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BACnet Networking Guide


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BACnet Networking Guide

  1. 1. F-27360 MicroNet BACnet Wiring and Networking Practices Guide 2-1 Chapter 2 Networking Practices Introduction to BACnet In BACnet systems, BACnet devices use BACnet objects to share data. To allow this sharing of data, a BACnet network must be properly configured. On a properly configured network, the BACnet protocol carries these data and uses Ethernet®, Internet Protocol (IP), and Master Slave Token Passing (MS/TP) for network communication. At the device level, MS/TP network trunks connect individual BACnet compliant controllers. Architecture Overview Introduction As implemented in an I/A Series MicroNet BACnetwork, the BACnet architecture uses one or more networking protocols to allow communication among controllers and engineering tools. At the device level, Master Slave Token Passing (MS/TP) networks can be used to connect up to 127 unitary or VAV controllers and MS/TP tools to a Plant Controller. With 127 devices connected to a Plant Controller, all 128 MS/TP addresses on the Plant Controller are used. Similarly, up to 31 devices (unitary, VAV, Plant Controller, or MS/TP tools) can be connected to each of the two network trunks of a UNC 510-2. Multiple BACnet MS/TP networks can be connected by networking the Plant Controllers and UNCs using BACnet over IP or BACnet over Ethernet. This is referred to as a BACnet internetwork. In such a configuration, the Plant Controllers and/or UNCs manage communication throughout the internetwork and serve as routers. Engineering tools can be used to manage controllers throughout an internetwork by connecting them to an MS/TP network trunk or by connecting to the IP network. Figure-2.1 shows a BACnet internetwork comprising four or five individual networks. There are thee individual MS/TP network trunks, each managed by a UNC or Plant controller and running individual BACnet devices. Ethernet or IP can be used as the networking technology for the backbone, adding a fourth network. If appropriate for the installation, both Ethernet and IP can be used on the network backbone. This would add a fifth network to the internetwork as shown in Figure–2.1.