Consulting-Specifying Engineer - February 2009 - (Page 25)

Controlling interior lighting (and the law) Since the adoption of the International Building Code (IBC) and its reference to the International Energy Conservation Code (IECC), there has been an ever-increasing interest in the engineering design community in automatic shutoff control of lighting. Specifically, the IECC now requires that every space in a building have either occupancy controls or a timer-controlled lighting contactor, multi-pole relays, or low-voltage relays so that all lights may be turned off during unoccupied periods of the day. In lieu of a simple timer, there is a wide range of more sophisticated, centralized control systems that can be dedicated to lighting control with a wide variety of programming options. In addition, many of the BAS have interface units that enable them to not only control heating and cooling in the building, but also provide lighting control as sophisticated as the stand-alone lighting control systems. While most jurisdictions that have adopted the IBC, many also have adopted the IECC, making the lighting control requirements enforceable by the local authority having jurisdiction (AHJ). However, a few jurisdictions (such as Pennsylvania, which will be used as an example in this article) have adopted the IECC requirements as an enforceable law, upgrading its status from merely a code. This change allows the authority to make changes and allow adjustments out of the jurisdiction of the AHJ, and the lighting control requirement enforceable by law (and, although not addressed in this article, the associated lighting wattage power densities as well). While the actual enforcement authority and potential penalties seem to be relatively obscure, the potential for monetary fines and imprisonment should make adhering to the IECC requirements much less arbitrary for the design engineers than if the same requirements were only a code. Lighting control options The available options for occupancysensor controls (OC) for office lighting are quite varied and can provide a wide range of flexibility as to coverage and sensor types, with each option allowing precise tailoring of control to fit the areas to be covered The available options for occupancy sensor controls for office lighting are quite varied and can provide a wide range of flexibility as to coverage, sensor types, etc., with each option allowing precise tailoring of control to fit the areas to be covered and the types of activities in those areas. Photo: Leviton and the types of activities in those areas. As outlined above, the options for control of office lighting using contactors and some type of control system are relatively straightforward; further exploration of the specifics may be discussed with the manufacturer’s representative of the individual systems. The simplest OC for retrofit applications is the wall-box mounted sensor, which replaces the light switch that controls the lights in that room. Each unit comes with a lensed sensor to provide the coverage range that is required by the application. Most of these units also have an integral override switch to turn the lights off, no matter what motion is sensed in the area, and a timer that allows an adjustable time between the last detection of occupation or motion in the area and shut-down of the lighting in the area. Three general types of sensor technologies are used in these wall-box sensors, each with its own advantages and/or disadvantages: ultrasonic, passive infrared, and combination technology. The ultrasonic sensing element provides the most complete coverage of an area, but it has the disadvantage of no clear cutoff for the coverage. Therefore, it is possible for people or moving objects in an area adjacent to the control zone to trigger the sensor while there is actually no one in the covered area. The passive infrared sensing element eliminates the false lighting activation because it has a precise area of coverage that may be adjusted by blocking off sectors of the sensor to adjust the angle of coverage. However, because of this precise coverage, personnel movement or presence behind stationary objects cannot be detected, so low partitions or large objects in the covered area can prevent the sensor from staying energized when its beam cannot “view” the occupants directly. If there are multiple zones that require different schedules, the use of a central, programmable lighting controller can provide the needed flexibility and minimize the installation complexity. Photo: Square D Consulting-Specifying Engineer • FEBRUARY 2009 25

Table of Contents Feed for the Digital Edition of Consulting-Specifying Engineer - February 2009

Consulting-Specifying Engineer - February 2009 Contents Viewpoint News M/E Roundtable Codes & Standards Electrical Modernization: A Tale of Two Hospitals Retrofitting Office Lighting Controls Case Study New Products Equipment Lifecycles Advertiser Index Green Space

Consulting-Specifying Engineer - February 2009

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