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One of the biggest changes in building control systems over the past two decades has been the wider use of open or standard protocols. These protocols are essential to making buildings more intelligent, since they enable building systems and devices from different manufacturers to interoperate — that is, to be able to communicate and work with each other. A system that uses open or standard protocols gives facility managers the flexibility to use products from different manufacturers and promises long term cost savings. But it’s not enough to ask for a specific protocol. Whether it’s BACnet, LonWork or Modbus, you have to take the right steps to be sure of getting what you want.
BACnet is a standard protocol introduced by ASHRAE in 1995. It is a written specification that is an ANSI national standard and an ISO international standard. According to BACnet International, the purpose of the protocol is “to standardize communications between building automation devices from different manufacturers, allowing data to be shared and equipment to work together easily.” For more about BACnet, click here.
LonTalk, developed by Echelon, is a standard protocol, and an ANSI and ISO standard. According to Echelon, the LonWorks “standard and technology encompasses all the elements necessary to design, install, monitor, and control a network of diverse devices.” Among the microprocessors that can be used to implement LonWorks is the Neuron chip, which was designed by Echelon and includes the LonTalk protocol. For more about LonWorks, click here.
Modbus was developed in 1979 by Modicon, now Schneider Electric. It is an open protocol, primarily “used to establish master-slave/client-server communication between intelligent devices,” according to The Modbus Organization, an independent, member-based non-profit organization that now supports the protocol. Other variations of Modbus allow for communications over an IT network.
For an overview of all three protocols, see BACnet, LonMark and Modbus: How and Why They Work.
The use of open protocols is growing. “Where there are (new construction) projects, we definitely see the tendency to go with open systems,” says Konkana Khaund, industry manager with the energy and environmental practice, Frost & Sullivan. She sees the same trend in the equipment replacement market. "Whenever there is an opportunity to replace, people are definitely looking at solutions where they can incorporate more and more open solutions.”
No single protocol is the best for every application, say experts. All three are widely used. According to a Building Operating Management survey in 2011, 62 percent of respondents had at least one BACnet application; for LonTalk the percentage was 40 percent, while for ModBus the number was 30 percent.
BACnet, LonWorks and Modbus: Getting What You Want