Until the mid-1970s, buildings usually were designed without any type of lighting control. In fact, many also were designed without heating systems, because of the enormous heat produced by 24-hour operation of indoor lighting systems. In hot climates, you can imagine how this added to the amount of air conditioning required to cool an entire facility. No wonder that since the first energy codes were implemented in 1975, switches for every room is a basic requirement.
Even if you're designing superefficient buildings, you still have to provide lighting. Normally, efficient lighting with simple switching will consume 20 percent to 40 percent of the total electric energy use of the building, with most of it “on peak” when electricity is most expensive. With the best lamps and ballasts, a superefficient design can save a few more watts. But to significantly reduce lighting use, especially on peak, using state-of-the-art lighting controls is probably the most effective way.
The overarching concept of state-of-the-art lighting controls is to offset the cost of high-performance controls by reducing the cost of equipment and wiring, including copper and steel, as well as the labor that normally is associated with lighting control systems. State-of-the-art systems have the following distinctions:
Contemporary light sources used in commercial lighting such as LED and fluorescent adapt to digital controls easily. Simple additions to ballast or driver internal electronic circuits permit a wide range of control options including on/off switching, dimming, and digital communications. Then “brains” are added so ballasts and drivers can remember their current state and perform complex functions such as individual addressing, programmed response, and the ability to communicate with a central control panel or building management system.
An alternate smart system takes the brains out of the ballasts and puts them in zone controllers. Zone controllers are a useful hybrid; they perform almost all of the duties of a smart ballast, but one controller can drive a large number of conventional lamps and ballasts that all switch and dim at the same time and by the same amount.
What makes this possible is the low cost of embedded controllers with memory. In the case of a fluorescent ballast, the added cost of brains and dimming should be only $25 to $30 more than a nondimming dumb ballast. The minuscule demand for these types of controllers has kept this price from becoming a reality, but that is changing.
STATE-OF-THE-ART COMMERCIAL LIGHTING CONTROL OPTIONS There are three different approaches to commercial control systems.
Digital Addressable Lighting Interface (DALI)–based systems are simple to the point of elegance. A complete DALI system consists of a bus hub and sensors, ballasts, and input ports connected on a simple two-wire bus circuit. Programming is stored throughout the circuit's devices. Although DALI buses are limited to 64 nodes per bus, multiple buses can be used. A master “overlay” computer can be added that interconnects buses and enables interbus communication and powerful functionality. There also are systems, such as Lutron's Ecosystem, that essentially are DALI-based but not advertised as such.
Zone-based systems are hardware intensive and require a master overlay computer. For each zone or small group of zones there is a zone controller to which the loads, sensors, and input ports are hardwired. Systems include a controller for every zone and a digital network (usually Ethernet). The master overlay computer connects to and communicates with all of the zone controllers. Zone controllers can switch any lamp load and dim 10-volt analog ballasts and drivers.
Legacy-based systems are hardware and wiring intensive. Because they are based around old-fashioned relay and dimmer panel design, these systems are only marginally described as state-of-the-art. But they can offer the best of the old along with some of the new, giving designers the most options, including DALI. Because these systems were developed for networking amid relay and dimming cabinets, powerful overlay computer controls are standard.