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Security

A key concern many enterprise professionals raise about wireless-transmission technology relates to security. Because wireless signals travel over the air, access to information cannot be secured physically, as with traditional cable. This gives many people the false impression that wireless technologies are highly vulnerable to attack. In reality, with proper authentication and encryption technology, wireless transmission is just as secure as, if not more secure than, wired networking. Without a physical cable to splice into, signals are difficult to intercept. Therefore, it is important to choose a wireless product that employs standard encryption and authentication protocols to ensure the highest level of security. Most state-of-the-art wireless solutions incorporate these standards.

Interoperability

Interoperability is the ability of devices that follow a certain technology and standard to work and communicate seamlessly together to fulfill a specific application, regardless of manufacturer. The tools used to configure and commission a system should be interoperable, allowing integrators to replace system devices with products from other manufacturers. The interoperability of wireless components from different manufacturers is questionable with regard to certain wireless technologies and standards.

Building owners have voiced the need for interoperable devices. (For example, it would be convenient if a thermostat from one company could communicate with a wireless-compliant intelligent controller from another company.) If a technology or standard does not allow the replacement of a device from one manufacturer with a device from another manufacturer, the solution becomes locked in, and the end user is forced to buy products from a single source.

Maintenance

Because power requirements of various wireless devices differ, sensors powered by batteries must be monitored constantly for battery condition. Preventive battery-replacement cycles assuming worst-case battery life help avoid this problem, but also cause more frequent battery changes, leading to increased costs and toxic waste. Also, it takes considerable logistical effort to stock and properly dispose of batteries and log service cycles. Battery-driven maintenance is amplified with added features, such as mesh networking, which add complexity, require significant power, and lower battery life. Integrators often are forced to predict needs and find balance between radio performance and battery/maintenance considerations.

WHAT IS IN IT FOR A BUILDING OWNER?

The initial demand for wireless solutions often is problem-driven. If a project or installation does not allow for easily accessible wire runs to control points, a wireless solution may be needed. For example, facilities with multiple buildings might require tunneling under existing driveways and parking lots to install wire runs. In retrofit situations, it is difficult, if not impossible, to run wire to all parts of a building. These types of situations present opportunities for wireless solutions.

Integrating the disparate systems of a building into a coherent communication and control infrastructure long has been a goal of facility engineers. However, completely connected facilities remain a challenge because wireless-system integration is not always straightforward. As previously mentioned, some wireless technologies use a significant amount of power, requiring frequent battery changes and causing maintenance issues. Also, wireless networks can be a concern when frequency bands become overcrowded. However, with sensor-placement flexibility, relocation feasibility, and reliable operation, facilities executives can consider wireless technology an option to solve problems in existing plants or for deployment in new facilities.

WIRELESS-SYSTEM INTEGRATION

From a general topology and infrastructure point of view, there is no significant difference between HVAC control systems in industrial and commercial buildings. However, because the buildings' construction characteristics and controlled-zone sizes are different, point-to-point distance control and sensor information has to travel. Network architecture generally should be kept flat, meaning the number of network communication levels should be kept to a minimum.

On the field level of a BAS, the requirements for wireless communications are relatively simple. Sensors, intelligent control units, and actuators operate in proximity and communicate relatively infrequently with little data. Therefore, they do not require high communication bandwidth. Self-powered low-energy radio sensors are most appropriate for these types of applications. Because ambient conditions in a building change slowly, related sensor readings and transmissions can occur in minutes. This allows a solar-powered sensor device, for example, to operate with minimal power and to store excess light energy in a supercapacitor for later use.

AVOIDING WIRELESS-INSTALLATION PITFALLS

It is a good idea to compare retrofit projects with similar sites using the same radio-frequency test-equipment recommendations. A radio-frequency site survey can be conducted to identify possible interferences caused by machinery or other radio devices.

The deployment of all radio components should be planned properly, following the installation and range-planning guidelines provided by the technology supplier. Before physical installation work begins, blueprints of the building, including locations of production equipment and furniture, should be analyzed. This kind of survey can help identify the parts of a building that prevent the propagation of radio waves, such as elevator shafts, fire-protection walls, and staircases. This engineered approach can predict the ideal placement of remote radio-sensor devices with regard to building-system access points.

Wireless equipment should be installed after construction is finalized — once power cabling, conduits, and ducts have been established — to avoid possible radio-path obstructions. This is particularly important for wireless infrastructure equipment, such as routers, repeaters, and gateways to the central building system. It is important that mechanical engineers, control contractors, and other stakeholders communicate before construction begins. In a retrofit situation, there is not much that can be done about mechanical installations. A wireless integrator has to work around given obstructions by placing radio components in the best possible locations and, if necessary, using additional radio-range extension components, such as repeaters, to create a communication bypass.

President and founder of Koenig Consulting, an independent industry representation and consultancy company specializing in sustainable and energy-efficient building-automation solutions, Volker Koenig has 25 years of experience in systems engineering and is an expert in control networks. An applications engineering manager for EnOcean Alliance, Eugene You has experience in radio frequencies, switching-mode power supplies, and industrial automation.

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