Light Source & Fixture Selection

The lighting design process in its most basic form entails identifying a task and then providing a light source that will provide proper quantity and quality of light for the task. The fixture protects the light source, connects it to the power source and distributes its light. Here we will review the basic factors that go into specifying a light source and a fixture.

Light Source Specification Checklist
The light source is the actual light-producing component of the lighting system. It may operate simply as a lamp (incandescent/halogen) or as a lamp powered by a ballast (fluorescent and high-intensity discharge [HID]).

Below are considerations for specifying three basic lamp types:

Incandescent Lamps

Do not require a ballast
Warm color appearance with a low color temperature and excellent color rendering (CRI 100)
Compact light source
Simple maintenance due to screw-in Edison base
Less efficacious light source
Shorter service life than other light sources in most cases
Filament is sensitive to vibrations and jarring
Bulb can get very hot during operation
Must be properly shielded because incandescent lamps can produce direct glare as a point source
Require proper line voltage as line voltage variations can severely affect light output and service life

Fluorescent Lamps

Require a ballast
Range of color temperatures and color rendering capabilities
Low surface brightness compared to point sources
Cooler operation
More efficacious compared to incandescent
Ambient temperatures and convection currents can affect light output and life
All fixtures installed indoors must use a Class P ballast that disconnects the ballast in the event it begins to overheat; high ballast operating temperatures can shorten ballast life
Options for starting methods and lamp current loadings
Requires compatibility with ballast
Low temperatures can affect starting unless a "cold weather" ballast is specified

HID Lamps

Require a ballast
Ambient temperature does not affect light output, although low ambient temperatures can affect starting, requiring a special ballast
Compact light source
High lumen packages
Point light source
Range of color temperatures and color rendering abilities depending on the lamp type
Long service life
Highly efficacious in many cases
Line voltage variations, possible line voltage drops, and circuits sized for high starting current requirements must be considered

Checklist for specifying the right lamp for the application:

Light output
Input wattage
Efficacy (lumens per watt)
Rated service life
Size
Surface brightness
Color characteristics
Electrical operating characteristics
Requirement of additional equipment such as ballasts
Compatibility with the electrical system
Suitability for the operating environment

Light Fixture Specification Checklist
A luminaire, often called a light fixture, is a complete lighting unit that produces and distributes light. It contains the light source, a ballast if the lamp is fluorescent or HID, components designed to diffuse or distribute the light in a controlled pattern, components to protect and position the lamp(s), and a connection to the power source.

The light fixture's basic function is to produce and distribute light to fulfill the design goals for the lighted space. Below is a checklist for specifying the right fixture for the job.

Characteristics of the Space
First, the specifier must fully understand the demands of the application and conditions in the space that will affect the operation of the lighting system:

Tasks to be performed in the space
Desired light levels based on the tasks performed in the space
Room size and dimensions
Structural obstructions such as beams
Layout of furniture and obstructions such as partitions
Room and object surface colors and reflectances
Special concerns such as safety and security
Hours of operation
Assessment of normal operating conditions
Possibility or known existence of abnormal operating conditions
Cleanliness of the area during operation
Maintenance schedule
Availability of daylight

Characteristics of Lighting Components and the Fixture
Now the most appropriate light source can be selected, followed by the fixture. The specifier must understand the factors affecting fixture selection:

Electrical, physical and operating characteristics of the light source selected
Electrical, physical and operating characteristics of appropriate ballasts
Electrical, physical and operating characteristics of controls to be employed
Fixture efficiency (% lamp light output transmitted out of the fixture)
Distribution pattern
Glare control
Finish
Appearance
Size
Accessibility of interior components for maintenance
Ability to handle abnormal as well as normal operating conditions
Aesthetics

Codale Electric Supply can work with you in the process of determining the lighting and fixture types that are right for your application. For more information please call us a 1-800-300-6634, e-mail custsvc@codale.com, or fill out the request form that can be found in the Contact Us section of this website.