BACnet, short for Building Automation and Control Network, is a communication protocol used to connect and manage devices in building systems like HVAC, lighting, security, and more. It’s a universal language that lets different equipment, even from different manufacturers, talk to each other and work together seamlessly. This open standard makes it easier for building operators to integrate and control various systems in a streamlined way, helping to improve efficiency and reduce operational headaches.
Well, Ethernet, IP, and MS/TP are the ways that BACnet devices can communicate with each other. Think of these as phone calls, emails, and text messages: they’re speaking the same language, but not using the same mediums. You can have a mix of BACnet IP, MS/TP, and Ethernet in your building. BACnet supports various applications such as access control, air conditioning, lighting control, and fire detection systems. So, how exactly are they different?
The key difference between them lies in how they transmit data and their use cases:
- BACnet over Ethernet uses Ethernet as the physical layer for communication. Devices on the same Ethernet network can communicate directly, but this method is mostly used for local networks and doesn’t handle routing between different networks well.
- BACnet/IP is the more flexible version, using standard IP protocols (like the ones used for the internet) to communicate across different networks, including both local and wide area networks. It’s great for larger setups where devices may be spread across multiple locations because it supports routing.
- BACnet MS/TP (Master-Slave/Token Passing) is a slower, older method that uses twisted-pair cabling (like RS-485). It’s typically used for smaller networks, such as connecting field devices like sensors or thermostats, because it’s more cost-effective for low-speed communications but doesn’t scale as easily as IP-based options.
Each serves a different purpose based on the scale and complexity of the system.
Our video below is a great primer.
Is BACnet The Same as Ethernet?
Ethernet and IP are relatively similar, as they aren’t dependent on token passing. The important thing to remember is that Ethernet communicates across the control network based on MAC addresses, while IP communicates based on IP addresses. Additionally, Ethernet isn’t routable, so devices have to be on the same subnet to communicate with each other. IP is routable but requires a BACnet Broadcast Management Device (BBMD) on each subnet to send messages across the network. So, you’d likely use Ethernet if you only need to communicate between subnets and would use IP to communicate across the network. This thread from HVAC Talk is very helpful for understanding the differences between IP and Ethernet.
The BACnet committee plays a crucial role in developing and maintaining the BACnet standard for building automation and access control networks.
BACnet Testing Laboratories (BTL) ensure that products claiming conformance to the BACnet standard have been independently tested using industry-accepted test definitions.
For more information, this article from Phil Zito’s Building Automation Monthly digs into IP and MS/TP and the different network layers.
Want to know more? Check out our Ultimate BACnet FAQ.
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