Occupancy

• a legal term building construction and building codes. It refers to the use or intended use of a building or part thereof for the shelter or support of persons, animals or property. A closely-related meaning is the number of units in such a building that rented or leased, or otherwise in-use. The lack of occupancy in this sense is a vacancy.

Lighting control system

• consists of a device, typically an embedded processor or industrial computer, that controls electric lights for a building or residence. Lighting control systems usually include one or more keypads or touch panel interfaces. These interfaces allow users the ability to toggle power to lights and fans, dim lights, and program lighting levels.

A major advantage of a lighting control system over conventional lighting is the ability to control any device from any interface. For example, a master touch panel might allow the user the ability to control all lights in a building, not just a single room. In fact, any light might be controlled from any location.

Other benefits include reduced energy consumption and costs (through more efficient usage), longer bulb life (through dimming), and reduced emissions. Newer, wireless lighting control systems provide additional benefits including reduced installation costs and increased flexibility in where switches and sensors can be placed.

POINT-BY-POINT METHOD

Laws of Illumination:

• the illumination is directly proportional to the luminous intensity of the light source.
• the illumination varies inversely as the squae of the distance from the source of the light.
• the illumination varies directly as the cosine of the angle between the normal to the surface and the direction of the incident light.

L=Φ/4π Eρ=(l/d²) cosθ

Note: Normal line is a line perpendicular to the surface considered. Incident light is the ray of light that strikes the point of interest.

where:

• Eρ= intensity of illumination
• d= distance of the lamp from the point of interest(point P)
• l= candle power of the lamp(candela or candles)
• θ = angle between the incident ray and the normal line also called angle of incidence
• Φ= total lumen output of the lamp

Illumination(E) Candle Power(l) Distance(d)

Foot-candle Candela foot Lux Candela Meter phot candela Centimeter

POINT BY POINT METHOD(three-dimensional plane)

Eρ= lz/(x²+y²+z²)³/²

where:

• x=length
• y=width
• z=elevation of the lamp from the x-y plane

ZONAL CAVITY OR AVERAGE ILLUMINATION METHOD

Einitial= (ΦxNxCu)/A Emaintained=(ΦxNxCuxDf)/A

WHERE:

• Einitial= illumination when the installation is new
• Emaintained=average or maintained illumination
• N= no. of lamps
• Cu= coefficient of utilization
• Df= derweciation or maintenance factor
• Φ= lumen output per lamp
• A=surface area illuminated

Illumination(E) Area(A)

foot-candle ft²

lux m²

phot cm²

Note: the value Cu and Df are evaluated using standard graphs in the Electrical Engineering Handbook. Usually in problem solving exercises, these values are always givn (if not being asked)