Depreciation of light emissions

Depreciation of light emissions

Illumination:

Illumination initially provided by a lighting installation will gradually fade over the course of its use due to reduced number of lamps, lamp burning, and dirt build-up in lamps, fixtures and room surfaces.

Dirty surface of fluorescent lamp

However, it is possible to keep the illumination equal to or above the minimum allowable value (called the maintenance value), clean lighting fixtures and room surfaces, as well as replace burnt out or worn lamps at suitable intervals, according to a previously agreed maintenance program.

The value of this maintenance schedule is shown in Figure 1. Clearly, in the case illustrated, the illuminance in the unmaintained system will decrease to 40% of the initial value during the first three years and continue to decrease.

But with an annual cleaning, a paint change and a paint change every three years, the shine reaches 60% of the original value.

In three years, the updated system provides 50% more illumination than the maintenance-free system.

Light Emissions

Factors to consider in interior lighting depreciation

Dirt in lamps and fixtures

In most cases, light loss can be attributed to dirt accumulated in lamps and light control surfaces (reflected, refracted, or scattered) of fixtures.

Damping rate caused by dirt that the inclination, finish and temperature of the surface, the degree of ventilation or tightness of the fixture, as well as the degree of air pollution around the fixture affect the build-up on the fixture. light control surfaces.

Damping of light emission can be reduced by choosing the right fixtures for each location. Open-base and closed-surface fixtures accumulate dirt faster than ventilated ones. In ventilated luminaires, convection currents remove dust and dirt through holes or slits in the canopy or reflector and reflective surfaces.

In highly polluted environments, it is best to use waterproof or dustproof luminaires. Some of them have a filter inside which allows the necessary "breathing".

Dirt on room surfaces

Dirt accumulated on ceilings (flat ceilings) and walls reduce their reflectance value and, therefore, the amount of reflected light. The connection between this and the illuminance calculation will obviously depend on the size of the room to be studied and the light distribution of the luminaire.

The effect will be more pronounced in small rooms or when there are fixtures with indirect component.

Lamp flux depreciation

The luminous performance of all lamps decreases with use, but the rate of this decrease varies considerably between types of lamps and manufacturers.

Therefore, lighting calculations must take into account Mind specifies the depreciation of the luminous performance of each particular lamp. It should be taken into account that the figures are based on certain assumptions relating to working conditions.

One or more of the following factors may influence the depreciation index:

• Ambient temperature

• lamp working position

• voltage supplied

• Type of control equipment used, if applicable

Lamp failure

The average life of a lamp depends on the type of lamp used and, for gas discharge lamps, on the ignition cycle. Lamp failures not only lead to a reduction in lighting levels, but also an unacceptable reduction in the degree of uniformity of lighting.

Maintenance factor (f m)

F m is defined as the ratio between the illumination produced by the lighting installation at a specified time, to the illumination produced by the installation itself when it is new.

F m thus combines the losses caused by the damping flow, damping of the luminaires and damping of the room surface. If each of these causes of depreciation is quantified by a specific period of use, a general factor product of the three factors is obtained.

F m = lamp flux loss factor x luminaire loss factor x room area loss factor

When the light loss factor for different maintenance situations is calculated, it is possible to predict the lighting situation produced by the installation as a function of the elapsed time.

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