Installing
Convenience Devices

[lesson title]

BASIC INCANDESCENT LIGHTING FIXTURES

The fixture in Figure 3-1 is made of porcelain or plastic and is designed to help keep fingers off the hot terminal.

Figure 3-1.   Incandescent light fixture

The hot terminal will be located at the bottom of the fixture; it is the center strip at the bottom of the fixture. The neutral is the threaded side of the fixture (Figure 3-2).

Figure 3-2.   Hot/neutral terminal

Some simple lamp fixtures have their own switch or pull chain. The pull chain is the simplest type control for a light fixture (Figure 3-3).

Figure 3-3.   Light fixture with pull chain

A brass-shell socket is one of the most widely used fixtures. This socket is used in lamps and can also be found with a twist knob or push buttons (Figure 3-4).

Figure 3-4.   Brass-shell socket

There are several different ways to hang heavy or large light fixtures in boxes. Figure 3-5 shows a strap and a nipple being used for support. Before heavy fixtures are installed, ensure that the outlet box is adequately attached to the structure. Most ceiling finishes do not provide adequate support for heavy fixtures. This setup is the most widely used with a standard fixture.

Figure 3-5.   Standard fixture with strap-and-nipple support

Figure 3-6 shows a fixture stud being used for extra support. The stud-and-nipple combination is a good way to hang heavy fixtures. In this situation, the stud is attached directly through the back of the outlet box.

Figure 3-6. Fixture stud used for extra support

The light fixture is hung by slipping it over the nipple and holding it in place with a cap nut. When installed correctly, the fixture is electrically safe and will retard a fire for a short time (Figure 3-7).

Figure 3-7. Installing light fixture

When hanging fixtures, some basic procedures must be followed to ensure a safe installation (Figure 3-8).

Figure 3-8. Safe installation procedures

Shades or reflectors are manufactured in various shapes of metal, glass, mirrored glass, prismatic glass, and opaque materials (Figure 3-9).

Figure 3-9. Shades and reflectors

There are five types of reflectors which correspond to the five types of lighting areas: direct, semidirect, general diffused, semi-indirect, and indirect. In direct lighting, the reflector allows practically all light (90 to 100 percent) to be directed toward the work area. This type of reflector creates shadows, direct glare, and reflected glare (Figure 3-10).

Figure 3-10.   Direct lighting

As shown in Figure 3-11, a glass reflector directs 60 to 90 percent of the light toward the work area, and 10 to 40 percent toward the sides and top of the globe. The globe is good for stairways, corridors, and storage areas.

Figure 3-11.   Semidirect lighting

Figure 3-12 shows general diffused lighting. Light is equally supplied in all directions. This type of globe can be bad because of excessive brightness and glare (Figure 3-12).

Figure 3-12.   General diffused lighting

In semi-indirect lighting, some of the lighting (10 to 40 percent) is directed to the work area, but most of the light (60 to 90 percent) goes to the upper walls and ceilings. This fixture gives a good overall lighting with low surface brightness and low glare (Figure 3-13).

Figure 3-13.   Semi-indirect lighting

In indirect lighting, most of the light (90 to 100 percent) is reflected onto the ceiling and the entire ceiling becomes a light source, thus eliminating shadows and glares. Indirect lighting is good in an office, a schoolroom, or in areas used for close work where eye strain may occur (Figure 3-14).

Figure 3-14.   Indirect lighting

Incandescent light fixtures are manufactured in different designs, sizes, and shapes. They have basic components and can be mounted on ceilings and walls ( Figure 3-15).

Figure 3-15.   Incandescent light fixtures

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