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Questions and Answers
What is the basic unit of measurement for luminous flux?
What is the basic unit of measurement for luminous flux?
lumen
What is the basic unit of measurement for luminous intensity?
What is the basic unit of measurement for luminous intensity?
candela
What is the basic unit of measurement for illuminance?
What is the basic unit of measurement for illuminance?
lux
What is the basic unit of measurement for luminous efficacy?
What is the basic unit of measurement for luminous efficacy?
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What are the two main types of light sources?
What are the two main types of light sources?
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Lighting design is purely a scientific process.
Lighting design is purely a scientific process.
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Which of the following factors is NOT typically considered when designing indoor lighting?
Which of the following factors is NOT typically considered when designing indoor lighting?
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What does the acronym 'IESNA' stand for?
What does the acronym 'IESNA' stand for?
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Which of the following is NOT a factor considered when determining the quality of light?
Which of the following is NOT a factor considered when determining the quality of light?
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What is the coefficient of utilization (CU) in lighting design?
What is the coefficient of utilization (CU) in lighting design?
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What does 'LLF' stand for in lighting design?
What does 'LLF' stand for in lighting design?
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The Lumen method is used to calculate the illuminance at a single point in the room.
The Lumen method is used to calculate the illuminance at a single point in the room.
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What is the recommended illumination level for dining rooms according to IESNA?
What is the recommended illumination level for dining rooms according to IESNA?
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Which type of light fixture typically has the lowest recommended spacing-to-mounting height (s/mh) ratio?
Which type of light fixture typically has the lowest recommended spacing-to-mounting height (s/mh) ratio?
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The Lumen method is suitable for designing task lighting, like a reading lamp on a desk.
The Lumen method is suitable for designing task lighting, like a reading lamp on a desk.
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The formula for calculating the number of luminaires needed in a space takes into account the light loss factor (LLF).
The formula for calculating the number of luminaires needed in a space takes into account the light loss factor (LLF).
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What is the general approach to designing a lighting system?
What is the general approach to designing a lighting system?
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Direct concentrating luminaires produce a wide beam spread.
Direct concentrating luminaires produce a wide beam spread.
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The mounting height of luminaires dramatically affects the illuminance level in a space.
The mounting height of luminaires dramatically affects the illuminance level in a space.
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Study Notes
Illumination Design
- Light is a form of radiant energy from natural (sun, stars) and artificial (candles, lamps) sources.
- Light travels as an electromagnetic wave with a known wavelength and speed.
- Light can be reflected and refracted.
- Lighting is the application of light to illuminate objects, surfaces, scenes, pictures, and people.
Presenter Information
- The presenter is a newly passed Professional Electrical Engineer.
- They have 12 years of experience in government service as a City Electrical Engineer.
- They were a former Overseas Filipino Worker (OFW).
- They were a former Barangay Electrician.
- They are a 3-time IIEE Chapter President of IIEE Sorsogon.
Introduction
- Light is a form of radiant energy from natural (sun, stars) and artificial (candles, lamps) sources.
- Light travels as an electromagnetic wave.
- Light has a known speed and wavelength.
- Light can be reflected and refracted.
Lighting Concepts and Units
- Luminous flux (Φ): The total radiated power emitted by a light source. It's the light output of a light source. Unit: lumen (lm).
- Luminous intensity: The visible radiant intensity in a particular direction. Unit: candela (cd).
- Illuminance (E): A measure of the amount of light falling on a surface. Unit: lux (lx). It's the average illumination of a surface from luminous flux per unit area. (lux = lumens/m²)
- Luminous efficacy (η): Indicates the efficiency of a light source. Measured in lumens per watt (lm/W). This shows how well the electrical power is converted to light.
Lighting System Design
- The design of an indoor lighting system is more of an art than science.
- Many variable factors influence this design, including the space's dimensions and shape. Finishes of ceilings, walls, and floors are also essential.
- Construction details, cost (initial and operating), compatibility with the architectural design, and the activities performed in that area all need to be considered.
Objectives and Design Considerations
- Determination of required illumination level
- Quality of illumination needed
- Quantity of illumination needed
- Area atmosphere analysis (dirt, water vapor, presence of explosive/corrosive materials)
- Space description and use (room dimensions, reflectance, location of work area)
- Selection of the lighting system's luminaire.
Determination of Required Level of Illumination
- Refer to a table of recommended illumination levels specific to different occupancy types.
- The table used is provided by the Illuminating Engineering Society of North America (IESNA).
Quality of Light
- Distribution of brightness in the installation, relates to the comfort of seeing the environment.
- Factors affecting quality include brightness, contrast (or luminance ratio), glare, diffuseness, and color.
Quantity of Light
- Adequate illumination level for the average person under normal conditions.
- Analysis of the environmental operating conditions (i.e. dirt, water vapor, explosive gases, corrosive vapors).
Area Description and Use
- Full description of the area to be lit.
- This includes physical characteristics: dimensions, room reflectance, and work location
Determining Average Illuminance
- Average illuminance level can be determined when the number of luminaires is known.
- The number of luminaires can be determined given the average illuminance level.
- Work surface illuminance is measured at 0.75m above the floor in an office, or at floor level in corridors
The General Equation
-
Ewp = (Φtotal x CU x LLF) / Awp
-
Where: Ewp = Work plane illuminance, Φtotal = total system lamp lumen output, CU = coefficient of utilization, LLF = light loss factor, Awp = work plane area
Work Plane Illuminance (Ewp)
- Average maintained luminous flux hitting the work plane per unit area.
- Measurement unit: lux (lx)
Total System Lamp Lumen Output (Φtotal)
- Quantity of light produced by all lamps in a space.
Coefficient of Utilization (CU)
- Ratio of lumens reaching the work plane to the total lumens provided by the lighting system.
Light Loss Factor (LLF)
- Ratio of illuminance when it reaches a lower level (just before correction) to the initial level.
- Product of all individual factors contributing to light loss.
- Also called the maintenance factor.
LLF Equation
- LLF = LLD x LDD x RSDD
- LLD: Lamp Lumen Depreciation Factor (lumen output depreciation over the lamp's lifetime)
- LDD: Lamp Dirt Depreciation Factor (dirt accumulation causing light loss)
- RSDD: Room Surface Dirt Depreciation Factor (accumulation of dirt on room surfaces reduces light reaching the work plane)
Indoor Lighting Calculation (Lumen Method)
- Method for overall room lighting design (general lighting)
- Calculates the average illuminance over the entire work plane.
Average Illuminance (E)
- E = (TILL x CU x LLF) / Area
- TILL: total initial lamp lumens
Sample Simplified Calculation
- Determine if two 36W T8 fluorescent lamps are enough to illuminate a 3m x 4m dining area.
- Consideration of CU (0.65) and LLF (0.95).
- Calculation results in an illuminance of 334.78 lx.
Table of Recommended Illumination
- IESNA recommends 540 lx for dining rooms.
- Two 36W T8 fluorescent lamps are insufficient.
- Three sets are required.
Uniformity of Light
- Average illumination on the work plane is related to the maximum spacing of luminaires vs the mounting height.
- Ratio = S/MH (S = spacing, MH = mounting height). Different types of light fixtures have different recommended S/MH ratios.
Recommended Spacing and Mounting Height Ratio
- Different types of light fixtures (e.g., direct concentrating, direct spread, diffused, semi-direct/indirect) have different optimal spacing-to-mounting-height ratios.
Example Calculation—Office Room
- Calculate the number of 3-lamp 36W FL parabolic troffers required for an 8m x 20m office with 1600 lx illumination, CU 0.65, LLF 0.85, and 335000 lumens per lamp.
- Calculation results in 24-28 sets.
General Information
- Illumination design combines basic lighting terms and mathematical/graphical techniques.
- Methods and calculations follow recommendations from the IESNA.
- Formulas provide general overview, not comprehensive illumination calculation for a design.
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Description
This quiz explores the fundamental principles of illumination design, covering the nature of light, its travel as an electromagnetic wave, and its application in various sources. Understand key concepts such as luminous flux and the properties of reflection and refraction. Ideal for those interested in electrical engineering and lighting applications.
