In this course you will learn:
- How to inspect fluorescent lighting fixtures and incandescent lighting fixtures (Fig.1),
- How to identify the correct fixture to be inspected,
- How to verify that the fixture is properly installed,
- How to document your inspection results.
This course will reference the National Electric Code (NEC) and Underwriters Laboratory (UL) documents.
|Fig.1: Fluorescent and Incandescent Lighting Fixtures|
2- Verify that the Correct Fixture is being inspected
First: Incandescent Light Fixtures
- The incandescent lamp consists of a filament which is a highly refractory conductor mounted in a transparent or translucent glass bulb and provided with a suitable electrically connecting base. The filament is heated by the passage of an electric current through it to such a high temperature that it becomes incandescent and emits light. The older types of bulbs had the air inside of them removed. The modern lamps today have this space filled with an inert transparent gas such as nitrogen.
- (Fig.2) shows porcelain, single lamp, incandescent light fixture and a lamp. When the lamp is attached, the fixture operates as a common unit. The incandescent light fixture can be designed to hold one of several types of lamps. This type of fixture is used with a screw—type lamp base or cap.
|Fig.2: A Standard Incandescent Light Fixture and a Lamp|
- The incandescent lamp is widely used in many applications and often seen in the home. The life expectancy of an incandescent lamp is much less than a fluorescent lamp. The incandescent lamp is identified by the filament. The filament is made from a metallic material called tungsten. (Fig.3) shows a heavy duty lamp used for construction work.
|Fig.3: Basic Construction of a Standard Incandescent Lamp|
Classification of incandescent Lamps
Incandescent lamps can be classified in six different ways, according to:
1- Class of lamp
3- Shape of bulb
Incandescent lamps come in various shapes and sizes (fig.5), all designated by a letter or letters followed by a number. The letter is to identify the lamp's shape while the numerical designation is to identify the diameter of the lamp in an eighth of an inch. Example:
Lamp model 60A19, means :
60: Wattage (60 W) A: Bulb shape 19: Maximum bulb diameter, in eighths of an inch. (19 ÷ 8 = 2.38 in)
4- Bulb finishes
Incandescent bulbs can be finished in a variety of different ways. Some of the more popular ones are listed below:
5- Type of filament
Several different types of filament structures are used (fig.6). The filament structure is designated by a letter or letters to indicate whether the wire is straight or coiled and by an arbitrary number sometimes followed by a letter to indicate the arrangement of the filament on the supports. Prefix letters include:
S = straight; wire is straight or slightly corrugated
C = coil; wire is wound into a helical coil or it may be deeply fluted.
CC = Coiled coils; wire is wound into a helical coil, and this coil wire is again wound into a helical coil.
The below table include the most Common Filament types for Incandescent lamps.
6- Type of service
Incandescent bulbs are manufactured for a wide range of services, most of which can be classified into three categories:
In the next Article, I will explain Fluorescent Lighting Fixtures and its Components. Please keep following,