Due to the proliferation of tough commercial building energy codes and green construction, automatic energy-saving lighting control devices and systems are now common in new buildings.
A typical lighting control solution features an actuator, such as a relay, that controls the load and is paired to an input control device, such as a sensor, switch or dimmer. The input device and the actuator are often connected through low-voltage wiring used for communication of information or commands.
In existing buildings, justifying the installation of solutions requiring low-voltage wiring becomes problematic when one considers the cost and obstacles, such as inaccessible or hard ceilings, asbestos abatement issues, and wide fixture spacing. In these applications, providing good control functionality, while eliminating the requirement for new wiring, has obvious benefits. As a result, wireless control technology, having already achieved popularity in residential applications, is beginning to find its place in the commercial building market, making a range of energy-saving lighting solutions possible and potentially more financially attractive. “Wireless” may include powerline and infrared but most commonly refers to radio frequency-based systems in which devices communicate using radio waves.
This approach promises a number of benefits compared with hardwired solutions. First is flexibility; devices can be placed where needed, installed faster and moved more easily. Electrical planning may be shortened, and irregular applications can be better served. Second is cost savings; dedicated control wiring and associated switch legs, traveler wires and other materials are not needed. Third is less disruption to business operations, with no damage and subsequent repairs to walls and ceilings.
The commercial market
Wireless radio frequency (RF) lighting control started in residential applications, but it is becoming well-positioned for commercial applications.
“The biggest change in the last two to three years is proliferation and acceptance of wireless devices entering the market,” said Rich Black, director of residential product management and business development for Lutron Electronics Co. “For electrical contractors, retrofittable, wireless lighting controls present an opportunity to sell systems into existing homes and offices as well as new homes and offices.”
“With the growth of wireless technology, the cost of radio technology has now reached a point where it is affordable to manufacture wireless lighting control products and not destroy the overall return on investment of the luminaires with controls,” said Mike Crane, product manager for Hubbell Building Automation. He added that wireless control protocols now enable quick response times for lighting systems, so lighting can switch or dim almost instantly after a control command has been initiated.
“Wireless RF lighting control has become more reliable over the past 10 years,” said Brian Carberry, director of product development for Leviton Lighting and Energy Solutions. “There are now more wireless solutions available than at any time before.”
The inclusion of wireless RF lighting controls in many utility rebate programs is a sign of growing acceptance.
“For control rebates specifically, the biggest shift we notice is that many rebate programs are starting to rewrite their program guidelines to allow wireless sensor technology,” said Leendert Jan Enthoven, president of BriteSwitch, LLC, a company that specializes in rebate fulfillment.
Systems and approaches
Wireless RF lighting control devices include occupancy sensors, photosensors, low-voltage relays, line-voltage actuators, plug controls, hotel card switches, shade controls and more. Some manufacturers have developed the technology around niche solutions, such as parking garages and outdoor lighting.
“As the technology becomes more pervasive in the commercial market, major manufacturers will focus on being one-stop shops by providing complete solutions for all lighting applications. These bundled solutions will include all forms of luminaires with wireless controls built in,” Crane said.
The actuator may be installed at a junction box in or on a lighting fixture. Or, with the advent of solid-state lamps, the lamp can provide intensity and, in some cases, color. The input control device will install where it normally should and may include smart devices, such as phones and tablets.
These elements communicate within range using radio waves exchanged between transmitters and receivers. The input- control device operates using either battery power, a power pack or energy harvested from the environment, such as ambient light. Obstacles, such as walls and partitions, may limit range. Repeaters, which boost signal strength, may expand range.
Communication may be one- or two-way (peer-to-peer). For example, after receiving a command, a device might transmit a receipt. If the original transmitter does not get a receipt, it can try again, which increases reliability. Two-way communication also presents possibilities for monitoring and control.
The devices may be configured as a fixed or mesh network. In a fixed network, communication devices (repeaters) provide RF coverage for all devices with a constant message route. In a mesh network, devices communicate with each other as nodes in a network; a signal generated by one device is routed through others in the most efficient path until it reaches its target. Mesh networks also are self-healing—if a node fails, the control signal will route through other devices, which promotes reliability but, potentially, at the expense of response speed.
In a typical control system, devices intended to work together are wired. With a wireless system, they must be programmed and mapped. In a fixed network, the contractor will typically put the actuator into a “learn” mode and pair it to the switch. For mesh-based systems, the devices must be mapped; software may be used to communicate to an access point or gateway device, which discovers and pairs devices.
“When working with mesh-based systems that have unique addresses for each device, it’s imperative that the address information provided with each device is not discarded but properly recorded on site plans or as-builts. Having this information available is key to [successful system commissioning],” Crane said.
Both fixed and mesh network approaches are readily scalable. Large systems, however, may require special care in application and setup, Carberry said.
“These systems can be very challenging scenarios that require a better understanding of existing site conditions, existing controls, and the needs of the occupants before the correct products can be specified effectively,” he said.
“Wireless systems have to have devices that can repeat messages and route them via different paths,” Crane said, speaking about larger systems. “This ensures that messages will still get to their target destination even if one or more paths may be unavailable for whatever reason, such as an inoperable node in a path.”
Another lesson learned, he said, is that large wireless lighting applications need a way to uniquely identify each device. He warned against addressing dip switches or knobs, which can support a smaller number of addresses, limiting the number of luminaires and input devices they can control. There are now wireless protocols that support unique addresses associated with each radio.
For devices within a wireless RF lighting control network to be interoperable, they must be compatible with the same protocol, e.g., ZigBee, Z-Wave, EnOcean, synapse network appliance protocol (SNAP), Bluetooth and proprietary protocols.
ZigBee is a 2.4-gigahertz (GHz) protocol supported by the ZigBee Alliance of manufacturers. As an open-source protocol (IEEE 802.15.4), it offers interoperability between products made by different manufacturers. It supports mesh networks with two-way communication between devices. With a long device range of 200–400 feet and increased device counts, it is well-suited to commercial buildings. The protocol recently expanded to include a ZigBee PRO Green Power feature, which enables wireless controls to become powered by energy harvesting sources rather than batteries or alternating current (AC) mains power. The downside to ZigBee is the 2.4 GHz band is heavily trafficked.
“Coexistence has always been a problem and continues to be,” Carberry said. “Open-frequency bands are becoming congested with wireless traffic from systems such as WLAN, ZigBee, Bluetooth, wireless microphones, wireless cameras, smartphones and even microwave ovens. The solution, in the past, has been to boost power, but this only means you are shouting louder and drowning out all other wireless devices. The smart solution is to adapt and use the frequencies smarter.”
Some manufacturers favor less-trafficked frequencies, such as 315, 400 and 900 megahertz (MHz). Z-Wave (915 MHz), developed by home control manufacturer Zensys and shared with partnering companies through the Z-Wave Alliance. However, it has been limited to residential and light commercial applications due to limited range (35–50 feet) and lower device count.
EnOcean (315 MHz), developed by EnOcean and shared with partnering companies through the EnOcean Alliance, was designed around the company’s proprietary energy harvesting technology. For example, ambient light or the mechanical energy produced by the flip of a wall switch is harvested to produce a control signal. Device range is good (100 feet). Higher device counts are supported, but communication is one-way.
SNAP (900 MHz) provides the infrastructure to create peer-to-peer, self-organizing and self-healing mesh networks.
“SNAP supports 900 MHz radios, while ZigBee supports 2.4 GHz radios,” Crane said, adding that the major difference is that, “900 MHz provides almost twice the radio coverage and is least affected by propagation losses due to penetration through obstacles, diffraction and reflection. The SNAP protocol also does not require a coordinator—a potential single point of failure—like ZigBee.”
Wireless RF lighting control may supplement hardwired lighting control systems or be required to join with building automation systems. For example, in an existing room with two entries, if putting a switch at the second entry is cost-prohibitive, another solution might be to install a three-way RF wireless line-voltage switch with an additional wireless switch.
Wherever integration is required between hardwired and wireless systems with different protocols, it is important to verify that the given systems support information sharing or, otherwise, that a gateway can be installed to accomplish this.
In closing, John Elzie, product manager for dimming and RF controls for Leviton, said, “Take ownership of the project at hand, and take the time to understand the basics of applying radio frequency products into a facility. Be the best contractor there is by understanding the implications of radio frequency design, building materials and placement of devices, technology pros and cons. The knowledge gap ... between technology advancements and contractor know-how is a great opportunity for contractors to excel and generate huge return on investment.”