARRAY[N] of BACnetLiftCarCallList | Elevator |
Car_Assigned_Direction | BACnetLiftCarDirection | Elevator |
Car_Door_Command | BACnetARRAY[N] of BACnetLiftCarDoorCommand | Elevator |
Car_Door_Zone | BOOLEAN | Elevator |
Car_Mode | BACnetLiftCarMode | Elevator |
Car_Load | REAL | Elevator |
Car_Load_Units | BACnetEngineeringUnits | Elevator |
Next_Stopping_Floor | Unsigned | Elevator |
Car_Drive_Status | BACnetLiftCarDriveStatus | Elevator |
Landing_Door_Status | BACnetARRAY[N] of BACnetLandingDoorStatus | Elevator |
Higher_Deck | BACnetObjectIdentifier | Elevator |
Lower_Deck | BACnetObjectIdentifier | Elevator |
Energy_Meter | REAL | Elevator |
Energy_Meter_Ref | BACnetDeviceObjectReference | Elevator |
Reliability | BACnetReliability | Fault detection |
Time_Delay | Unsigned | Intrinsic reporting |
Time_Delay_Normal | Unsigned | Intrinsic reporting |
Event_Detection_Enable | BOOLEAN | Intrinsic reporting |
Notification_Class | Unsigned | Intrinsic reporting |
Event_Enable | BACnetEventTransitionBits | Intrinsic reporting |
Event_State | BACnetEventState | Intrinsic reporting |
Acked_Transitions | BACnetEventTransitionBits | Intrinsic reporting |
Notify_Type | BACnetNotifyType | Intrinsic reporting |
Event_Time_Stamps | BACnetARRAY[3] of BACnetTimeStamp | Intrinsic reporting |
Event_Message_Texts | BACnetARRAY[3] of CharacterString | Intrinsic reporting |
Event_Message_Texts_Config | BACnetARRAY[3] of CharacterString | Intrinsic reporting |
Event_Algorithm_Inhibit_Ref | BACnetObjectPropertyReference | Intrinsic reporting |
Event_Algorithm_Inhibit | BOOLEAN | Intrinsic reporting |
Reliability_Evaluation_Inhibit | BOOLEAN | Fault detection |
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
- Escalator: the sibling object for escalators and moving walks in the same elevator group.
- Elevator Group: the supervisory object that groups the cars and escalators controlled together.
What Chipkin Provides
The Lift object, including its car-door arrays, fault signals, and CHANGE_OF_STATE passenger-alarm reporting, is a first-class object type in the CAS BACnet Stack. Talk to us about modeling your device’s points.