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INTRODUCTION

Electric outdoor lights are generally controlled in groups via relays (contactors) and photocells, or controlled individually with photocells mounted on the luminaires. In some cases time clocks are used to control the lighting. Today's digital technology, in both control systems and light sources, offers new potential to better control the lighting system and provide the right amount of lighting when required. These improved controls allow the lighting system to adapt the lighting levels to the ambient conditions. Better lighting controls can result in improved visibility and potential savings in both energy and maintenance costs. The purpose of this Design Guide is to educate the reader on control technologies, and to advise considerations for their implementation.

Before moving forward, it should be understood that these new systems, while bringing the potential to improve visibility as well as considerably reduce both energy and maintenance costs, also bring a significant and long-term investment. For that reason, the user/designer should understand the functionalities and consequences of the different technologies, each with its own cost/benefit analysis.

The drive to reduce energy consumption, and the related costs, has led to new strategies for lighting controls. In many cases, particularly in retail areas and parking lots, full light output is not required throughout the duration of the night, after business hours. In some cases street and roadway lighting can also be reduced as the level of activity is reduced, at specific times during the hours of darkness. New digital technologies in both controls and light sources now enable the user to turn specific individual or groups of lights on or off, or to adjust individual or group light levels up or down as needed. These new control systems enable full customization - from individual light points to complete lighting systems - in order to meet the specific needs of each user. Adaptive control systems can make adjustments due to changing ambient light levels, pedestrian activity, vehicular traffic and even weather conditions.

This Design Guide presents an overview of lighting control technologies, some of which are new and evolving, and others which have a proven history (for examples, refer to IES TM-23-11 Lighting Control Protocols).