Willis Lamm's
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Lithonia 175 Watt Mercury Vapor Street Light |
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Around 1963 a design standard came out generally referred to as the NEMA Head. This head had a standardized opening to which reflectors and reflector / refractor assemblies would fit up to and attached via standardized lever latches. Early mercury vapor lamps had remote ballasts, but eventually ballasts were designed that fit into the head.
The Lithonia lamp came with an internal ballast and was relatively inexpensive. The most common refractor used was one was commonly called a "bucket," being slightly cone shaped with an open bottom, and providing omnidirectional lighting. These luminaires typically powered 175 watt Mercury Vapor lamps and were popular for low intensity area lighting, particularly along smaller residential streets where omnidirectional street lighting also provided some security lighting for nearby residences. |
The primary components: Reflector and refractor, NEMA style housing, photo control, mercury vapor ballast and lamp. |
The lamp assembled. |
| Some models could be mounted on standard street light arms, but also had small mounting ears so that they could be directly mounted to the sides of buildings. |
Typical industrial installation. |
Installed in the signal collection. |
| This refractor design threw a great deal of light out and up, and while they are still popular for industrial area lighting, many municipalities are replacing them with partial and full cutoff type luminaires in order to reduce "light pollution." |
| A Little Bit About NEMA |
| NEMA is basically a standardized housing design where reflectors and refractors had a common mounting configuration, were secured to luminaires with lever latches, and were interchangeable. Some of the lower wattage mercury vapor and sodium vapor luminaires were built to the NEMA standard diameter and had tabs for latching NEMA reflectors, but they also accommodated smaller reflectors that attached with screws to the lamp socket frame. This particular lamp came with the "industrial" style reflector and plastic refractor, although it could accommodate a NEMA reflector. |
Luminaire with NEMA reflector attached.
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A lamp on the street with full sized reflector & refractor.
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