Outdoor Lighting Selection

The selection process outlined below estimates the number of wide beam floodlights, roadway luminaires, wallighters or high mast lighting systems needed to light an outdoor area from within or from around the perimeter area. The luminaires may be mounted on poles, or on nearby buildings and structures.

For applications lighted from the perimeter, the lighted area is considered to be that bordered by the floodlight locations (even if the luminaires are set back away from the actual application area). This method is only applicable for setbacks of up to one mounting height.

Other considerations are: In general, a luminaire location can effectively cover an area of up to two mounting heights away from it. Floodlights are usually considered first for this because they can be aimed away from their location. For example, this makes them especially suited for lighting from around the perimeter of an area. However, floodlights can only light an area 90 degrees wide, so you usually need two or more units per location. Luminaires with roadway light distribution can cover a wide area both in front of and behind the location, and find application within the site to be lighted. However, roadway luminaires can not light as far out in front as a floodlight. Wallighters are a hybrid luminaire which combines floodlight and roadway characteristics.

A word of caution: This method is not intended for estimating roadway or sports lighting. Here are the steps:

1. Determine the recommended average maintained illumination level in foot-candles.
2. Determine the dimensions (length and width) of the site.
3. Select light source type (high pressure sodium, metal halide, etc.).
4. Use following chart to determine the Watts/Sq. Foot by moving horizontally along the desired footcandle line to the appropriate diagonal light source line and then moving vertically down to read the Watts/Sq. Ft. on the horizontal axis.
5. Calculate the total lamp watts needed for the area:
   Total Watts = Area (L x W) x Watts/Sq. Ft.
   (Multiply all total watts by 1.7 when using Wallighters.)

6. Using your knowledge of the site, determine the probable mounting height for the luminaires. Perhaps the height of a nearby building, existing poles, local height restrictions, nearby lighting or your experience may factor into this decision.

   The simple 2X-4X rule of thumb is also effective. Simply divide the shortest distance that can be covered by adjacent luminaire locations by four to get a mounting height that conforms to the rule. Note that the higher the mounting height, the fewer the locations or poles. Fewer poles, fewer foundations, less wiring, and less trenching translate into lower cost of installation.

7. Using your mounting height, position pole or building mounted luminaire locations. Keep in mind that the luminaire locations should not be spaced more than four mounting heights apart and that light coverage is not effective more than two mounting heights away.
8. Fine tune your layout in terms of quantity of luminaires per location by referring to the guidelines in this section.
9. Now calculate the wattage of the luminaires:

   

10. Select the actual luminaire for your application.

And furthermore . . .

Color Rendering