the room are colored with a high-reflectance color. Lighting is, however, only one of many factors that make up the whole environment. While the highest lighting efficiency may be maintained in a completely white room, the psychological effect of such surroundings on the occupants may be less than harmonious. The use of color in the surroundings, even if it means sacrificing lighting efficiency, is necessary for the well-being of the occupants. Ceilings should have the lightest color, preferably an off-white. Shiny surfaces should be avoided, as they result in glare. As mentioned earlier, lighting levels start dropping immediately after the installation of the fixtures. Lamp burnouts and lamp depreciation contribute to this, but the principal cause is the accumulation of dirt. It is not uncommon to find lighting levels one half of the initial values after only a year or so of operation. The lighting maintenance program must include cleaning and painting of the walls and ceilings in addition to the fixture cleaning schedule.
When mounting any light fixture, follow the manufacturers step-by-step instructions. The most important thing to remember when mounting any fixture or device is to ensure that all connections are both electrically and mechanically secure. High-intensity discharge lamps (HID) will be discussed further in chapter 6.
As light sources are designed to operate most efficiently and economically at their rated voltages, special emphasis should be given to using lamps to suit the voltage of the circuit. Operation within the normal operating range is desirable; because both overvoltage and undervoltage operations have a determined effect on the life, efficiency, and economy of the light source. The effect on lamps operated over or under their rated voltage range is described below.
Line voltage higher than the maximum of the ballast range will shorten lamp and ballast life. Line voltage below the minimum range will reduce illumination and may cause uncertain starting of some types of fluorescent lamps.
Line voltage higher than the maximum lamp range will increase the light output but will shorten lamp life. Line voltage below the minimum range will extend lamp life but will reduce light output approximately 3 percent for each 1 percent in voltage drop.
Line voltage higher than the maximum lamp range will shorten lamp and ballast life. Line voltage below the minimum range will reduce illumination and may cause uncertain starting.
The most common troubles encountered with lamp equipment, the probable causes, and the suggested solutions are contained in table 5-6.
Lighting has a great influence on the quality and quantity of work as well as a direct bearing on employee morale. The necessity for periodic attention to the lighting system cannot be overemphasized. To prevent progressive deterioration of the system, personnel must provide regular maintenance and prompt repair of any deficiency.
Maintain the required illumination intensity by keeping lamps, fixtures, and reflective areas clean and in good repair; by replacing defective lamps; and by keeping the voltage steady.
It is well known that dirt absorbs and masks light. The progressive decrease of light caused by accumulat- ing dirt renders periodic cleaning of lighting equipment a necessity. The frequency of cleaning depends largely upon local conditions. Fixtures in air-conditioned and air-filtered rooms may require cleaning only once a year. In an atmosphere that is heavy with dust and fumes, cleaning every few weeks may be necessary.
The cleaning schedule for a particular installation should be determined by light meter readings after the initial cleaning. When subsequent foot-candle readings have dropped 20 to 25 percent, the fixtures should be cleaned again. Readings should be made with the light meter at the working surface with the meter reader in the position of the operator or person using the working surface.
Lighting equipment should be washed, not just wiped off with a dry cloth. Washing reclaims 5 to 10 percent more light than dry wiping and reduces the possibility of marring or scratching the reflecting surface of the fixtures.
To clean removable glassware, reflectors, and diffusing louvers, immerse them in a solution ofContinue Reading