Project managers for electrical contracting firms often think in terms of hours — not dollars — when considering the scope of a job. Anything that can help them cut corners without sacrificing performance, quality, or safety gets their attention. In the field of commercial lighting control systems, the emerging industry standard for both new construction and retrofits calls for versatility and “out-of-the-box” integration. The former allows for a system to be customized for each particular project; the latter enables a contractor to complete the job fast.
As lighting control systems grow in sophistication, and as building codes become more stringent, the motivation for specifiers to choose even more selectively is only becoming stronger. The most advanced lighting systems now employ various technologies, such as daylight sensing, occupant sensing, dimming, and personal control. The integration of these features gives building owners/managers unprecedented capabilities to design, configure, reconfigure, and maintain lighting systems more easily, realizing significant energy-usage savings at the same time.
One breakthrough in this area is the digital addressability of the components, including ballasts. It is now possible for any combination of sensors or wall controls to be connected to a lighting control system's ballasts. Because there is no need for interfaces or power packs, sensors and wall stations can be removed or added with simple Class 2 connections at any fixture. Maintenance is greatly simplified as replacement ballasts and bus supplies instantly “learn” their programming when they first communicate with already installed devices. System settings and individual device information are stored redundantly. The ballasts back up the power supply programming, and the power supply backs up the ballasts' information.
Every ballast is uniquely identified by a serial number which makes replacing devices as simple as entering two numbers into a handheld programmer — the serial number of the unit being replaced and the serial number of the new unit. Once entered, the new unit fully functions in the system. This approach eliminates the need for readdressing and reprogramming.
The structure and versatility of a system can remain intact as it grows from one ballast to several. A single lighting control network allows users to connect up to 64 ballasts and a power supply with a simple 2-wire communication wire. Larger systems are constructed by connecting multiple 64-ballast loops. Within this lighting control network, any sensor or wall station can speak to any or all of the other ballasts on the loop.
Such systems provide installers with control wiring options that satisfy customized installations. The control wiring can be either Class 1, which runs in conduit with the power wiring, or Class 2, which is wired in a cable tray or with other communication wiring. Modular cable can be used to quickly connect fixtures and drastically reduce overall wiring time in new construction. If desired, the control wiring also can be wired as Class 2 in cable tray or with other communication wiring (ideal for retrofit applications).
In addition, installers can select their preferred wiring format, such as daisy chain, star, or T-tap, because the control wiring is topology-free. It's also polarity-free. If the control wiring is reversed when connected, the ballast will still operate. Whether the control wiring is Class 1 or Class 2, the sensors and wall stations are easily added or removed with simple Class 2 connections at any fixture. Free from interfaces and power packs, there are fewer parts and pieces required for installation.
Making a difference
After recently installing a lighting control system in one of the newest high-rise office towers in Philadelphia, Bob Steinberg, a project manager for Hatzel & Buehler, Inc., Wilmington, Del., says energy savings is the sales pitch that gets a lighting system in the door. “But for guys like us, it's the ease of these jobs that we notice,” he says. “Something that used to be time-consuming is now done quickly and simply.”
Based on Steinberg's experience, he says building owners and tenants mention two primary reasons in choosing a lighting system: energy savings and flexibility. Lighting accounts for about 45% of an office building's energy consumption, according to the U.S. Energy Information Administration. It increases to 56% for educational facilities. Any lighting control system that can reduce the monthly electric bill and, at the same time, accommodate the shifting needs of building tenants represents a dynamic resource for corporate America. The flexibility is vital because office environments today undergo continual transformations. For example, the International Facility Management Association estimates that 44% of office spaces change each year.
It wasn't so long ago that everyone in a given office worked under the same lighting conditions; the lights were “on” and set at the brightest level. Now, advanced lighting control systems enable precise control of one's personal workspace to building-wide control. Lighting scheme changes within rooms, floors, or an entire building are accomplished with a programming menu and without rewiring. With a family of devices that are all addressable right out of the box — sensing environmental changes, sensing presence, programmed for time-of-day and day-of-week usage — the newest integrated digitally addressable systems provide adaptability and light on demand only.
New integrated digital lighting facility management software extends the concept of flexibility by allowing control of lighting from a PC. The software tool reduces downtime and eliminates rewiring costs during reconfiguration by allowing facility maintenance personnel to reassign lighting fixtures and shades to match furniture layouts with the touch of a button. When repurposing a building space — such as when a larger room is split into two — no conduit changes are required. Lighting levels can be changed easily to match the needs of a new client or department.
When designing a lighting system, ballast selection is the first priority. The ballast serves as the centerpiece of the network. The designer should determine the number of fixtures that will be interconnected. Consideration of control zones is not necessary because they can be programmed rather than wired. Another factor in the selection of a ballast is the range of dimming capability desired: 100% to 10% or, in some cases, down to 1%.
Sensor selection has its own design considerations. For example, one daylight sensor should be earmarked for each 30-foot zone of fenestration. As now equipped, wiring a daylight sensor to one ballast allows control of multiple ballasts on the bus. The digital ballast accepts only one IR input, so use of the IR input for the daylight sensor precludes the use of an infrared receiver with the same ballast.
Placement of the daylight sensor must take the following into account:
The sensor should have an arrow on it indicating its orientation.
The sensor should be mounted so its viewing area is centered upon the nearest window at a distance of between one to two times the effective window height (the height of the window, starting at the window sill or at 3 feet from the floor, whichever is greater).
The daylight sensor's view should have no obstruction.
The sensor should not be positioned in the well of a skylight or above indirect lighting fixtures.
Occupancy sensors come in three classes: ultrasonic, infrared, and dual-tech. Ultrasonic sensors are designed for small movement detection when fans or other automated systems are not present. Infrared sensors are ideal for occupant detection when “line of sight” is available from the sensor. Dual sensors combine both technologies for applicable situations.
Controls for the most advanced lighting control systems include personal control devices, infrared receivers, and wallstations. When mounting an infrared receiver, keep in mind that their cone of reception can be diminished when positioned less than 10 feet from the floor.
The bus supply, which is required for two or more ballasts to work together, powers the communication bus, can support as many as 64 ballasts, and can be integrated with multiple other bus supplies or different lighting control systems. The wiring to these bus supplies is interesting. The bus supply does not have to be located at the end of the bus. The E1 and E2 wires connecting the ballast terminals with the bus supply are polarity insensitive, and, regardless of bus wire gauge, ballast terminals will hold only one No. 16 to No. 18 AWG solid wire. In most cases, a wire connection to the bus is required.
Integration with a building's emergency systems is accomplished in two different ways. If no power is lost, an emergency signal can be sent from a building management system or emergency system to the contact closure on the bus supply. All ballasts on the bus can respond by going to 100%, unless programmed to do otherwise. If normal power is lost, all ballasts can turn off, except those that are fed by the emergency power source (such as a generator or battery). As in the other case, the ballasts receiving emergency power would go to 100%, unless otherwise programmed.
Because electrical contractors are often the point of reference for building owners and managers for lighting systems, it is essential that they stay up to speed with latest technologies and capabilities in this market.
Lind is a director for Lutron Electronics in Coopersburg, Pa.