Tools · BACnet Object Reference

BACnet Object Reference BACnet

The numbers a controller, a packet capture, or a workstation hands you instead of names.

Object Types is the Object_Type enumeration — what kind of point an object is (type 1 = Analog Output). Property IDs is the Property_Identifier enumeration — which field of an object you are reading (property 85 = Present_Value), and the numbers are the same across every object type. Eng. Units is the field-common slice of the Units enumeration, grouped by domain. Type a name, a number, or a symbol to filter all three.

Filter by name or number

BACnet object types (Object_Type enumeration)

The Object_Type value carried in every object identifier. AI / AO / AV and BI / BO / BV are the day-to-day four-fifths of any device.

Type	Object	What it is
0	Analog Input (AI)	A sensed analog value coming in — temperature, pressure, humidity.
1	Analog Output (AO)	A commandable analog value going out — valve, damper, VFD speed.
2	Analog Value (AV)	An analog value living in software — a setpoint or calculated number.
3	Binary Input (BI)	A sensed two-state value coming in — a status or switch contact.
4	Binary Output (BO)	A commandable two-state output — a relay or start/stop command.
5	Binary Value (BV)	A two-state value living in software — a mode flag or enable.
6	Calendar	A list of dates and date ranges that schedules reference.
7	Command	Writes a set of values to many objects from one write.
8	Device	The controller itself — one per device, holding its identity and capabilities.
9	Event Enrollment	Defines an alarm/event condition and who gets notified.
10	File	A file reachable through BACnet file services.
11	Group	A read-back bundle of properties from other objects.
12	Loop	A built-in PID control loop.
13	Multi-state Input (MSI)	A sensed enumerated state coming in.
14	Multi-state Output (MSO)	A commandable enumerated state going out.
15	Notification Class	Routes event notifications to recipients with priorities.
16	Program	An executing control program inside the device.
17	Schedule	A weekly + exception schedule that writes a value on time.
18	Averaging	Records the min, max, and average of a sampled property.
19	Multi-state Value (MSV)	An enumerated state living in software.
20	Trend Log	Records samples of a property over time.
21	Life Safety Point	A fire / life-safety point.
22	Life Safety Zone	A fire / life-safety zone.
23	Accumulator	A pulse / meter accumulator — kWh, gallons, pulses.
24	Pulse Converter	Scales accumulator pulses into engineering units.
25	Event Log	Records event notifications over time.
26	Global Group	A read-back bundle spanning several devices.
27	Trend Log Multiple	Logs several properties on one shared timebase.
28	Load Control	Sheds electrical load on demand.
29	Structured View	A tree node for organizing objects — folders.
30	Access Door	A physical access-control door.
31	Timer	A countdown timer that changes state and can fire writes when it expires.
32	Access Credential	An access-control credential — the card or fob identity.
33	Access Point	An access-control decision point — a reader and the door it grants.
34	Access Rights	Which credentials pass which access points, and when.
35	Access User	The person (or role) a set of credentials belongs to.
36	Access Zone	An area bounded by access-controlled doors, with occupancy state.
37	Credential Data Input	Reads raw credential data from a reader — card number, PIN.
38	Network Security	Legacy network-security configuration (deprecated by later editions).
39	BitString Value	A bit-string value living in software.
40	CharacterString Value	A text-string value living in software.
41	DatePattern Value	A recurring date pattern — e.g. every second Tuesday.
42	Date Value	A single calendar-date value.
43	DateTimePattern Value	A recurring date-and-time pattern.
44	DateTime Value	A single date-and-time value.
45	Integer Value	A signed whole-number value living in software.
46	Large Analog Value	A double-precision analog value — numbers a 32-bit float would round.
47	OctetString Value	A raw byte-string value.
48	Positive Integer Value	An unsigned whole-number value living in software.
49	TimePattern Value	A recurring time-of-day pattern.
50	Time Value	A single time-of-day value.
51	Notification Forwarder	Re-routes event notifications onward to other recipients.
52	Alert Enrollment	Funnels a device's internal alerts into one notification point.
53	Channel	Fans one written value out to a group of property references.
54	Lighting Output	A dimmable lighting channel.
55	Binary Lighting Output	An on/off lighting channel.
56	Network Port	A network interface's configuration — IP, MS/TP, BACnet/SC.
57	Elevator Group	A bank of lifts or escalators monitored as one group.
58	Escalator	An escalator's status and faults.
59	Lift	An elevator car's status, position, and faults.
60	Staging	Maps an analog Present_Value onto on/off stages via configured thresholds — equipment staging.
61	Audit Log	Records who changed what — an audit trail of operations.
62	Audit Reporter	Generates the audit notifications an Audit Log records.
63	Color	A color command for color-capable lighting.
64	Color Temperature	A correlated-color-temperature command for tunable-white lighting.
No object types match that filter.

The full 0–64 range through ASHRAE 135-2020 and its addenda. Unassigned numbers below 128 are reserved to ASHRAE for future editions; 128–1023 are vendor-proprietary — whose extension it is, the device's vendor ID says. Decode a packed Object Identifier with the BACnet/IP Hex Converter's Object ID tab.

BACnet property identifiers (Property_Identifier enumeration)

The Property_Identifier numbers are constant across every object type — property 85 is Present_Value whether the object is an AI or a BO.

ID	Property	Meaning
4	Active_Text	The display text for a binary object's active state.
11	APDU_Timeout	Milliseconds the device waits for a reply before retrying.
17	Notification_Class	Which Notification Class object routes this object's events.
22	COV_Increment	The smallest change that triggers a Change-of-Value notification.
25	Deadband	How far back inside the limits a value must come before returning to normal.
28	Description	Free-text description of the object.
30	Device_Address_Binding	The device-instance → network-address bindings the device has learned.
31	Device_Type	Free text describing the attached hardware — e.g. the sensor type.
35	Event_Enable	Which transitions (to-offnormal / to-fault / to-normal) send notifications.
36	Event_State	normal / fault / offnormal / high-limit / low-limit.
38	Exception_Schedule	The Schedule object's override entries — holidays and one-offs.
40	Feedback_Value	The proven value an output compares against its command for feedback alarms.
44	Firmware_Revision	The device's firmware version string.
45	High_Limit	The high alarm limit for limit-enabled objects.
46	Inactive_Text	The display text for a binary object's inactive state.
52	Limit_Enable	Enables high-limit and low-limit alarming independently.
56	Local_Date	The device's current date.
57	Local_Time	The device's current time.
58	Location	Free text saying where the device is installed.
59	Low_Limit	The low alarm limit for limit-enabled objects.
62	Max_APDU_Length_Accepted	The largest message the device can receive.
63	Max_Info_Frames	MS/TP: how many messages a node may initiate per token hold.
64	Max_Master	MS/TP: the highest master address the token search will poll.
65	Max_Pres_Value	The highest Present_Value the object supports.
66	Minimum_Off_Time	Short-cycle protection — seconds an output must stay off.
67	Minimum_On_Time	Short-cycle protection — seconds an output must stay on.
69	Min_Pres_Value	The lowest Present_Value the object supports.
70	Model_Name	The device's model string.
72	Notify_Type	Whether the object issues alarms or events.
73	Number_Of_APDU_Retries	How many times the device re-sends an unanswered request.
74	Number_Of_States	How many states a multi-state object defines.
75	Object_Identifier	The object's type + instance number — e.g. analog-input, 4.
76	Object_List	The device's list of all its objects — read during discovery.
77	Object_Name	A text name, unique within the device.
79	Object_Type	The object's enumerated type — see the Object Types tab.
81	Out_Of_Service	True decouples Present_Value from the physical I/O for testing.
84	Polarity	normal / reverse for binary objects — physical vs. logical sense.
85	Present_Value	The live value — the property you read and write most.
87	Priority_Array	16 command slots; the lowest-numbered (highest-priority) non-null slot wins (commandable objects).
88	Priority_For_Writing	The command priority (1–16) a Schedule writes at.
97	Protocol_Services_Supported	The bitmap of BACnet services the device implements.
98	Protocol_Version	The BACnet protocol version — 1 on everything fielded.
103	Reliability	Why a value is untrustworthy — over-range, open-loop, no-fault.
104	Relinquish_Default	The value used when every priority slot is null.
107	Segmentation_Supported	Whether the device can segment long messages, and in which direction.
110	State_Text	The array of state names for a multi-state object.
111	Status_Flags	{ in-alarm, fault, overridden, out-of-service }.
112	System_Status	operational / download-in-progress / non-operational and friends.
113	Time_Delay	Seconds a condition must persist before the event transition fires.
117	Units	The engineering-units enumeration — see the Eng. Units tab.
120	Vendor_Identifier	The manufacturer's assigned BACnet vendor ID number.
121	Vendor_Name	The manufacturer's name.
123	Weekly_Schedule	The Schedule object's normal Monday-to-Sunday program.
139	Protocol_Revision	Which revision of ASHRAE 135 the device implements.
141	Record_Count	Trend Log: how many records the buffer holds right now.
145	Total_Record_Count	Trend Log: how many records have ever been collected.
152	Active_COV_Subscriptions	The COV subscriptions the device is currently serving.
155	Database_Revision	Bumps whenever the device's object database changes — a re-discovery cue.
371	Property_List	The list of properties an object actually has (newer-revision devices).
372	Serial_Number	The device's serial number (newer-revision devices).
No properties match that filter.

The field-relevant slice, in numeric order — the full enumeration runs past 500 and newer editions keep adding to it. The numbers above are the ones you meet reading, overriding, and commissioning points; 85, 87, and 104 are the daily three.

BACnet engineering units (Units enumeration)

The value of an object's Units property (117), grouped by domain. The full enumeration runs past 250 values; these are the ones building systems actually use.

Enum	Engineering unit	Domain
62	degrees-Celsius (°C)	Temperature
63	kelvin (K)	Temperature
64	degrees-Fahrenheit (°F)	Temperature
65	degree-days-Celsius	Temperature
66	degree-days-Fahrenheit	Temperature
120	delta-degrees-Fahrenheit (Δ°F)	Temperature
121	delta-kelvin (ΔK)	Temperature
23	joules-per-kilogram-dry-air (J/kg)	Humidity & enthalpy
24	btus-per-pound-dry-air (Btu/lb)	Humidity & enthalpy
28	grams-of-water-per-kilogram-dry-air (g/kg)	Humidity & enthalpy
29	percent-relative-humidity (%RH)	Humidity & enthalpy
53	pascals (Pa)	Pressure
54	kilopascals (kPa)	Pressure
55	bars (bar)	Pressure
56	pounds-force-per-square-inch (psi)	Pressure
58	inches-of-water (in. w.c.)	Pressure
59	millimeters-of-mercury (mmHg)	Pressure
61	inches-of-mercury (inHg)	Pressure
84	cubic-feet-per-minute (CFM)	Flow
85	cubic-meters-per-second (m³/s)	Flow
87	liters-per-second (L/s)	Flow
88	liters-per-minute (L/min)	Flow
89	us-gallons-per-minute (gpm)	Flow
135	cubic-meters-per-hour (m³/h)	Flow
79	cubic-feet (ft³)	Volume
80	cubic-meters (m³)	Volume
82	liters (L)	Volume
83	us-gallons (gal)	Volume
2	milliamperes (mA)	Electrical
3	amperes (A)	Electrical
4	ohms (Ω)	Electrical
5	volts (V)	Electrical
8	volt-amperes (VA)	Electrical
9	kilovolt-amperes (kVA)	Electrical
11	volt-amperes-reactive (var)	Electrical
12	kilovolt-amperes-reactive (kvar)	Electrical
15	power-factor	Electrical
122	kilohms (kΩ)	Electrical
34	watts-per-square-foot (W/ft²)	Power
35	watts-per-square-meter (W/m²)	Power
47	watts (W)	Power
48	kilowatts (kW)	Power
49	megawatts (MW)	Power
50	btus-per-hour (Btu/h)	Power
51	horsepower (hp)	Power
52	tons-refrigeration (tons)	Power
157	kilo-btus-per-hour (MBH)	Power
19	kilowatt-hours (kWh)	Energy
20	btus (Btu)	Energy
21	therms	Energy
22	ton-hours	Energy
146	megawatt-hours (MWh)	Energy
147	kilo-btus (kBtu)	Energy
27	hertz (Hz)	Frequency & speed
104	revolutions-per-minute (RPM)	Frequency & speed
39	kilograms (kg)	Mass & mass flow
40	pounds-mass (lb)	Mass & mass flow
44	kilograms-per-hour (kg/h)	Mass & mass flow
45	pounds-mass-per-minute (lb/min)	Mass & mass flow
46	pounds-mass-per-hour (lb/h)	Mass & mass flow
74	meters-per-second (m/s)	Velocity
77	feet-per-minute (fpm)	Velocity
0	square-meters (m²)	Length & area
1	square-feet (ft²)	Length & area
30	millimeters (mm)	Length & area
31	meters (m)	Length & area
32	inches (in)	Length & area
33	feet (ft)	Length & area
36	lumens (lm)	Light
37	luxes (lx)	Light
38	foot-candles (fc)	Light
70	days	Time
71	hours (h)	Time
72	minutes (min)	Time
73	seconds (s)	Time
95	no-units	General
96	parts-per-million (ppm)	General
97	parts-per-billion (ppb)	General
98	percent (%)	General
No units match that filter.

The codes above are the stable common slice — object types, property IDs, and units in this range don't get reassigned between editions. Only newer-edition additions and vendor extensions in the higher-numbered ranges need confirming against your device or ASHRAE 135.

BACnet object & property FAQ

What are BACnet object types?

The Object_Type enumeration — the numeric code in every Object Identifier that says what kind of point an object is. Type 0 is Analog Input, 1 Analog Output, 2 Analog Value; 3–5 are the binary trio; 8 is the Device object itself. BACnet Basics covers the object model.

What is property 85 in BACnet?

Present_Value — the live value of a point, and the property you read and write most. Property numbers are constant across object types, so 85 is Present_Value on an AI, a BO, or an MSV alike.

What do object types 128 and above mean?

Types 128–1023 are vendor-proprietary — a manufacturer can expose its own object types there. Unassigned numbers below 128 are reserved to ASHRAE for future editions of the standard.

How do I decode a packed BACnet Object Identifier?

The 32-bit Object_Identifier carries the object type in its top 10 bits and the instance in the bottom 22. Paste the raw value into the BACnet/IP Hex Converter's Object ID tab and it unpacks both.

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