can you please help me on this question 1 A 10000 sq ft Ware

can you please help me on this question

1) A 10,000 sq. ft Warehouse has 100 light fixtures evenly spaced 20 feet above the floor. The CU=.85 and the LLF=.7. Calculate the averaged maintained illuminance in footcandles and in lux, using the following fixture types:

a) 100 Watt High Pressure Sodium Fixture with white lamps

b) 70 Watt Metal Halide Fixture with phosphor-coated lamps

c) Which would you recommend and why.

788 i How LIGHT BEHAVEs usHING FUNDAMENTALS Foot candles 10x10 area of the room and still assume spread over the then same is average lighting doubled area, resulting in an To calculate lux, let us use the uminance, of half what is space uniformly lighted light evel, or il one, we approxima factor instead would have ux. fo is directly proportional to the area (lumens) proportional that the space. Expressed we say later how to We shall learn umination when given the and the room dimensions and fins point, we tha hax and Light flux Lumens (4.1) Illuminance ince lumensarea is simply flux density, we have dle are the important units of light shown that illuminance is the same as flux density. technologist practical given and layou nologist. In will be the Light flux density or illuminance is measured or and wil units of footcandles in the sh system of calculate the lighting required and to and units of lux in the metric (sn system in the These footca in units that nation levels are taken from uminances published by sources. In the United Sta English units this information is the Illumi Lumens (14.2) Foot candles ociety of North America (IESNA heada Square feet of area at 120 Wall Street, 17th floor, N or 0005-4001 These recommended illumi fairly complex, since they include consi of the type of activity for which the i SI (metric) units: being designed, the reflectance of t Lumens (14.3) and its surroundings, the age of the Square meters of area volved and speed and accuracy requirem taking all these factors into account, then give a recommended illumina which can be adjusted up or down b to compensate for other factors not incl Despite the fact that the United States st ables, such as day English units, lux is now used in the lighting pro- tion. As should be obvious, the selec fession at least as much as footcandles. It i there- a simple target illuminance is no fore, important for the technologist to be able to derable knowledge that requires const convert rapidly between the two systems. Since ence in lighting design. For this rea there are 10.76 ft2 in one square meter, there are including only a single table of recom 10.76 lux in one footcandle. Therefore, to convert minances for generic types of activ 14.1. Notice in the table that each Multiply footcandles by 10.76 to ge entry is composed of 3 numbers: a mi figure; a lower figure t Divide lux by 10.76 to get footcandles viewing conditions are excellent an For quick calculation, use 10 rather than 10.76. ure that is used for target illumina viewing conditions. You can find co The error introduced by this approximation is in the publications listed in about 7.5% Let us illustrate these simple relations. Suppose Reading section at the end of this ch In general, the technologist will that we have a light fixture in a room that causes 1000 lm to be distributed evenly on the floor. The target illuminance figure by the pr room is 10 ft square. What is the designer or lighting consultant. T umination on the floor in footcandles? in lux then use this figure to calculate

Solution

Use 70 Watt Metal Halide Fixture with phosphor-coated lamps because Luminus around same for 100 Watt High Pressure Sodium Fixture with white lamps, but efficiency is more in 70 watt metal Halide Fixture.