NEC Special Occupancies Questions and Answers — Questions and Answers
Question 1: An electrician is installing wiring in a Class I, Division 1 hazardous location. Which of the following wiring methods is generally permitted for this environment according to NEC Article 501?
- Electrical Metallic Tubing (EMT)
- Threaded rigid metal conduit (RMC) (Correct answer)
- Nonmetallic-sheathed cable (Type NM)
- Flexible metal conduit (FMC)
Correct answer: Threaded rigid metal conduit (RMC)
NEC Section 501.10(A) specifies the wiring methods permitted in Class I, Division 1 locations due to the continuous presence of flammable gases or vapors. Threaded rigid metal conduit (RMC) or threaded steel intermediate metal conduit (IMC) are primary methods listed because their construction and threaded connections are designed to contain an internal explosion and prevent it from igniting the surrounding hazardous atmosphere.
Question 2: In a commercial repair garage without adequate ventilation, what is the classification of the area up to 18 inches above the main floor, according to NEC Article 511?
- Class I, Division 1
- Unclassified
- Class II, Division 2
- Class I, Division 2 (Correct answer)
Correct answer: Class I, Division 2
According to NEC Section 511.3(C)(1)(b), in a major repair garage where ventilation is not provided, the area up to 18 inches above the floor is classified as a Class I, Division 2 hazardous location. This classification is due to the potential for flammable gasoline vapors, which are heavier than air, to accumulate near the floor in ignitable concentrations under abnormal conditions.
Question 3: What is the minimum number of receptacles required at each patient bed location in a general care area of a health care facility, as specified in NEC Article 517?
- Six
- Four
- Eight (Correct answer)
- Twelve
Correct answer: Eight
NEC Section 517.18(B) mandates that each patient bed location in a general care area be provided with a minimum of eight receptacles. This requirement was increased from four to eight in a previous code cycle to accommodate the growing number of electronic medical devices used for patient care. These receptacles must also be listed as "hospital grade."
Question 4: According to NEC Article 525, which of the following is required for all 125-volt, single-phase, 15- and 20-ampere non-locking-type receptacles readily accessible to the general public at a carnival?
- They must be protected by an arc-fault circuit-interrupter (AFCI).
- They must have ground-fault circuit-interrupter (GFCI) protection. (Correct answer)
- They must be installed in a locked enclosure.
- They must be supplied by a separately derived system.
Correct answer: They must have ground-fault circuit-interrupter (GFCI) protection.
NEC Section 525.23(A) requires that all 125-volt, single-phase, 15- and 20-ampere non-locking-type receptacles readily accessible to the general public or used for equipment disassembly/reassembly at carnivals, circuses, and fairs must be provided with GFCI protection for personnel.
Question 5: An electrician is installing receptacles near a permanently installed outdoor swimming pool at a private residence. According to NEC Article 680, all 125-volt, 15- and 20-ampere receptacles located within what distance of the inside walls of the pool must be GFCI protected?
- 10 feet
- 15 feet
- 25 feet
- 20 feet (Correct answer)
Correct answer: 20 feet
NEC Section 680.22(A)(4) requires that for other than storable pools, all 125-volt, 15- and 20-ampere receptacles located within 20 feet of the inside walls of the pool must be protected by a ground-fault circuit-interrupter (GFCI).
Question 6: In an agricultural building housing livestock, an equipotential plane is installed in a concrete confinement area. According to NEC Article 547, what is the primary purpose of bonding this plane to the electrical grounding system?
- To serve as the primary equipment grounding conductor for the building.
- To prevent a difference in voltage from developing within the plane and between conductive surfaces. (Correct answer)
- To provide a dedicated path for lightning protection.
- To reduce harmonic distortion from variable frequency drives.
Correct answer: To prevent a difference in voltage from developing within the plane and between conductive surfaces.
As stated in the definition in NEC 547.2 and the requirements in 547.10, an equipotential plane is connected to the electrical grounding system to prevent a difference in voltage from developing within the plane. This bonding minimizes any potential difference between conductive surfaces (e.g., the concrete floor, metal stanchions, waterers) that livestock can touch, thereby protecting the animals from stray voltage (tingle voltage).
NEC Special Occupancies Questions and Answers
An electrician is installing wiring in a Class I, Division 1 hazardous location.
Which of the following wiring methods is generally permitted for this environment according to NEC Article 501?