CEM Lighting Systems 3 — Questions and Answers
Question 1: Which lamp type produces light through an electrical discharge in a gas-filled tube without a filament, making it suitable for cold storage facilities?
- Incandescent
- Halogen
- Fluorescent (Correct answer)
- High-pressure sodium
Correct answer: Fluorescent
Fluorescent lamps use electrical discharge through mercury vapor and phosphor coating, though performance can decrease in very cold temperatures.
Question 2: In a lighting retrofit economic analysis, simple payback period is calculated as:
- Annual energy savings ÷ installation cost
- Installation cost ÷ annual energy savings (Correct answer)
- Installation cost × annual energy savings
- Annual energy savings × project life
Correct answer: Installation cost ÷ annual energy savings
Simple payback = Initial cost / Annual savings, giving the number of years to recover the investment.
Question 3: What is the primary advantage of occupancy sensors in private offices compared to open-plan areas?
- Higher dimming resolution
- Greater energy savings due to predictable single-occupant patterns (Correct answer)
- Compatibility with daylight harvesting
- Lower installation cost per sensor
Correct answer: Greater energy savings due to predictable single-occupant patterns
Private offices have predictable vacancy periods, allowing occupancy sensors to turn lights off completely when the occupant is absent, yielding larger savings.
Question 4: Ballast factor (BF) greater than 1.0 for a fluorescent ballast indicates:
- The ballast operates at reduced lamp output
- The ballast drives the lamp above rated lumen output (Correct answer)
- The ballast has higher power factor
- The ballast reduces harmonic distortion
Correct answer: The ballast drives the lamp above rated lumen output
A BF > 1.0 means the ballast drives the lamp to produce more lumens than the rated (reference ballast) value.
Question 5: A parking garage uses 175W HID fixtures running 4,000 hours/year at $0.12/kWh. Replacing with 60W LED fixtures saves how much annually per fixture?
- $47.00
- $55.20 (Correct answer)
- $27.60
- $36.00
Correct answer: $55.20
Savings = (175-60)W × 4,000h / 1,000 × $0.12 = 115 × 4 × 0.12 = $55.20 per fixture annually.
Question 6: Which IES illuminance category is typically recommended for fine detail assembly tasks requiring high visual acuity?
- Category A (3–5 fc)
- Category C (10–20 fc)
- Category E (50–100 fc) (Correct answer)
- Category G (1000–2000 fc)
Correct answer: Category E (50–100 fc)
IES Category E (50–100 fc) is specified for tasks with fine details where visual performance is critical.
Question 7: Power factor correction in lighting systems is important because:
- It increases lamp lumen output
- It reduces reactive power demand and utility penalties (Correct answer)
- It extends lamp life by reducing voltage spikes
- It improves color rendering index
Correct answer: It reduces reactive power demand and utility penalties
Correcting power factor minimizes reactive (non-working) power, reducing utility demand charges and distribution losses.
CEM Lighting Systems 3
Which lamp type produces light through an electrical discharge in a gas-filled tube without a filament, making it suitable for cold storage facilities?