When you turn on a lighting fixture, light travels through the light source (lamp or ballast) and the lighting fixture (such as a lamp shade or lensed troffer), until it reaches the work plane where it is needed. Along the way, the amount of transmitted light is reduced, obscured by the light source, the lighting fixture, and other environmental factors. The Light Loss Factor measures the reduction of light as it travels from the light source.
When defining the Light Loss Factor for a light, define the parameters as follows. Check with the lamp manufacturer for the appropriate Light Loss Factor values for a particular type of lamp.
| Parameter | Description |
|---|---|
| Temperature Loss/Gain Factor | For fluorescent light sources, a measure of the amount of light lost or gained due to deviations above or below the ideal operating temperature. Valid values are between 0 and 2. A value of 1.0 indicates that no light is lost or gained due to temperature changes. Values greater than 1.0 indicate an increase in light. Values less than 1.0 indicate a loss of light. |
| Voltage Loss/Gain Factor | A measure of the amount of light lost or gained due to fluctuations in voltage delivered to the light source. Valid values are between 0 and 2. A value of 1.0 indicates that no light is lost or gained due to voltage changes. Values greater than 1.0 indicate an increase in light. Values less than 1.0 indicate a loss of light. |
| Ballast Loss Factor | Lamps and ballasts experience losses when operating together as a system. The Ballast Loss Factor is the percentage of a lamp’s initial rated lumens that is produced by a given ballast. Valid values are between 0 and 1. For example, a value of 0.95 indicates that the ballast produces 95% of its initial lumens and loses 5%. |
| Lamp Tilt Loss Factor | For metal halide lamps, a measure of the amount of light lost due to the position of the lamp. A decrease in light occurs when the angle of the lamp shifts the cold spot of the bulb. Values less than 1.0 indicate a loss of light. |
| Surface Depreciation Factor | A measure of the amount of light lost due to deterioration of the surfaces of the lighting fixture as it ages. For example, blemishes and discolored shielding materials change the amount of light emitted. Values less than 1.0 indicate a loss of light. |
| Lamp Lumen Depreciation | As a lamp ages, it produces decreasing amounts of light on a predictable curve. A typical strategy is to use an average Lamp Lumen Depreciation (LLD) value at 40% of its life. Valid values are between 0 and 1. For example, a compact fluorescent has an LLD factor of 0.85, indicating an average output at 85% of its initial lumens, losing an average of 15% over its life as the lamp ages. |
| Luminaire Dirt Depreciation | A measure of the amount of light lost due to environmental dirt and dust that is trapped by the lighting fixture. Valid values are between 0 and 1. For example, a value of 0.9 indicates that the fixture produces 90% of its initial lumens and loses 10% due to trapped dust and dirt. |
| Total Light Loss Factor | A measure of the amount of light produced by a lamp, taking into account various environmental factors that obscure or reduce the emitted light. When the Method is Simple, use the slider or text box to specify a value. When the Method is Advanced, this parameter displays a read-only value, which is calculated by multiplying the values of the other parameters. Valid values are between 0 (total light loss) and 4 (light gain up to 400%). A value of 1 indicates no light loss (100% of initial light intensity). |