Automation Glossary • BACnet

What Is BACnet?

Merobix Engineering • • 4 min read

BACnet (Building Automation and Control Networks) is the dominant open protocol for building automation systems - HVAC, lighting, access, and energy metering. Standardized as ASHRAE 135 and ISO 16484-5, it gives building controllers from different vendors a common language, and it increasingly overlaps with industrial SCADA at facility level.

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BACnet in one line: BACnet is an open building-automation protocol (ASHRAE 135 / ISO 16484-5) that models devices as standardized objects (such as Analog Input or Binary Output) and defines services to read, write, and subscribe to their properties over data links including BACnet/IP and MS/TP.

Objects, Services, and Data Links

BACnet represents everything as objects with properties. An analog sensor is an Analog Input object; a controllable damper is an Analog Output or Binary Output; there are also objects for schedules, trend logs, calendars, and alarms. Each object has properties like Present_Value, Units, and status flags. Services then act on these objects - ReadProperty and WriteProperty for point access, and change-of-value subscriptions (COV) so a client is notified only when a value changes rather than polling constantly.

BACnet runs over several data links. BACnet/IP carries the protocol over standard Ethernet and UDP/IP, which is now the common choice for controllers and supervisory systems. BACnet MS/TP (Master-Slave/Token-Passing) runs over RS-485 twisted pair for lower-cost field controllers, similar in spirit to other serial fieldbuses. A BACnet/IP-to-MS/TP router bridges the two.

BACnet and Industrial SCADA

BACnet lives in the building-services world, but it meets industrial SCADA wherever a facility's mechanical and electrical systems matter to operations - control-room HVAC, equipment-shelter cooling on remote sites, data-center facility monitoring, and building energy metering. Because it is object-oriented and self-describing, mapping BACnet points into a SCADA tag database is straightforward once a driver or gateway can browse the device.

For unified monitoring, operators often want building-automation data alongside process data in one place. A cloud SCADA can ingest BACnet points either through a native BACnet/IP driver or a gateway that republishes them over a common protocol. Merobix supports BACnet among its device protocols, so facility HVAC, metering, and equipment-shelter data can share the same dashboards, alarms, and historian as process telemetry - useful for remote wellsites and processing plants where keeping equipment within temperature limits is operationally critical.

Frequently Asked Questions

What is the difference between BACnet/IP and BACnet MS/TP?

BACnet/IP carries BACnet over standard Ethernet and UDP/IP and is used for supervisory systems and higher-end controllers. BACnet MS/TP runs over RS-485 twisted pair for lower-cost field controllers. A BACnet router bridges the two so they form one logical network.

Is BACnet an open standard?

Yes. BACnet is an open, vendor-neutral standard published as ASHRAE 135 and ISO 16484-5. That openness is why controllers from different building-automation vendors can interoperate on the same network.

Can SCADA read BACnet points?

Yes. A SCADA platform with a BACnet driver can browse a device's objects and read or write their Present_Value and other properties over BACnet/IP, or read them through a gateway. This lets facility HVAC, metering, and equipment-shelter data appear alongside process telemetry.

From Definitions to a Live Dashboard

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