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Article - June 2003
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EMAIL INTERVIEW David Peterson & Ken Sinclair

A lighting controls professional for more than 25 years, David Peterson serves as Chairman of the Joint Sections Committee on DALI for the National Electrical Manufacturers Association (NEMA). He is the Director of Strategic Marketing for The Watt Stopper, Inc., a lighting controls manufacturer.

www.wattstopper.com


Sinclair:  What is DALI and why should the facility management professional care? It seems to me that a lot of building management professionals have a vague understanding of what DALI is, and that this is some new type of building management technology like BACnet or Echelon.

Peterson:  That's a good point, Ken. DALI stands for Digital Addressable Lighting Interface, and as a tool for lighting systems, it has a great deal of potential. What it's not is another type of building management system protocol. In many respects DALI is like BACnet and Echelon because it is a communications protocol. It differs from these other protocol standards because it is very application-specific, having been designed and standardized to work with lighting ballasts. DALI's importance is that we now have a medium through which we can communicate with and control each and every individual ballast independently. BACnet and Echelons are more encompassing protocols, designed to allow multiple, application-specific systems to communicate and work together in a building-wide control system. DALI's scope defines how to communicate to and from a DALI ballast and how the ballast will respond when it receives a DALI command.

That said, DALI enables lighting control in ways that have never been available before. We're talking about lighting control down to the individual ballast level, control that's achieved by how you communicate to the ballast rather than by how you wire to the ballast. This control can be repeatedly reprogrammed to meet changing workplace needs, and it opens up a whole universe of control possibilities. Lighting control and dimming that used to be accomplished by how ballasts and light fixtures were "hardwired" during electrical construction can now be free of these constraints. We no longer need to plan how to wire the fixtures; rather, we can focus on how we want them grouped, zoned or controlled after the wiring is installed. Then, if a need arises to change the grouping or zoning at a future time, the system can be reprogrammed, instead of re-wired, to accommodate the new desired control.

By enabling ON/OFF or dimming control down to the individual ballast level, DALI offers a tremendous amount of flexibility both in control capability and in utilizing building space. Building managers should care because DALI gives them the ability to meet a number of important goals more effectively: increased flexibility in building operations, reduced installation costs, and a greater ability to control lighting that provides a productive and comfortable environment for occupants.

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Sinclair:  Dave, why do you think building professionals will choose DALI?

Peterson:  The motivations will depend on the role of the professional, Ken. For instance, a building owner will be attracted by the reduced costs; reconfiguring a space will be far less costly using DALI. This is an important consideration, when you realize that the average office space is leased for only seven years. Tenants and users will value the flexibility a DALI system can give them in accommodating their specific needs. Engineers will also find the flexibility DALI gives them is an asset. And all of these professionals will recognize the importance of a system that can provide these benefits along with the added potential of more effective energy management.

Sinclair:  Is DALI available for all types of lighting components?

Peterson:  Currently, DALI ballasts are available for the most common fluorescent lamp types: T8, T5 and T5HO linear fluorescents, compact fluorescents and biax. Some manufacturers are expected to roll out DALI-compatible dimmers for halogen and incandescent lighting this year, while other types of lighting such as high-intensity discharge are a little further away in terms of product availability.

Sinclair:  How is this new approach different from current control technologies, such as 0-10V systems?

Peterson:  First, DALI is based on digital, 2-way communications. This means that a facility manager can give an individual ballast specific commands, such as to change to a specific output level, to change levels at a specified rate (fade), or to operate at a maximum output level. These commands as well as the lighting output for each level are consistent from one manufacturer to the next, allowing users to install ballasts from different manufacturers side-by-side. By contrast, a 0-10V system can only command a single ballast or group of ballasts to change output levels based on the control voltage depending on how the ballasts were initially wired. Ballasts from different suppliers may have very different responses. And DALI's two-way communication means that information such as lamp failures or energy use can be supplied to a central PC.

Second, facility managers can address each DALI ballast, allowing control down to an individual fixture over a single 2-wire data bus. This makes it practical, for example, to provide individual occupant control in an open office application. Doing so with a 0-10v system would require a home run of the low voltage cable for each occupant.

Sinclair:  Describe what a typical DALI-compatible system entails.

Peterson:  Up to now, it would include DALI-compatible ballasts in each fixture, a power supply for up to 64 DALI ballasts, communications wiring to all ballasts, power supply, and switches or associated controls (this 2-wire communication bus among the ballasts and other components is referred to as a "loop"), and a communications link to a central PC for programming and control. The latter can be a centralized, computer-based system for facility-wide control or even local PCs for individual occupant control. Commissioning such a system requires that users address and identify each ballast on the facility's floor plan before programming the intended operation.

New, stand-alone DALI control products are emerging in the marketplace that provide the ability to control lighting groups, create user scenes, and integrate automatic shutoff without the need for PC-based central controls or special programming tools. In this case, the system would include the DALI ballasts, a power supply, wiring, and a wall box dimmer/controller. An electrical contractor can install and commission the complete system.

Reliable ControlsSinclair:  Is DALI a broadly applicable solution? I guess what I mean by that is are there some applications that are better suited to DALI-based control than others?

Peterson:  Every type of lighting control technology and product has optimal applications as well as ones where the result is less ideal. With that in mind, I would say that the greatest potential for DALI is in those spaces with multiple uses and areas where lighting levels and configurations are likely to change over time. Conference rooms, classrooms, and lecture rooms are good examples. Each can take advantage of DALI's flexibility and multiple scene control. Using a stand-alone wall-box controller in a lecture hall, for instance, a speaker can push a 100% scene button. For an A/V presentation, the same lecturer can push the "A/V" scene button and the lighting will fade to a lower level, with some fixtures completely off and some at a lower output so students can still see enough to take notes. The reduced cost of installation as well as the simplicity of DALI may make dimming control particularly appealing for smaller conference and meeting rooms and private offices, where it might not otherwise be considered.

There are also some broad functions that DALI is especially well suited for, such as demand reduction, load shedding, and daylighting. I think we can anticipate that these may become important applications for DALI-compatible products in the future especially as their capabilities are further developed and enhanced. As you know, Ken, time-of-use and real-time pricing energy rates are expected to become much more widespread in the years to come, and under these types of pricing structures, managing demand and minimizing demand charges becomes even more vital to effective energy management. By the same token, load shedding may become even more critical in some areas of the country, as we have seen in recent years. For both purposes, DALI gives building managers the capability to reduce selected lighting loads gradually over several minutes to avoid occupant distraction. For instance, in an office building, a facility manager could assign lighting in hallways to a "shed" group, dimming it to 50% when needed or desired while still maintaining an adequate lighting level for occupant traffic. Or in open office areas, the same type of grouping could be done without losing any uniformity of lighting level throughout the space. In fact, DALI control is a very effective method to achieve bi-level switching, which is mandatory in some jurisdictions' energy codes.

Finally, in the area of daylighting, DALI offers the ability to truly integrate lighting fixture by fixture with daylighting controls to achieve a pleasing lighting distribution throughout the space. Up to now, this has been a very difficult result to achieve because it requires programming the response of specific fixtures depending on their location within a space relative to the daylight source while also providing for the unique needs of each occupant. DALI technology will make this customized control practical, as DALI-compatible daylighting control devices continue to be developed in this realm. We can anticipate that this capability will become available in the future.

Sinclair:  I know DALI has been in use in Europe for a few years now. How is the development of this standard evolving in the United States? What are some of the ongoing efforts?

Peterson:  Here in the U.S., the National Electrical Manufacturers Association (NEMA) is taking the lead in developing a DALI controls standard to insure that controls from different manufacturers are compatible and that the controls and ballasts function as a system. This requires agreement on basic functionality, wiring practices, electrical characteristics and expanded command sets. This is a major undertaking but a critical step for DALI to go mainstream. The California Energy Commission (CEC) is also playing an important role. Through a project under the auspices of its PIER (Public Interest Energy Research) program, the CEC is playing an active role in the commercialization of the DALI technology by conducting important needs and technology assessments, supporting the development of a draft standard, and demonstrating its application. Ultimately, the CEC efforts will help make lighting a controllable load.

Sinclair:  Tell me, Dave, in the near term, how do you envision DALI acceptance in the marketplace?

Peterson:  I really see two different but parallel avenues of acceptance. The first avenue involves what I call "full-scale" DALI implementation. This occurs in settings where there is a large complex with a high level of sophistication on the owner's part. In this type of setting, the lighting systems involve integration with the facility's building management system. For these types of applications, what I call "full-scale" DALI capabilities are ideal, providing interfaces with the BAS, local PC-based control capabilities for occupants, and the like. While there may not be thousands or even hundreds of these types of settings, they do account for a significant amount of the total square footage of commercial space nationally. The "test-bed" types of demonstrations we often see that are designed to validate the technology on the largest scale will be undertaken in these types of settings. In fact, there are already a number of these large demonstrations underway. For instance, the architectural and design firm Hellmuth, Obata + Kassabaum Inc. (HOK) incorporated DALI into its lighting system at its new offices in San Francisco.

The second avenue involves the use of stand-alone DALI controls. This occurs in smaller facilities or individual space settings that can benefit from the use of DALI-based controls, but that may not have the need for facility-wide, centralized control. For these types of applications, the stand-alone DALI control products can provide effective control while being easy to install, commission and operate. We're seeing a number of manufacturers introducing these stand-alone DALI controls, some using wall switches with push-button programming. This type of control offers the opportunity to try out DALI technology on a much smaller scale while still providing the scalability for the future. I think the marketplace acceptance of DALI will begin from these two approaches. As we learn more and further refine the product offerings that take advantage of DALI, we'll begin to see a broader, more pervasive acceptance.


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