Page 145 - Pipeline Rules of Thumb Handbook

132 Pipeline Rules of Thumb Handbook

Table 2 Table 3
Outdoor Floodlight Luminaire Designations Typical CBU’s

Beam Spread, Degrees NEMA Type Area CBU Area fc

10 up to 18 1 Baseball
>18 up to 29 2 Infield 0.65 Tennis 0.75
>29 up to 46 3 Outfield 0.85 Large parking lots 0.80
>46 up to 70 4 Football 0.60 Building facades 0.65
>70 up to 100 5
>100 up to 130 6
As an approximation, the average CBU of all the floodlights
>130 up 7
in an installation should fall within the range of 0.6 to 0.9. If
less than 60% of the beam lumens are utilized, a more eco-
The following general principles apply in the choice of beam spread:
1. The greater the distance from the floodlight to the area to be lighted, nomical lighting plan should be possible by using different
the narrower the beam spread desired. locations or narrower beam floodlights. If the CBU is over
2. Since by definition the candlepower at the edge of a floodlight beam 0.9, it is probable that the beam spread selected is too narrow
is 10% of the candlepower near the center of the beam, the illumi- and the resultant illumination will be spotty. An estimated
nation level at the edge of the beam is one-tenth or less of that at
the center. To obtain reasonable uniformity of illumination the beams CBU can be determined by experience, or by making calcu-
of individual floodlights must overlap each other as well as the edge lations for several potential aiming points and using the
of the surface to be lighted. average figure thus obtained.
3. The percentage of beam lumens falling outside the area to be lighted Step 4—Determine the quantity of floodlights (N)
is usually lower with narrow-beam units than with wide-beam units. required. Rearrange the basic formula in Step 1 as follows:
Thus narrow-beam floodlights are preferable where they will provide
the necessary degree of uniformity of illumination and the proper
footcandle level. A ¥ fc
N = (5)
¥
BL ¥ CBU LLF

Conductor size conversion chart—Metric to AWG

Table 4

Metric Size AWG Size

2.5mm 2 #14
4mm 2 #12
6mm 2 #10
10mm 2 #8
16mm 2 #6
25mm 2 #3 1
35mm 2 #2
35mm 2 #1 1
50mm 2 #1/0
70mm 2 #2/0
95mm 2 #3/0
95mm 2 #4/0 1
120mm 2 250kcmil
150mm 2 300kcmil
185mm 2 350kcmil 1
185mm 2 400kcmil 1
240mm 2 500kcmil
300mm 2 600kcmil
400mm 2 700kcmil
400mm 2 750kcmil
400mm 2 800kcmil 1
1 This AWG size is the closest equivalent to the metric size.