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Questions and Answers
What is the final equation of the lumen method?
What is the final equation of the lumen method?
E = LxN x CU x LLD x LDD x RSDD x VF x BF
What is the floor area of the room in the given example?
What is the floor area of the room in the given example?
The floor area of the room is 10m x 6m.
What is the clearance from the slab to false ceiling level in the example?
What is the clearance from the slab to false ceiling level in the example?
The clearance from slab to false ceiling level is 0.25m.
What is the total height from floor to slab in the given example?
What is the total height from floor to slab in the given example?
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What is the required illuminance level for the room?
What is the required illuminance level for the room?
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What is the value of LLD considered for the LED luminaire?
What is the value of LLD considered for the LED luminaire?
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What is the type of environment mentioned in the example?
What is the type of environment mentioned in the example?
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What type of luminaire is mentioned in the example?
What type of luminaire is mentioned in the example?
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What does SHR stand for in the context of lighting design?
What does SHR stand for in the context of lighting design?
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What is the formula to calculate SHR?
What is the formula to calculate SHR?
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Study Notes
Lighting Calculation Overview
- Calculate illuminance using the formula: E = A, where E is illuminance, A is area, factoring in light loss factors (LLF).
- Maintained illuminance considers light loss from various factors over time.
Light Loss Factors (LLF)
- Two categories: recoverable and non-recoverable.
- Recoverable Light Loss Factors can be mitigated through maintenance.
- Non-recoverable Light Loss Factors cannot be eliminated.
Recoverable Light Loss Factors
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Lamp Lumen Depreciation (LLD): Decrease in lamp lumen output over time.
- Calculated as: LLD = Mean Lumens / Initial Lumens.
- Values vary by lamp type:
- Incandescent: 0.92
- Halogen: 0.95
- T5 Linear Fluorescent: 0.95-0.97
- T8 Linear Fluorescent: 0.92-0.95
- Compact Fluorescent: 0.85-0.90
- Quartz Metal Halide: 0.65-0.80
- Ceramic Metal Halide: 0.80-0.90
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Lamp Dirt Depreciation Factor (LDD): Reduction due to dirt on fixtures and lamps.
- It depends on luminaire type and environmental dirt levels.
- Factors for environment classification: clean, moderate, dirty.
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Room Surface Dirt Depreciation (RSDD): Affected by:
- Amount of dirt present.
- Room cavity ratio.
- Luminaire type.
Non-Recoverable Light Loss Factors
- Voltage Factor (VF): Variations in lumen output caused by voltage deviations from rated levels, especially in incandescent lamps.
- Ballast Factor (BF): Indicates if the ballast drives the lamp correctly. Under-driving or over-driving results in lumen output variations.
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Description
Test your knowledge on lighting calculations in buildings with this quiz based on Lecture 4-2 of BS304010 Lighting Systems in Buildings by P.M Perera. Calculate the illuminance of a work plane in a room with specific lighting parameters and factors to consider. Evaluate the impact of light loss factors on maintained illuminance levels.
