Personal Dimming Controls

Preferences for lighting levels vary widely in commercial buildings. Workers who use computer display terminals typically prefer relatively low lighting levels to minimize glare and reflections on their display screens. On the other hand, workers who read, write, and draw on paper typically prefer relatively high lighting levels so they can see small letters and fine details. Older workers, and others with weak vision, also need higher lighting levels. The ability to adjust lighting levels is especially important for workers seated near windows, who must adapt to varying levels of sunlight during the day, and workers who require different lighting levels for the different daily tasks that they perform.

Until recently, it was impractical to provide different lighting levels for different workers, except by using task lighting. In recent years, technological advances have produced personal dimming systems that make it feasible for individual workers to control lighting levels in their personal workspaces. These systems offer the potential to save energy through their dimming capabilities and to reduce electrical demand during peak hours. However, they will rarely pay for themselves on that basis alone. Instead, most companies justify them based on the dimming systems' effect on employee morale and performance.

What are the options?
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Control location. Lighting controls can be placed at the door, as are standard switches, or at the worker's desktop. A study conducted by the Lighting Research Center showed strong worker preference for the desktop location.

Controls with memory. The same study showed that workers who had to manually reset their preferred light level each time they turned on the lights were less likely to dim their lights than workers whose controls at start-up automatically returned lights to the preferred level.

Ballast flexibility. Dimming systems may come with ballasts included; they may be compatible with a specific ballast, or they may work with any ballast having a 0- to 10-volt control signal.

Handheld controls. At least two companies offer personal dimming systems with handheld wireless, infrared (IR) remote controllers, similar to the remotes that control TVs and VCRs in the home (Figure 1). The units enable fixtures to be controlled individually or in groups connected by low-voltage wiring. Most building codes allow low-voltage wiring to run above a suspended ceiling without conduit.

Figure 1: System for dimming lights with handheld infrared controller
This system enables users to dim lights with handheld wireless remote controllers similar to the remotes that control TVs and VCRs.

Direct-wired controls. Direct-wired controllers are also available. These devices use a small amount of power from the ballasts for remote control, so no batteries are required. In addition, the controllers do not depend on line of sight, as do IR controllers, making them easier for users to operate. Wiring is either free-run through the walls or colocated with communications wiring.

Desktop computer controls. At least one manufacturer offers a system through which users can control lighting levels via their personal computers (PCs). Each fixture is assigned an identification number and is linked to a local area network. Selected users, such as energy managers, can control all the fixtures from a PC for systemwide monitoring or energy savings programs.

How to make the best choice
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Evaluate the desirability of personal dimming control. The productivity and morale benefits of personal dimming control are hard to quantify, but they're also hard to ignore. The clearest case for personal dimming can be made in cases where conflicts between lighting system user groups are obviously interfering with individuals' work. For example, one company faced considerable worker dissatisfaction when it relocated its computer-aided design (CAD) operators from their own, self-contained area into the space occupied by its engineering project teams. CAD operators complained about glare on their computer screens from bright overhead lights, while engineers, who worked mostly on paper tasks, demanded high light levels. The installation of personal dimming systems resolved the conflict.

Consider products with multilevel addressing capabilities. With multilevel addressing, a dimming system can be used to control individual fixtures as well as zones or departments. That capability enables an individual manager to control lights to limit peak loads at certain times of day or to schedule systemwide, areawide, or user-specific dimming or shutdowns.

Compare the cost-effectiveness of dimming alternatives. Personal dimming systems can be compared to nondimming systems based on first cost and operating cost differences. Use the calculator below to estimate the payback, based on energy savings, of a personal dimming system. In making the final decision, remember that workers' salaries in a typical office building are nearly 300 times greater than the annual lighting bill, so even tiny improvements in productivity would likely exceed any energy savings.

Cost-effectiveness calculator

What’s on the horizon?
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Look for more manufacturers to provide addressable ballasts that can be linked to local area networks and controlled via PCs. One new product allows individual fixtures to be addressed and controlled remotely with an infrared controller. Up to 100 ballasts can be installed on a circuit, with preset dimming levels and fade times. A growing number of manufacturers are also supporting the Digital Addressable Lighting Interface—a nonproprietary standard that defines interfaces for digital communication among the components of a lighting system.

Who are the manufacturers?
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The following manufacturers offer personal dimming systems.

Neither this list nor any mention of a specific vendor or product constitutes an endorsement or recommendation by E Source, nor does any content the Business Energy Advisor constitute an endorsement or recommendation, explicit or otherwise, of your service provider’s various technology-related programs.
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