BACnet Overview

BACnet, which stands for Building Automation and Controls network, is a protocol developed by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers). BACnet was developed as a response to industry concerns about increased networking of BAS components using proprietary communications methods. In the past, these proprietary communications severely limited the building owners' choices for system expansion, upgrade, and replacement. Every major controls vendor in North America, as well as academics, end users, consulting engineers, and government groups participated in its development.

BACnet has been accepted as an open standard by the American National Standards Institute (ANSI) and the European Committee for Standardization (CEN) standards. It is also an International Organization for Standardization (ISO) standard.

BACnet is designed to include all building systems, lighting, security, fire, heating, ventilation, and air conditioning. Its purpose is to promote interoperability - sharing data between systems made by different vendors.

It provides the necessary tools to develop a specification for systems that are interoperable. BACnet provides methods and standards for representing information, for requesting and interpreting information, and for transporting information. - ASHRAE SSPC 135


BACnet InternationalBACnet International


BACnet International is an industry association that facilitates the successful use of the BACnet protocol in building automation and control systems through interoperability testing, educational programs, and promotional activities. The BACnet standard was developed by ASHRAE and has been made publicly available so that manufacturers can create interoperable systems of products.  BACnet International complements the work of the ASHRAE standards committee and BACnet-related interest groups around the world. BACnet International members include building owners, consulting engineers and facility managers, as well as companies involved in the design, manufacturing installation, commissioning, and maintenance of control equipment that uses BACnet for communication.  For more information, please visit


Member of BACnet International logoBACnet International Membership


Members of BACnet International promote the successful use of the BACnet protocol in building automation and control systems.


Current member listing.


What is the BTL?

This is a BTL Listed ProductBACnet Testing Laboratories (BTL) was established by BACnet International to support compliance testing and interoperability testing activities and consists of BTL Manager and the BTL-WG.

General Activities of the BTL
The general activities of the BTL are:
      •    Publish the BTL Implementation Guidelines document,
      •    Organize the annual BACnet International sponsored Interoperability Workshop,
      •    Award worldwide BTL Listings to qualified BACnet devices,
      •    Support the activities of the BTL-WG,
      •    Provide support to the BACnet community with the help of the BTL-WG when questions arise on the testing package.
      •    Publish and Maintain the BTL Test Package with the technical support of the BTL-WG for use by pre-testers and approved BACnet testing laboratories.
      •    Approves Testing Laboratories for BTL Testing.

The BTL also provides testing services through its managed BACnet laboratory, SoftDEL.


What is the BTL Working Group


The working group was formed by BACnet International to oversee the establishment of the BACnet® conformance certification and listing program. The working group is comprised of members of BACnet® International and BIG-EU whose goals are to promote and maintain the BACnet® and BTL® trademark.

The BACnet Testing Laboratories Working Group provides oversight and guidance to the BACnet Testing Laboratories (BTL). The BTL Working Group is responsible for the technical aspects of BACnet International's testing and listing activities, the central goal of which is to improve BACnet interoperability between building automation products.

The BTL Working Group meets by phone usually once a week and has face-to-face meetings quarterly.

Click here to view BTL Working Group Charter.

How do I Join the BTL Working Group


Contact the Working Group Chairman for more information. 




BACnet Master Slave/Token Passing or MS/TP is used for communicating BACnet over a sub-network of BACnet-only translators. Each translator on the network has the ability to hear the broadcast of any other device on the network. The speed of an MS/TP network ranges from 9600 baud to 76.8K baud.


BACnet over ARC156


ARCnet is an embedded networking technology well suited for real-time control applications in both the industrial and commercial marketplaces. Its robust performance and the availability of low-cost silicon make it the network of choice in BAS's.

ARC156 is a unique implementation of ARCnet. ARC156 is similar to master slave/token passing (MS/TP). The main difference between the two is speed. ARC156 baud rate is 156K baud whereas MS/TP tops out at 76.8K baud.

Also, ARC156 uses a separate communications co-processor to handle the network traffic and a separate processor to handle the program execution. This provides faster processing of applications and handling of communications on the network. ARC156 is the standard communications method used by our translators.




PTP is used to connect two distinct BACnet networks so that information can be shared between the networks. PTP uses an EIA-232 connection between two BACnet half-routers. This connection allows for two different BACnet networks to speak to each other, even at different baud rates.