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What is NEMA?

NEMA is the National Electrical Manufacturers Association which is a trade association of electrical manufacturers founded in 1926. It is an ANSI-accredited organization that develops standards for electrical equipment used in North America, some of which relate to lighting systems.

What is light distribution?

Light distribution can be broadly characterized as narrow, wide, or somewhere in between. Spotlights have a narrow beam, usually less than or equal to 25°. The light is more focused and reaches farther than a wide beam. By contrast, flood lights have a wide beam, usually 45°-120°. The light illuminates a larger area but does not reach as far.

This picture demonstrates different degrees of light distribution.

 

Beam Angles

NEMA beam spread classifications are indicated by a number between 1 and 7 and are broken down in the chart below.

Nema Beam Spread Classifications

Beam Spread Nema Type Beam Description Beam Projection Distance
10° to 18° 1 Very Narrow 240 feet +
18° to 29° 2 Narrow 200 to 240 feet
29° to 46° 3 Medium Narrow 175 to 200 feet
46° to 70° 4 Medium 145 to 175 feet
70° to 100° 5 Medium Wide 105 to 145 feet
100° to 130° 6 Wide 80 to 105 feet
130° + 7 Very Wide < 80 feet

 

As you can see, the wider the beam gets, the shorter the beam projection distance is.

Mounting Height Considerations

To determine the ideal beam angle for a fixture, you need to know the distance between where the light will be mounted and the area to be illuminated. A closer distance means that a wide beam is needed. A further distance means that a narrow beam is needed.

NEMA Pattern Type

Another way that NEMA classifies light distribution is by pattern type. Each of the six types that NEMA identifies are used for different applications. They are illustrated here:

Street Light Optic Patterns

Type I

Pattern type: two-way 15° lateral distribution
Applications: sidewalks, paths, walkways
Fixture Placement: center
Ideal mounting height: equal to walkway width

Type II

Pattern type: 25° lateral distribution
Applications: narrow roadways, wide walkways, ramps and entrance roadways
Fixture Placement: at or near the side
Ideal mounting height: width of road should not surpass 1.75 times the mounting height

Type III

Pattern type: 40° lateral distribution
Applications: conventional roadways, parking areas
Fixture Placement: at the side
Ideal mounting height: width of road should not surpass 2.75 times the mounting height

Type IV

Pattern type: 60° semicircular distribution
Applications: wide roadways, sides of walls or buildings
Fixture Placement: at the side
Ideal mounting height: width of road should not surpass 3.7 times the mounting height

Type V

Pattern type: 360° circular distribution
Applications: roadways, center parkway islands, intersections, large parking areas
Fixture Placement: at or near the center
Equal light distribution at all angles

Type VS

Pattern type: 360° square distribution
Applications: roadways, center parkway islands, intersections, large parking areas
Fixture Placement: at or near the center
Equal light distribution at all angles, used where the light pattern has a more defined edge

Dwayne Kula

 

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About the Author

Dwayne Kula is President of LED Lighting Supply. On any given day, Dwayne is writing content for the site and helps manage the marketing initiatives that are on-going. He has a Software Engineering degree and still dabbles in writing software for the company as needed. When not working, he enjoys spending time with his family, working out, playing the occasional game of golf and exploring New England.

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