Consulting-Specifying Engineer - November 2008 - (Page 26)

Fluorescent, LED, and low voltage lighting in the reception area, kitchen, and a conference room were integrated by The Lighting Practice for their offices in Philadelphia. Photo: Watt Stopper/Legrand Daylighting controls According to a recent study by The Heschong Mahone Group and Southern California Edison, daylight responsive controls require commissioning to meet their energy predictions3. The study highlighted the need for user controls, as-built documentation, and owner training. Commissioning activities for three types of daylight responsive controls are described here. The simplest automated daylight responsive controls turn lights OFF when the daylight levels rise above a minimum threshold. An override switch and some adjustment of the OFF threshold are required to head off combative and annoyed occupants. These should be sufficiently labeled for current and future occupants. A marker, arrow, or other indication of the ON and the OFF threshold should be indicated as clearly as possible. A quantitative value such as foot-candles is recorded in the as-built/project documents. Designers often choose not to turn lights OFF (in response to daylight) in occupied areas. Either the equipment cannot be installed with an appropriate deadband, or it is likely not to be installed with a deadband, leading to cycling of lights ON and OFF and finally the disabling of the OFF function by the annoyed occupants. It is important to emphasize the differences in design and commissioning. The commissioning authority does not “set up” the system, but instead verifies the setup implemented by the contractor according to the designer’s setpoints and sequence of operation. Administering sufficient deadbands into the design/settings is a byproduct of competent design, which the commission authority can flag if not indicated clearly in the design documents. A high/low (bilevel) or multilevel scheme uses switching to turn a number of lights OFF in response to daylight while maintaining uniform light distribution in the space. This scheme may be controlled through manual switching or use of photocells. The controls may either turn individual lamps OFF or turn OFF every other fixture. As with ON/OFF control, labeling the manual override, user control of threshold, and owner training is crucial. Another sensor control scheme uses continuous dimming, which linearly reduces the light output of the lamp with increasing daylight levels. If the photosensor is integral to the light fixture, each row of lights may be adjusted as you move away from the daylight source. This typically is done at startup, and workspace luminance should be recorded by the commissioning agent and compared with the expected results. Alternatively, in a system where fixtures are networked together, a multiplier can be programmed to adjust multiple rows independently based on the input from one photosensor. Owner training can empower the occupants to properly use control features, make adjustments, and understand exactly how their adjustments affect the light source, enabling them to maximize system effectiveness. Lighting manufactures continue to provide new products and, occasionally, userfriendly controls. Current studies, as well as practical field experience, indicate the need for detailed design, proper installation, timely commissioning, ample documentation, and owner training of lighting control systems in order to meet predicted energy savings. These requirements, when combined with the daunting amount of energy consumed in commercial lighting, and the building industry’s goal to realize widespread energy reductions, ultimately will lead to more requirements for commissioning of lighting systems in new and existing buildings. Hudson works as a technical consultant within a multidiciplinary team of architects, engineers, planners, and building analyst who share extensive hands-on experience in green building. He manages commissioning, retrocommissioning, and energy audits while supporting design simulation for new construction including energy modeling, daylight modeling, and CFD analysis to assess the effectiveness of specific green building strategies. Riley serves as a project manager and lead electrical engineer for George Butler Assocs. commissioning projects. He has been providing electrical systems startup and commissioning services for more than 15 years and has specialized in commissioning critical facilities for the past eight years. He has provided educational presentations for Labs 21, 7x24 Exchange, National Assn. of State Facilitators, and the Data Center Journal. References California Dept. of Energy. 2005. Daylight Controls, Section 5.2.1.4. Oregon Dept. of Energy. Daylighting Controls Factsheet Denniston, S., et al. 2004. “Photocontrols and Daylighting Savings: Urban Myths and Realities from a Field Study.” Proceedings of the Solar Conference, pp. 969-976. 26 Consulting-Specifying Engineer • NOVEMBER 2008

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Consulting-Specifying Engineer - November 2008 Contents Viewpoint News M/E Roundtable Comissioning Lighting Controls Prevent Plugholing: Smoke Control Done Right Commercial Geothermal Heating and Cooling System Design Codes &�Standards Case Study New Products Equipment Lifecycles Advertiser Index Green Space

Consulting-Specifying Engineer - November 2008

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