BACnet Objects

What a BACnet Object Is

BACnet represents application data as typed objects with defined properties, behaviors, and identifiers. That object model is a major reason BACnet integrations are more expressive than register-only protocols such as Modbus. Every object is identified by an Object Identifier that combines type and instance, such as analog-input:1 or binary-output:12, and the object types are defined in Clause 12 of ANSI/ASHRAE 135-2024.

The pages below index every standardized object type by family. Each one covers what the object models, where you meet it in the field, and its required and optional properties with datatypes.

Analog, Binary, and Multi-state

The core point objects on almost every job.

Object	Role
Analog Input	A measured analog value from a physical input
Analog Output	A commanded analog value driven to hardware
Analog Value	A software analog value (setpoint, calculated)
Binary Input	A two-state input (contact, status)
Binary Output	A commanded two-state output (relay, stage)
Binary Value	A software two-state value (mode, enable)
Multi-state Input	An input with several named states
Multi-state Output	A commanded multi-state output
Multi-state Value	A software multi-state value

Other Value Objects

Typed software values for integers, text, times, and dates.

Object	Role
Integer Value	A signed integer value
Positive Integer Value	An unsigned integer value
Large Analog Value	A double-precision analog value
CharacterString Value	A text-string value
OctetString Value	A raw byte-string value
BitString Value	A bit-string value
Date Value	A calendar-date value
Time Value	A time-of-day value
DateTime Value	A combined date-and-time value
Date Pattern Value	A date with wildcard fields for matching
Time Pattern Value	A time with wildcard fields for matching
DateTime Pattern Value	A date-and-time with wildcard fields

Device and Network

The objects that describe the device itself and its interfaces.

Object	Role
Device	The device’s identity, capabilities, and network parameters
Network Port	One network interface (IP, IPv6, MS/TP, SC) and its settings
File	A byte- or record-accessed file, used for backup and firmware

Scheduling

Object	Role
Schedule	Writes values on a weekly and exception schedule
Calendar	A list of dates and date ranges a Schedule references

Alarming and Events

Object	Role
Notification Class	Recipient lists and priorities for event notifications
Notification Forwarder	Re-distributes event notifications to other recipients
Alert Enrollment	Originates alerts as an event source
Event Enrollment	Attaches an event or fault algorithm to a referenced property
Event Log	Records the event notifications a device sees

Trending and Audit

Object	Role
Trend Log	Logs one property over time into a buffer
Trend Log Multiple	Logs several properties in lockstep
Audit Log	Records auditable operations
Audit Reporter	Originates audit notifications

Control

Object	Role
Loop	A PID control loop
Command	Runs a list of writes as a coordinated action
Staging	Sequences staged outputs from one value
Load Control	Sheddable-load management for demand response

Grouping and Structure

Object	Role
Group	Reads several objects’ properties in one request
Global Group	A group spanning objects across devices
Structured View	Organizes objects into a hierarchy

Metering and Calculation

Object	Role
Accumulator	A counting register for pulse metering
Pulse Converter	Scales accumulator pulses to engineering units
Averaging	Tracks minimum, maximum, and average of a value
Timer	A countdown or elapsed timer

Life Safety

Object	Role
Life Safety Point	A single life-safety point (detector, module)
Life Safety Zone	A group of life-safety points as one zone

Access Control

Object	Role
Access Door	A controlled door
Access Point	A point where access is granted or denied
Access Zone	An area with tracked occupancy
Access User	A person or entity with access rights
Access Rights	The rights that grant access
Access Credential	A credential assigned to a user
Credential Data Input	A reader’s captured authentication factor

Lighting

Object	Role
Lighting Output	A dimmable lighting output with fade and ramp
Binary Lighting Output	A switched lighting output
Channel	Fans a WriteGroup value out to member objects
Color	A commandable lighting color
Color Temperature	A commandable lighting color temperature

Elevators

Object	Role
Lift	An elevator car
Escalator	An escalator or moving walk
Elevator Group	A coordinated group of lifts

Key Properties

Property	Why It Matters
Object Identifier	Defines the object’s type and instance
Object Name	Human-readable label seen in tools and BMS front ends
Present Value	The current value of the point
Status Flags	Shows alarm, fault, override, and out-of-service state
Units	Adds engineering meaning to analog values
Description	Useful for commissioning and handoff clarity

Why Object Modeling Matters

BACnet projects often fail because the transport is healthy while the object model is wrong. A BMS may expect a writable Analog Output and receive a read-only Analog Input. A schedule may need a Schedule object, not just another analog setpoint. A trend consumer may need the history support a Trend Log provides that the exposed object set does not.

In practice, interoperability depends on choosing the right object type, assigning sensible names and instances, and confirming the expected properties and services are actually supported.

Related Pages

• BACnet
• BACnet Device Profiles
• BACnet Services
• BACnet Device Instance
• BACnet Object Types & Properties Reference