Lampholders are mechanical devices that support lamps and connect them to electrical circuits. They hold light bulbs and make electrical contact to provide a bulb with power. Lampholders are used with most light sources for incandescent, fluorescent, and compact fluorescent lamps (CFL).
Fluorescent vs. Incandescent Lamps
Incandescent lamps utilize incandescent (normal) bulbs which house a thin tungsten filament inside a glass sphere. Because the wire is thin, it offers resistance to electricity and converts electrical energy into heat which generates white light.
Fluorescent lamps utilize fluorescent bulbs which house electrodes at both ends of the tube and argon and mercury vapor throughout. A phosphor coating on the inside of the tube emits light through emission of ultraviolet light from excitation and stabilization of mercury atoms. Fluorescent bulbs tend to be more energy efficient and longer lasting than incandescent bulbs.
Types of Lampholders
There are four categories of fluorescent lampholders: compact, starter base, linear, and miscellaneous.
- Compact products have round or standard bodies and are available for most 2-pin and 4-pin lamp bases. These lampholders carry product specifications for lamp life, wattage, and voltage.
- Starter base products are lampholders with a starter base attached (where the starter is installed). These lampholders also carry product specifications for lamp life, wattage, and voltage.
- Linear lampholders are specified by contact type, lamp base, lamp contacts, lamp type, and mounting style. Choices for contact type include automatic lock, lamp lock, plunger, stationary, straight-in double edge, and turn.
- Miscellaneous fluorescent lampholders are typically plug-in products with a circle-line lamp base and 4-pin contacts.
Incandescent lampholders may be divided into the following categories: candle socket, multi-cluster, shell, and adapters and extenders.
- Candle socket products are designed for one or two circuits and feature a one-piece or two-piece construction. The turn knob may be integral or removable with either back wiring or a side outlet.
- Multi-cluster designs have either two or three lights and are designated as keyless or pull chain. Pull chain holders utilize a chain to turn current on and off while keyless holders rely on an external switch for control. Both pull chain and keyless lampholders may have a shell made of aluminum or porcelain.
- Shell lampholders use a screw-in design and are available in both standard configurations and with dimmers.
- Socket adapters and extensions are specified by lamp base, with choices such as mogul-medium, medium-medium, and mogul-mogul.
Lampholders for CFL, HID, and halogen lamps are also available. CFL lampholders are an energy-efficient alternative to incandescent lamps and may comply with NFPA 70, NEC Section 410.16 requirements. HID lampholders are available for various lamp types, too, and may include a leaf spring under contact or screw shell reinforcing washers. Halogen lampholders are specified according to ANSI lamp type. Specialty lampholders for other light sources and applications are also available.