Licensed Electrical Contractor Special Occupancies and Equipment Questions and Answers — Questions and Answers
Question 1: For a legally required emergency system, what is the maximum time permitted by NEC 700.12 for the emergency power source to be connected to the load after a normal power failure?
- 10 seconds (Correct answer)
- 60 seconds
- 2 minutes
- Immediately, with no interruption
Correct answer: 10 seconds
NEC 700.12 requires that emergency systems have power available within a maximum of 10 seconds after the interruption of the normal supply. This ensures that critical life safety systems, such as egress lighting and fire alarms, are restored quickly.
Question 2: A 2-inch rigid metal conduit leaves a Class I, Division 1 hazardous location and enters an unclassified area. According to NEC 501.15(A)(4), where must the sealing fitting be located relative to the boundary?
- On the hazardous side of the boundary only, within 18 inches.
- On either side of the boundary, as close as practicable but no more than 10 feet from the boundary. (Correct answer)
- Exactly at the boundary wall, with the fitting half in each area.
- Only in the unclassified area, within 24 inches of the boundary.
Correct answer: On either side of the boundary, as close as practicable but no more than 10 feet from the boundary.
NEC 501.15(A)(4) requires a seal in each conduit run passing from a Class I, Division 1 location into an unclassified location. The sealing fitting is permitted to be installed on either side of the boundary within 10 feet of it and must be designed to minimize the passage of gases or vapors.
Question 3: Which of the following components is NOT required by NEC 680.26(B) to be bonded to the equipotential bonding grid for a permanently installed swimming pool?
- Metal shells of underwater luminaires.
- The reinforcing steel of the pool shell.
- A metal drinking fountain located 8 feet from the inside wall of the pool. (Correct answer)
- Metal-sheathed cables and metal raceways within 5 feet horizontally of the inside walls of the pool.
Correct answer: A metal drinking fountain located 8 feet from the inside wall of the pool.
NEC 680.26(B) requires the bonding of various conductive parts. Specifically, 680.26(B)(7) requires bonding of all fixed metal parts within 5 feet horizontally of the inside walls of the pool. Since the metal drinking fountain is located 8 feet away, it is outside this specified bonding perimeter and is not required to be part of the equipotential grid.
Question 4: In a patient care vicinity of a hospital designated as a 'critical care (Category 1) space', which of the following is a specific requirement for branch circuits serving patient-care-related electrical equipment?
- They must be supplied by an isolated power system.
- All receptacles must be of a twist-lock type.
- The wiring method must be Type MI cable exclusively.
- They must be wired with an insulated copper equipment grounding conductor in addition to the metal raceway. (Correct answer)
Correct answer: They must be wired with an insulated copper equipment grounding conductor in addition to the metal raceway.
NEC 517.13(A) and (B) mandate that in critical care spaces, branch circuits must be installed in a metal raceway or metal-sheathed cable that provides an effective ground-fault current path. In addition, an insulated copper equipment grounding conductor must be installed with the circuit conductors, creating a redundant grounding system for enhanced patient safety.
Question 5: According to NEC Article 625, what type of personnel protection is required for all 120-volt, single-phase, 15- and 20-ampere receptacles installed for the connection of electric vehicle charging equipment?
- An arc-fault circuit interrupter (AFCI) device.
- A ground-fault circuit-interrupter (GFCI) for personnel. (Correct answer)
- A system that monitors the charging cable and interrupts the circuit on a fault.
- No special protection is required beyond a standard overcurrent device.
Correct answer: A ground-fault circuit-interrupter (GFCI) for personnel.
NEC 625.54 requires that all single-phase receptacles rated 150 volts to ground or less, and 50 amperes or less, installed for the connection of electric vehicle charging, must have ground-fault circuit-interrupter (GFCI) protection for personnel. This is in addition to other GFCI requirements found in Article 210.
Question 6: A contractor is wiring a new concrete-floor dairy barn where livestock will be confined. To mitigate the effects of stray voltage, what does NEC Article 547 require to be installed in the concrete floor?
- A dedicated isolated grounding system for all electrical equipment.
- Type UF cable embedded directly in the concrete for all circuits.
- An equipotential plane bonded to the building's grounding electrode system. (Correct answer)
- A ground-fault circuit interrupter for every 120V receptacle.
Correct answer: An equipotential plane bonded to the building's grounding electrode system.
NEC 547.10 requires that an equipotential plane be installed in concrete floors of animal confinement areas. This plane, typically wire mesh or rebar, is bonded to the electrical grounding system to keep all conductive surfaces at the same electrical potential, protecting sensitive livestock from stray voltage.
Licensed Electrical Contractor Special Occupancies and Equipment Questions and Answers
For a legally required emergency system, what is the maximum time permitted by NEC 700.12 for the emergency power source to be connected to the load after a normal power failure?