Figure 6-15. - Luminaire utilization.

Normally, each luminaire manufacturer can supply you with the maintenance factor for your lamp model; however, when the manufacturer's information is not available, a 0.70 maintenance factor is widely used in the industry.

LIGHTING INTENSITY CALCULATIONS

Achieving the most satisfactory solution for any given lighting problem requires sound judgment in making necessary compromises of all factors involved.

Selection of the luminaire can be influenced by budget constraints, present stock levels in the Federal Supply System, and availability. Once the luminaire is selected, it is important that you use the manufacturer's literature to determine the number of luminaries, mounting height, and spacing required to produce the desired illumination intensity.

Using the manufacturer's literature supplied in figure 6-14, let us solve this sample problem: Find:

1. One-sided spacing required to provide specified illumination

2. Uniformity of illumination

Given: (fig. 6-16)

Street width, 50 feet

Mounting height, 40 feet

Pole setback from curb, 2 feet

Figure 6-16. - Streetlight sample problem.