Building peripheral devices communicate with one or more central control systems to manage energy consumption data, building comfort levels and other building operations. These devices transmit and receive data through specific communication protocols. There are several protocols in wide use, each with specific applications. When control systems use different protocols than the device , or when multiple control systems using different protocols want to access the same devices, protocol conversion is needed to enable data integration.
Commonly Used Protocols
The first protocol language, called Modbus, is an open communications protocol that has long been the popular communications protocol for energy management systems and many other applications. It is most often used over RS-485 serial links (known as Modbus RTU), however an Ethernet implementation, Modbus TCP is available as well.
Another language, called BACnet, is an open communications protocol that is in wide use in building automation systems software. Many BAS peripheral devices, such as CO2, temperature sensors, and valves and actuators can communicate via BACnet protocol. It is often the software of choice for the central building control system.
Simple Network Management Protocol (SNMP) is an internet-standard protocol for managing devices on IP networks. SNMP is often the preferred communications protocol of data center managers. Data is easily viewed from any device in their enterprise that supports SNMP using common software tools known as MIB browsers. They can also easily incorporate data from those devices into other software or scripts using the information provided in the MIB files.
Protocol Conversion Applications
A mixed-use building, such as a commercial office space or data center, often includes devices that communicate using more than one of these protocols.
Typically, the commercial office building control system uses BACnet software. This language is convenient for creating reports, since BACnet devices are easy to poll for recent data. When polled by the controller, all devices transmit their data, as well as other information, such as the device type and location in the building. However, the energy meters placed in the panels are commonly Modbus devices. This problem is easily solved by installing a Modbus-to-BACnet protocol converter between the meter and the controller. The converter allows the data from the energy meters to be accessed simultaneously by both a building automation system and an energy management system, avoiding the need for redundant metering hardware or to complex data sharing between two disparate systems.
The same Modbus energy metering devices can be used to monitor the energy use of components in the data center. The protocol converter is installed to translate this data into the SNMP protocol. In this application, this converter allows data from the energy meters to be accessed simultaneously by both the data center manager with their SNMP tools and an energy management system.
Commercial Office Space Application
Data Center Application Example
Using these protocol converters, the data from all devices throughout the building can be unified into a single, real-time picture of the total energy usage for the building.
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