Building Management Systems: Yesterday, Today and Tomorrow

Building Management Systems: Yesterday, Today and Tomorrow

Integration holds great potential, but faces obstacles such as proprietary standards. Vinayak Sane, Principal Consultant for Elmark Engineers, examines open systems for building automation.

A building automation system (BAS) optimizes the administration, operations and performance of building systems with purpose-built networks and protocols. A good BAS greatly increases the interaction of mechanical subsystems within a building, improves occupant comfort, lowers energy use and allows off-site building control.

Modern systems use computer-based monitoring to coordinate building control subsystems such as security, fire/life safety or elevators. Over the years, several proprietary building automation network standards have evolved in the marketplace.

Proprietary solutions have permeated the nonresidential HVAC market, limiting upgrades or expansion to off-the-shelf vendor-specific products or costly custom solutions. Vendor initiatives to publish proprietary protocols resulted in one-way systems, with the host system playing the role of master.

The proprietary or legacy systems consisted of digital direct control (DDC) controls looped in a daisy chain. The interconnection between them used to be peer-to-peer or a supervisory controller communicating to set of DDCs in a star format. This would require large amount of cabling.

Proprietary system architecture has its limitations when integrating multiple utilities. Closed systems mean the client is at the mercy of the vendor, who dictates price and products for a seamless interface.

Systems Today
Flexibility and scalability are important when selecting a BAS. The ability to reconfigure and monitor changes in real-time is important to building managers. For users, BAS enables different systems to talk to one another and integrate all building functions into one seamless system. The development of open communication protocols for building automation makes that dream a reality, with significant benefits for end users.

Open systems provide enhanced usability, lower installation costs and greater control of life-cycle expenditure. Open systems allow products with the best capabilities to be chosen for the task at hand. The result is a more effective BAS solution, which is not held back by proprietary software.

In recent years, open protocols like BACnet or LonWorks have been implemented as primary system protocols instead of proprietary ones. Some organizations have taken the lead in defining vendor-independent open systems.

LonWorks can interface with a wide range of systems, from hotel booking to home automation. It is probably the most common open system found in modern buildings. In its original implementation, LonWorks could be considered proprietary; use of the hardware and software required a licensing agreement from Echelon. Since then, Echelon has allowed users to port the LonTalk protocol to different hardware platforms.

BACnet, a data communication protocol for building automation and control networks, is a fast-growing and freely distributed, garnering the most interest from the U.S. and Asia. New products are appearing regularly from multiple vendors, as the protocol operates over a wide range of communications media. It is independent of hardware or software, making it suitable for many applications. BACnet is a software-only solution which integrates products from different manufacturers. It consists of a standardized set of messages that replaces the proprietary messages between the field panels and the host.

Compared to BACnet, LonWorks is a lighter protocol, suited for smaller and more cost-effective devices.

LonWorks represents a complete hardware and software solution for control network communication. The hardware platform was based on the Neuron chipset, which provided I/O processing and data communications. Software is based on the LonTalk communication protocol, which provides a set of standardized messages and a development tool for custom applications. It does not allow the use of IP as the transport layer. Therefore, for remote management over an IP network, clients must use a gateway encapsulating LonTalk in IP or HTTP servers displaying LonTalk device information over IP. Manufacturers need to pay license fees to Echelon to integrate Neuron chips into their devices

BACnet and LonWorks are not interchangeable. Each protocol provides its own standardized set of messages. BACnet messages can be transmitted across a LonWorks communication backbone, but messages between LonWorks and BACnet are not compatible.

LonWorks and BACnet complement each other in an open system. For example, a BACnet user may want to incorporate LonWorks devices. In this case, LonWorks can easily be added for a higher level of interoperability.

Among the common protocols Modbus, N2, LonMark and BACnet, only BACnet is developed in an open manner. Native BACnet means systems work seamlessly with third-party BACnet devices without protocol converters, saving on system configuration and ongoing maintenance.

While all the protocols above offer data sharing for read-write points, BACnet and LonMark go further with device management. They offer scheduling, trending, and alarm and event management — but BACnet is more powerful than LonMark. BACnet systems provide users with single-seat control of an entire facility through a dedicated front end or remotely by Web browser.

A fundamental aspect of a converged and intelligent system is transparency. If the system is to maintain control and reduce costs, it must have a common platform. While this does not preclude sophisticated management software, a simple interface such as a Web browser can deliver a user-friendly platform to realize a powerful system. This approach allows the cabling infrastructure to be fully utilized, removing the need for proprietary cabling or IT installations.

Buildings need a simpler, more cost-effective means of managing diverse proprietary control systems. At the same time, Internet technologies have been developed at an explosive rate, speeding data collection on the Internet. Real-time information optimizes the performance of buildings, productivity and the bottom line.

The International Standards Organizationadopted the BACnet protocol as a communications standard for integrating building automation and control products.

The best network for interoperability would be one that relies on LonWorks at the unitary level and BACnet at the building level, with a Web browser for the interface.

Today, a BAS can send alarm information to smart phones and computers. Mobile building managers can check systems remotely and react more quickly to problems. Using an existing network also reduces installation costs and increase scalability.

Systems of Tomorrow
As infrastructure expands horizontally and geographically, IT managers look for a communication medium with more bandwidth. Wireless networks provide ease of connectivity in any application.

Ethernet is one of the approved LAN types in the BACnet standard ANSI/ASHRAE Standard 135-2001. With the newer BACnet/IP LAN type defined, and more building owners using Web browsers to view the status of their buildings, interest in Ethernet is growing.

A TCP/IP Ethernet network connects to a Web browser easily, but there is more to using Ethernet. Instead of using coaxial cable with transceivers mounted in ceilings, Ethernet uses inexpensive twisted-pair or fiber-optic cabling to connect Ethernet stations. Recommendations on cabling and connectors for commercial buildings can be found in standards such as ANSI, TIA or EIA-568-B.

The original Ethernet data rate of 10 Mbps still is supported, but some newer equipment can automatically configure a station to operate at either 10 or 100 Mbps.

Originally, Ethernet operated only in half-duplex mode, which allowed transmissions in both directions, but not at the same time. Now with twisted-pair and fiber-optic cabling, which have two distinct paths for signaling, it is possible to configure Ethernet stations to operate in full-duplex mode with simultaneous transmission and reception over separate paths.

With the migration of LAN to wireless LAN in closed environments, BAS vendors are upgrading their systems with Ethernet connectivity.

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