True building integration means finding commonalities between building systems and using the appropriate communication protocols to program them. This provides cooperative sequences of operations that offer increased value to the building owner. Before open architecture communications protocols, building automation was controlled by proprietary control solutions. Solution providers manufactured the building control systems, developed the application software, and charted product development, deployment and product line diversity.

Many building owners are now taking advantage of open systems communication technologies, creating a total building control network that includes every building system and breaking free from the sole-source lock, inviting competitive bidding and making best-in-breed product selection, according to Strata Resource Inc., Albuquerque, N.M., a market research company that specializes in analysis of building automation technology, companies, trends and products. The three major protocols in use today, BACnet, LonWorks and Modbus, provide electrical contractors with opportunities to broaden service offerings, help building owners achieve their integration and energy goals and add value.

BACnet

The Building Automation and Control Network protocol (BACnet) began its development in 1987 under the auspices of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), Atlanta. It was designed specifically to meet the communications needs of building automation and control systems for applications such as heating, ventilating and air conditioning (HVAC); lighting; access control and fire detection systems; and the systems’ associated equipment.

“BACnet provides a framework and set of standardized objects and services to allow manufacturers to model the physical devices and their properties on a network,” said Rich Westrick, director of engineering for Synergy Lighting Controls, Conyers, Ga., an Acuity Brands company.

As an entirely open, standardized and nonproprietary protocol, BACnet permits complete interoperability between different manufacturers’ building automation control products and access to information, control and programming capabilities from a single-user interface, said Terry Hoffman, director of Building Automation System (BAS) marketing for Johnson Controls, Milwaukee.

“BACnet fosters integration between building systems and components from multiple vendors into a single, interoperable network,” he said.

For the building owner, the benefit of BACnet is the freedom to choose the vendors it wants, to change vendors in the future, and to have a truly integrated building system (IBS). For the manufacturer, the benefit is confidence that the equipment it provides for a project will be interoperable with the rest of the automated building system.

The electrical contractor benefits from the flexibility that BACnet affords in running fewer wires to each individual building system.

“With fewer wires to run, the contractor saves thousands of feet and dollars in cabling,” said Jon Williamson, product marketing manager for TAC, Carrollton, Texas.

LonWorks

The LonWorks protocol, EIA/CEA 709.1-B-2002, is a networking platform specifically created to address the unique performance, reliability, installation and maintenance needs of system control applications. The platform is built on the protocol created by Echelon Corp., San Jose, Calif., for networking devices over media such as twisted-pair cables, power lines and fiber optic cabling.

“LonWorks is more than just a communication protocol. It is an entire set of related technologies that allow any number of electronic devices or products to work together, communicate and act as a system,” said Steve Nguyen, Echelon’s director of corporate marketing.

Echelon introduced the LonWorks technology in 1990 and it was initially adopted primarily in building automation, HVAC and some light industrial applications. In the mid-1990s, LonWorks introduced interoperability that would allow different controls manufacturers’ products and systems to communicate over the nonproprietary, open-architecture platform. By 2006, approximately 60 million devices had been installed with LonWorks technology. Manufacturers in a variety of industries including building, home, transportation, utility and industrial automation have adopted the platform as the basis for their product and service offerings.

The Echelon “Neuron chip” was initially the only way to implement a communication node, and it is used in the large majority of LonWorks-based hardware. More recently, the LonWorks protocol has been made available for general--purpose processors, but the development has not yet been widely adopted. As an open architecture, LonWorks also provides building owners with freedom of vendor choice.

“LonWorks’ ability to manage different vendors’ products is the key to creating and delivering the value of interoperability,” Nguyen said.

LonWorks’ interoperability is governed by the LonMark International Group, which maintains the interoperability guidelines, creates standard applications and tests and certifies products.

Modbus

Modicon, now part of Schneider Electric, Palatine, Ill., published Modbus in 1979 for use with its programmable logic controllers (PLCs) in industrial applications to read data and to program control systems. According to Fred Cohn, director of network strategy for Schneider’s automation business unit, Modbus has evolved into a publicly accessible data communications protocol used with many different media, such as serial, Ethernet and various wireless technologies in both industrial and commercial applications.

“Modbus is widely used today for connecting building management systems to intelligent HVAC, lighting and power distribution and monitoring systems,” he said.

Modbus has become universally accepted because of its openness, simplicity, low-cost development and the minimum amount of hardware required to support it. Several hundred Modbus-compliant devices are already available in the market and more are being developed each year. As a well-defined and published international standard, Modbus provides interoperability between different manufacturers’ devices when applied properly.

“Modbus allows facility managers to locally or remotely access data regarding building operations, equipment status and energy consumption. It is a simple protocol to develop from the device standpoint and simple to implement from a software standpoint,” Cohn said.

Modbus can also be cost-effective to implement because it is media-independent. The protocol is used in multiple master/slave applications to monitor and program devices, to communicate between intelligent devices and sensors and instruments, and to monitor field devices using personal computers and human-machine interfaces. Although originally developed for industrial applications, the protocol is now used in building, infrastructure, transportation and energy applications.

Similarities and differences

All three protocols are the similar in that their primary purpose is to facilitate communication between devices in a building. Another common thread is that they all conform to European Open System Interconnection standards and provide a migration path for data to be communicated to higher level devices.

According to Nguyen, the fundamental difference between the protocols is that BACnet was developed as a system-to-system interoperable protocol originally designed for HVAC systems to communicate with each other, while LonWorks was developed as an interoperable protocol at the product and device level.

“Both seek to implement an integrated building and to ease its management,” he said.

Another primary difference between BACnet and LonWorks is that the BACnet standard does not include hardware, while the LonWorks protocol is embedded in its neuron chip.

“However, all three protocols allow the user to avoid being locked into a single vendor and to create a truly automated and integrated building,” he said.

According to Hoffman, BACnet, LonWorks and Modbus all differ in their approach to how their target customer base might choose to implement integrated systems and devices.

“Modbus supports a more industrial methodology, BACnet focuses on the integration of multiple buildings that are, for the most part, stand-alone, and LonWorks is used to integrate many small, intelligent devices arranged into groups that represent functions, buildings or even geographic areas,” Hoffman said.

However, there’s nothing stopping a building owner from employing two or even three of the protocols to obtain the strengths and benefits of each.

For instance, Modbus differs from the other two protocols in its simplicity, according to Dave Robin, senior research engineer, Automated Logic Corp., Atlanta.

“One of Modbus’ primary strengths is that it is a master/slave protocol which means one device is set up to gather data, and the other devices provide the data,” he said.

However, while Modbus is simpler to implement, it is not as sophisticated a protocol and does not address scheduling, alarming and trending issues as BACnet and LonWorks do.

What these protocols mean to the electrical contractor is having a standard that allows them to be confident that the specified equipment on a project will interoperate.

“If, for example, the designer or integrator specifies BACnet equipment, the contractor can focus on installation and not worry about the coordination of interfaces or gateways to tie proprietary networks together,” Westrick said.

According to Robin, a single communication standard allows the contractor to think of the building as a single entity.

“A single protocol greatly simplifies network design, reduces installation and wiring costs and reduces installation time,” Robin said.

Nguyen said that since a protocol like LonWorks doesn’t require electrical contractors to have proprietary knowledge of various manufacturers’ equipment, it can perform work in an IBS that was performed by specialty contractors in the past.

“The contractor still has to learn the best methods for wiring an open architecture communications platform, but doesn’t need extensive knowledge of network topology to succeed,” he said.

Wireless is the next step in IBS communication, according to Williamson and will be used in some, but not all, applications.

“ASHRAE is already working to extend BACnet to support wireless Zigbee networks,” he said.

Another future area to explore is cost-effective, small device networking.

“The market is moving toward lower cost, smaller device communication. The area that offers the best opportunity is deploying low-cost wireless and powerline communications for cost-effectively integrating simpler devices,” Cohn said.

BREMER, a freelance writer based in Solomons, Md., contributes frequently to ELECTRICAL CONTRACTOR. She can be reached at 410.394.6966 or darbremer@comcast.net.