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Metal Halide Lamps: Enclosed Rated vs Open Rated

Posted by on 1/4/2011
Enclosed Rated vs Open Rated Metal Halide Lamps
Depending on the type of fixture being used, metal halide lamps are available for both enclosed fixtures (ANSI/e) or open fixtures (ANSI/o, ANSI/s or ANSI/p). The /o, /s or /p are protected lamps, meaning they have a secondary protective filament casing and will not explode or catch fire. Open rated metal halide lamps are also called self-extinguishing due to this feature. Enclosed rated lamps will only operate in enclosed fixtures and that is due to the shorter lamp base (E39) whereas the open rated lamps have a longer lamp base (EX39). Because the EX39 base is longer, it will operate in both an enclosed fixture as well as an open fixture. Because of the added safety that the open rated lamps provide, they are widely used in enclosed fixtures even though it is not required.

Open Bottom High Bay Lighting Fixture

Open Rated High Bay Fixture

The most common type of open fixture is an open bottom high bay and they have the EX39 socket that require the longer lamp base for metal halide. *The EX39 porcelain sockets are usually pink and the E39 enclosed rated sockets are usually white.

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