Free Licensed Electrical Contractor Special Occupancies and Equipment Questions and Answers — Questions and Answers
Question 1: An electrician is installing an explosion-proof light fixture in a paint spray booth, which is classified as a Class I, Division 1 location. Which of the following wiring methods is permitted for connecting the fixture within this hazardous location?
- Type NM cable concealed in the wall.
- Electrical metallic tubing (EMT) with compression fittings.
- Threaded rigid metal conduit (RMC) with appropriate seals. (Correct answer)
- Type MC cable with a standard connector.
Correct answer: Threaded rigid metal conduit (RMC) with appropriate seals.
NEC Article 501.10(A)(1) specifies that in Class I, Division 1 locations, the only permitted wiring methods are threaded rigid metal conduit, threaded steel intermediate metal conduit, or Type MI cable with approved terminations. These methods are required to contain any potential explosion.
Question 2: According to NEC Article 680, what is the GFCI protection requirement for a single-phase, 240-volt motor for a permanently installed swimming pool?
- GFCI protection is required for all outlets supplying pool motors connected to single-phase, 120-volt through 240-volt branch circuits. (Correct answer)
- GFCI protection is not required if the motor is hardwired.
- GFCI protection is only required for 120-volt cord-and-plug-connected motors.
- GFCI protection is only required if the motor is located within 5 feet of the pool's edge.
Correct answer: GFCI protection is required for all outlets supplying pool motors connected to single-phase, 120-volt through 240-volt branch circuits.
NEC 680.21(C) requires that outlets supplying pool pump motors connected to single-phase, 120-volt through 240-volt branch circuits shall be provided with ground-fault circuit-interrupter protection for personnel. This applies whether the motor is connected by receptacle or by direct connection.
Question 3: In a hospital designated as a critical care (Category 1) space, which of the following loads would be required to be connected to the critical branch of the Essential Electrical System (EES)?
- The primary HVAC system for the building.
- Receptacles and fixed equipment in the operating room. (Correct answer)
- General hallway lighting.
- The hospital's main data processing center.
Correct answer: Receptacles and fixed equipment in the operating room.
According to NEC 517.33(A), the Critical Branch of the EES is designated to supply power for tasks and equipment essential for patient care during a power outage. This specifically includes receptacles, fixed equipment, and certain lighting in critical care areas like operating rooms and intensive care units.
Question 4: A contractor is installing four Level 2 Electric Vehicle Supply Equipment (EVSE) units in a commercial garage. Each unit has a maximum continuous rating of 32A at 240V. According to NEC Article 625, what is the calculated load for the feeder supplying these four units?
- 128A
- 102.4A
- 80A
- 160A (Correct answer)
Correct answer: 160A
NEC 625.41 and 625.42 state that EV charging loads shall be considered continuous loads. For both branch circuits and feeders, the load must be calculated at 125% of the maximum load. Therefore, the calculation is: 4 units * (32A * 1.25) = 4 * 40A = 160A.
Question 5: In a commercial major repair garage where service is performed on gasoline-powered vehicles, and assuming standard ventilation is not provided, how is the area from the floor up to a level of 18 inches above the floor classified?
- The area is unclassified.
- The area is a Class I, Division 2 location. (Correct answer)
- The area is a Class I, Division 1 location.
- The area is a Class II, Division 2 location.
Correct answer: The area is a Class I, Division 2 location.
NEC 511.3(C)(1)(b) states that for a major repair garage without the specified mechanical ventilation, the entire floor area is classified as a Class I, Division 2 location up to a level of 18 inches above the floor. This is because flammable gasoline vapors are heavier than air and can accumulate in this lower area.
Question 6: What is a primary requirement of a rapid shutdown system for a rooftop solar PV system, according to NEC Article 690.12, designed to enhance firefighter safety?
- To automatically disconnect the PV system from the utility grid during a power outage.
- To provide a local disconnect for individual solar panels for maintenance purposes.
- To reduce the voltage of controlled conductors OUTSIDE the array boundary to not more than 30 volts within 30 seconds of initiation. (Correct answer)
- To de-energize the service entrance conductors supplying the main building.
Correct answer: To reduce the voltage of controlled conductors OUTSIDE the array boundary to not more than 30 volts within 30 seconds of initiation.
The main purpose of PV rapid shutdown, as outlined in NEC 690.12, is to protect first responders. It requires that controlled conductors outside the array boundary (more than 1 ft from the array) be reduced to not more than 30 volts within 30 seconds of initiation. It also requires conductors inside the array boundary to be reduced to 80 volts within 30 seconds.
Free Licensed Electrical Contractor Special Occupancies and Equipment Questions and Answers
An electrician is installing an explosion-proof light fixture in a paint spray booth, which is classified as a Class I, Division 1 location.
Which of the following wiring methods is permitted for connecting the fixture within this hazardous location?