Specifying lighting controls: Part 2
When specifying a lighting control system, reviewing the four types of lighting control discussed in part 1 of this series is a good place to start. Part 2 tells you how to determine what kind of lighting control system meets the client's requirements.
To start determining what kind of lighting control system meets your client's or project's needs, make a list of the requirements. This can be a pretty daunting task; consider that the U.S. Dept. of Energy's Building Technology Department's Lighting Development, Application, and Compliance Guide has 15 pages dedicated to lighting control and doesn't even come close to covering all the different scenarios that require lighting control. But there are some fairly basic considerations that are common to most projects: location, occupant schedule, building use, control, size, energy performance, cost, and commissioning.
Where the project is located will have an impact on the extent and possibly the type of lighting controls. As of July 1, 2014, title 24 part 6 of California's Building Energy Efficiency Program requires mandatory lighting control for newly constructed or altered buildings. In addition to lighting control, title 24 part 6 also requires control of plug loads, demand response loads, sign lighting, and energy metering, and commissioning of the facility and the associated control systems. Almost any type of lighting control can be used to satisfy this basic requirement.
Occupant schedule: An office building has different requirements for lighting control compared to a data center. Office buildings are typically on a five-day schedule with a fairly predictable occupant load. On the other hand, a data center may have no lighting or only minimum lighting levels for the majority of time, aside from preplanned service or inspection appointments and unplanned service that require high and consistent lighting levels to identify and work on the IT equipment. With this in mind, an addressable or modular dimming control system with motion or sound control is the best choice of lighting control for data centers and other buildings alike.
Building use: The proper type of lighting control system for the project is directly correlated to how the building will be used. Is it an office building or a data center? Is task, display, or accent lighting required? Are low levels of light acceptable in some places and high levels required in others? TIA-942-A, Telecommunications Infrastructure Requirements for Data Centers, specifies light levels for data centers according to low, medium, and high light levels. Low allows for surveillance, medium allows for movement, and high is best for servicing and installing IT equipment. Ambient lighting typically addresses the low and medium levels, while the high levels may use task lighting, which is often implemented using sensors for a "follow-me" system. Office building lighting levels are suggested by the IES Lighting Handbook, which includes considerations not found in data center lighting, such as occupancy loads, accent lighting, and daylighting. A mix of addressable or modular lighting control for locations with variable lighting levels, and relay or panelboard lighting control for decorative areas may be required to achieve the desired result.
Control: You need to determine what kind of control the client wants. Does the client require individual luminaire or zone control? Should the lighting control be accessible in multiple locations or one centralized location? Is automatic or manual control preferred for all or only some of the luminaires? An addressable control system allows for control of individual luminaires; a relay control system only allows for zone control at best. The addressable luminaire systems typically come at a premium and require communications infrastructure and programming, while the relay- or panel-based systems are usually much cheaper to implement. Keep this in mind when choosing the best lighting control system for the project.
Size: Much in the same way that the use of a building helps determine the proper lighting control system to install, the size of a building also affects the lighting that's needed. For instance, a large building may have completely different lighting control requirements than a small building does. While it may be expensive to implement an addressable lighting control system for every luminaire in a large building, the cost to do the same in a smaller system may not be as high, and the desired energy savings may dictate this path.
Energy performance: Sustainable design standards, such as LEED v4, ASHRAE 189.1, Green Globes, and the IgCC, require the lighting system to meet certain power density and control requirements. Ideally, a building built to one of these standards would have every single luminaire individually controlled to optimize lighting energy use, which can be done using an addressable lighting control system. However, this system comes at a premium, as the material and installation costs are higher than most other types of lighting control systems. If you are operating under a constrained budget, it may behoove you to consider lighting systems that are slightly less energy efficient but more cost-effective than an addressable lighting control system. For more details on lighting controls and energy performance, see this article.
Cost: This important factor has been touched on throughout the above considerations, as a project's budget can greatly affect the type of lighting system implemented. Whether it is justifying the higher cost of the system by demonstrating how quickly the system will pay for itself through its lower operational costs (payback) or justifying increased cost to meet the power density required, cost should always be a factor. Keep in mind that less complex systems that are relay or panelboard based are significantly cheaper than addressable or modular systems.
Commissioning: You should note that the type and size of the lighting control system will drive commissioning requirements and the commissioning process. All types of lighting control used to meet sustainable design requirements-and most building code requirements-likely need to be commissioned. During design development, you should define the commissioning and testing requirements, interface with other systems or devices, and coordinate with the commissioning authority. For example, an addressable control lighting system with its multiple components, control interfaces, and wiring will require more effort on part of the commissioning authority than a panelboard system.
While this wasn't an all-inclusive look at the factors involved in choosing a lighting control, hopefully it gave you an idea of some of the considerations to keep in mind when choosing a lighting control system.
Michael Heinsdorf, PE, LEED AP, CDT is an engineering specification writer at ARCOM MasterSpec. He has more than 10 years of experience in consulting engineering, and is the lead author of MasterSpec Electrical, Communications, and Electronic Safety and Security guide specifications. He holds a BSEE from Drexel University and is currently pursuing a master's in engineering at Drexel University.