Construction Electrical Systems in Construction 2 — Questions and Answers
Question 1: What is the purpose of a load center (electrical panel) in a building?
- To step down utility voltage to usable levels
- To distribute electrical power to branch circuits and provide overcurrent protection (Correct answer)
- To convert AC power to DC power for appliances
- To monitor and record electrical usage for billing
Correct answer: To distribute electrical power to branch circuits and provide overcurrent protection
A load center distributes incoming electrical service into individual branch circuits, each protected by a breaker or fuse to prevent overloads.
Question 2: When pulling wire through conduit, what material is commonly used to reduce friction?
- Motor oil
- Wire pulling lubricant (wire pulling gel) (Correct answer)
- WD-40
- Silicone spray
Correct answer: Wire pulling lubricant (wire pulling gel)
Wire pulling lubricant (pulling gel) is specifically designed to reduce friction without damaging wire insulation and is the industry-standard choice.
Question 3: What is the minimum clearance required between the top of a residential electrical panel and the ceiling?
- 3 feet
- 6 feet
- No minimum required
- 6.5 feet (Correct answer)
Correct answer: 6.5 feet
NEC 110.26 requires a minimum dedicated headroom of 6.5 feet (78 inches) above electrical equipment to ensure safe working space.
Question 4: What does the term 'ampacity' refer to in electrical construction?
- The voltage capacity of a conductor
- The maximum current a conductor can carry continuously without exceeding its temperature rating (Correct answer)
- The total wattage a circuit can handle
- The resistance of a conductor per foot
Correct answer: The maximum current a conductor can carry continuously without exceeding its temperature rating
Ampacity is the maximum current in amperes a conductor can continuously carry under specific conditions without exceeding its insulation temperature rating.
Question 5: Which AWG wire size is commonly used for a 20-amp, 120-volt branch circuit?
- 14 AWG
- 12 AWG (Correct answer)
- 10 AWG
- 8 AWG
Correct answer: 12 AWG
12 AWG copper wire has an ampacity of 20 amps and is the NEC-required minimum size for 20-amp branch circuits.
Question 6: What is a 'home run' in electrical construction terminology?
- The main service entrance cable from the utility
- The cable that runs from the last device on a circuit back to the panel (Correct answer)
- The feeder from the panel to a subpanel
- The ground wire routed to the grounding electrode system
Correct answer: The cable that runs from the last device on a circuit back to the panel
A home run is the wire or cable that connects the last outlet or device on a circuit directly back to the main panel, completing the circuit path.
Question 7: Under OSHA 1926 Subpart K, what is the required assured equipment grounding conductor program (AEGCP) used as an alternative to?
- Lockout/Tagout procedures
- GFCI protection on construction sites (Correct answer)
- Arc flash labeling requirements
- Low-voltage equipment exemptions
Correct answer: GFCI protection on construction sites
OSHA 1926.404 allows an assured equipment grounding conductor program as an alternative to GFCI protection for temporary power on construction sites.
Construction Electrical Systems in Construction 2
What is the purpose of a load center (electrical panel) in a building?