Most commercial building energy codes require that exterior lighting be turned OFF when not in use via a time- or daylight-based control. Now a growing number of codes based on ASHRAE/IES 90.1-2010 require that exterior luminaires that remain on after normal business hours, must have the lighting power reduced during that time.
The approach basically requires that lighting power be reduced automatically during a certain time of night, and that light and power subsequently be raised and lowered based on whether the lighted area is occupied. This involves using an occupancy sensor that changes the lighting state from a low (typically 30- to 70% of rated power, but can be even lower) to a high setting. The approach is compatible with any light source having typical use in exterior lighting applications.
Simple and straight forward, bi-level dimming control offers the ability to dim luminaires when little to no traffic on the lot is expected. Using a time clock or other device to establish pre-determined dim periods, bi-level dimming allows significant energy savings to be realized while still providing lot-wide illumination for security purposes.
Read full article online: http://inews.acuitybrandscontrols.com/