Electrical Systems in Buildings Flashcards
6 cards from real Building Engineering practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Electrical Systems in Buildings flashcards as text
What NEC article primarily governs the installation of emergency lighting systems in commercial buildings?
Answer: Article 700
NEC Article 700 covers emergency systems that supply illumination and power when normal power fails in occupancies required by code.
Which type of transformer is typically used to step down 480V three-phase to 208/120V in a commercial building?
Answer: Dry-type step-down transformer
Dry-type step-down transformers are standard in commercial buildings for converting 480V distribution voltage to usable 208/120V service.
What is meant by 'demand factor' in building electrical load calculations?
Answer: The ratio of maximum demand to total connected load
Demand factor accounts for the fact that not all connected electrical loads operate simultaneously at full capacity, allowing smaller service sizing.
Which grounding electrode is required by NEC for all new building construction?
Answer: Concrete-encased electrode (Ufer ground)
NEC requires a concrete-encased electrode (Ufer ground) in new construction because reinforcing steel embedded in concrete provides an excellent low-resistance ground.
What is the purpose of a power quality meter installed on a building's electrical system?
Answer: To monitor voltage, current, harmonics, and power factor continuously
A power quality meter provides real-time and historical data on voltage sags, harmonics, power factor, and demand to identify efficiency issues.
At what maximum height above grade must exterior building lighting circuits with branch circuit wiring be protected by RMC or IMC per NEC?
Answer: 8 feet
NEC requires physical protection to at least 8 feet above grade for conductors exposed to physical damage in exterior applications.