Westinghouse OV-20 Mercury Luminaires

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A very common style in the 1950's and 1960's for urban, highway, and other high light level applications, probably second in popularity to General Electric's Form 109.

They accommodate mercury lamps up to 400 watts, mounted horizontally. The ballast is sold and mounted separately.

Also available for incandescent lamps or for hanging from a span wire, with a top center mounted cylindrical incandescent luminaire's head.

The early style (early 1950's, also (?) late 1940's) had a double walled stamped sheet aluminum body. The polished reflector fit closely inside the body shell, and was not easily replaceable separately.

This specimen (top photo) has the more or less elliptical (football shaped) refractor. Most have the cylindrical section refractor (bottom photo).

The refractor is held in the mounting ring with two large U-shaped clips which can be seen in the right photo.

Weight: 16-1/2 lb.
Length: 24" overall. A ruler or drawn line in the photo indicates one foot although there is some distortion due to depth perspective.
Numbers molded on rim of refractor: 1373664 IES TYPE 2 A8III BIII
Numbers stamped on underside of body, near hinge: 678901 D or (?) 679901 D

The late style (lower left photo) was introduced ca.1956 and advertised as having a "strong one piece cast aluminum body". It, too, was "double walled" with a replaceable stamped aluminum highly polished reflector inside. I would have thought that the stamped body of the early style OV-20 was superior due to lighter weight. Indeed, about this time GE came out with a competing clamshell style model in stamped aluminum, the Form 400.

The refractor is held in a grooved cast aluminum mounting ring with a split on one side held together with a bolt. Shown is a protrusion in the lower rim of the body to allow room for the bolt to fit inside. Some versions had the split at the nose latch.

This fixture has an "automatic latch that permits one hand closure" which I take to mean you slam it shut.

A spring steel strip at the hinge and a spring in the nose latch hold the refractor tight against body to eliminate glass destroying rattle from street vibration and to keep insects out.

This unit was mounted on the ceiling as part of our display and we haven't taken it down for weighing yet. Length: 25-1/2 in. overall.

There are so many variations of the OV-20 that I would have thought different model names should have been assigned.

1. Mounting and Lamp Type

a. End  (horizontal pipe) mount, no separate cylindrical head
b. Top (vertical pipe) mount mercury, empty incandescent style head on top
c. Top mount incandescent, with vertical lamp socket in head on top
d. Side (horizontal pipe) mount mercury, empty head with mounting collar on top
e. Side mount incandescent, with head for vertical lamp socket

2. Body material

a. Stamped aluminum
b. Cast aluminum
(possibly minute differences as improvements over the years)

3. Refractor

a. Football section (round profile)
b. Cylindrical section (flat profile)
(different refractors within each style for different light distribution patterns)

Just the variations listed give a total of twenty different combinations.