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Note 54. Incandescent Lighting

The incandescent light bulb is one of the marvels of civilization. It was the achievement that made Thomas Edison famous. Unfortunately, it is a relatively inefficient method of lighting. The Energy Efficiency Manual has a large group of energy conservation measures devoted to improving the efficiency of incandescent lighting.

The Note explains how incandescent lighting works, why it is not efficient, the color spectrum of incandescent lamps, and the color rendering (CRI) of incandescent lamps. With this background, you will know where to use incandescent lighting and where to avoid it. The Note also provides practical information that will help you select the right lamps for applications where incandescent lighting is appropriate.

The characteristics of incandescent lamps are determined largely by the filament temperature. The Note explains limitations in filament materials, especially the properties of tungsten. It explains the relationships of light output, energy efficiency, color, and service life to filament temperature.

The Note explains the methods that are used to improve incandescent lamp efficiency. These include heavy fill gases, such as krypton, the tungsten halogen cycle, infrared reflecting coatings, and low-voltage filaments.

An enormous variety of incandescent lamp types are available. Here are your choices for wattage, lamp shape, lamp base or socket type, filament configuration, service life, efficiency and efficacy (lumens per watt), lumen depreciation, service life, lumen degradation, and other options. Also, you will learn the naming system for incandescent lamps, such as PAR lamps, reflector lamps, floodlamps, medium and mogul bases, and more.