Chapter 17: Lighting Equipment and Systems

17.1 Lighting accounts for what % of U.S. electrical energy use?

≈ 15–20% (significant portion of building energy use).;

17.2 Define luminous efficacy.

Lumens per watt (lm/W) → measures efficiency of converting electrical power to light.;

17.3 Theoretical lumens per watt?

(a) 600 lm/W (maximum theoretical efficacy of visible light).;

17.4 Fluorescent lamps introduced when?

1930s.;

17.5 Rated lamp life based on what % still burning?

50% (median life).;

17.6 LED rated life based on % of initial lumens?

70% (L70 rating).;

17.7 Which has higher color temperature: warm or cool light?

Cool light (higher Kelvin = bluer appearance).;

17.8 CRI of incandescent = 100 → perfect color?

True; used as reference source (excellent color rendering).;

17.9 What does PAR stand for?

Parabolic Aluminized Reflector.;

17.10 Max diameter: PAR38 and T5?

PAR38 = 38/8 = 4.75 in; T5 = 5/8 in.;

17.11 Fluorescent lamp life based on operating cycle?

3 hours per start.;

17.12 Fluorescent lamps fixed at 3500 K?

False; available in wide range (~2700–6500 K).;

17.13 Rank HID efficacy (low→high)?

Mercury < Metal Halide < High-Pressure Sodium (HPS).;

17.14 Rank HID color temp (low→high)?

HPS (warmest) < Mercury < Metal Halide (coolest).;

17.15 Characteristics of metal halide lamps?

Good color rendering, high efficacy, used in commercial/industrial lighting.;

17.16 Max efficacy of HPS lamps?

≈ 140 lm/W (very efficient).;

17.17 All incandescent lamps same color temp?

False; varies slightly with design and voltage.;

17.18 Magnetic ballasts obsolete?

Mostly true; electronic ballasts are more efficient and common today.;

17.19 Where are MR16/MR11 used?

Accent lighting, retail displays, spot lighting.;

17.20 HPS good for parking lots?

True; high efficiency and long life, though poor color rendering.;

17.21 Why use ceramic metal halide in big box stores?

Good color, high efficiency, long life → enhances product appearance.;

17.22 Two key luminaire photometric data?

Candela distribution and lumen output (light distribution pattern).;

17.23 Other factors in fixture selection?

Aesthetics, glare control, maintenance, efficiency, and light distribution.;

17.24 Approx lamp life?

Incandescent: ~1000 hr; Fluorescent/HID: ~10,000–20,000 hr; LED: ~50,000+ hr.;

17.25 Typical efficacy ranges?

Incandescent: 10–20 lm/W; Fluorescent: 60–100 lm/W; HID: 80–140 lm/W; LED: 80–200 lm/W.;

17.26 How do fluorescent lamps produce light?

Electric arc excites mercury vapor → UV light → phosphor coating converts UV to visible light.;

17.27 How do HID lamps produce light?

Arc through gas/vapor → emits intense light (depends on gas type).;

17.28 How do LEDs produce light?

Electroluminescence → electrons recombine in semiconductor → emit photons.;

17.29 Optimal temp for fluorescent lamps?

Bulb wall ≈ 100°F; ambient ≈ 77°F (best efficiency).;

17.30 Effect of temperature on LEDs?

High temp reduces efficiency/life; low temp generally improves performance.;

17.31 T5 more efficient than T8?

True (higher efficacy and compact size).;

17.32 Advantage of T5 lamps for design?

Smaller size → more compact, efficient luminaire designs.;

17.33 Why are high-watt CFLs alternatives to MH?

Good efficacy + better color rendering at lower wattage.;

17.34 Primary benefit of LED lighting?

High efficiency and long life (energy + maintenance savings).;

17.35 Can LEDs replace most sources?

True (in most applications LEDs outperform traditional sources).;

17.36 Important outdoor fixture characteristics?

Weatherproofing, durability, corrosion resistance, proper light distribution.;

17.37 When use asymmetrical outdoor fixtures?

For directional lighting (e.g., roadways, parking lots).;

17.38 How to reduce light pollution?

Use shielding, direct light downward, limit brightness and spill light.