PC - Professional Electrical Contractor Special Occupancies and Equipment Questions and Answers 1 — Questions and Answers
Question 1: According to NEC Article 680, what is the minimum requirement for equipotential bonding of the perimeter surface of a permanently installed swimming pool?
- A #8 AWG solid copper conductor buried 12-18 inches deep, 12-18 inches from the inside wall.
- A #6 AWG stranded copper conductor in conduit placed 24-30 inches from the inside wall.
- A #8 AWG solid copper conductor secured within or under the perimeter surface 4-6 inches below subgrade, 18-24 inches from the inside walls. (Correct answer)
- A #6 AWG solid aluminum conductor buried 6-8 inches deep, 36 inches from the inside wall.
Correct answer: A #8 AWG solid copper conductor secured within or under the perimeter surface 4-6 inches below subgrade, 18-24 inches from the inside walls.
NEC 680.26(B)(2)(b) specifies that for alternate means of equipotential bonding (like when nonconductive pool shells are used), a bare solid copper conductor, not smaller than 8 AWG, shall be installed. It must be secured within or under the perimeter surface, 4 to 6 inches below the subgrade, and positioned 18 to 24 inches from the inside walls of the pool.
Question 2: A contractor is installing electrical systems in a new hospital's operating room, which is a Category 1 space. Which branches are required for the Essential Electrical System (EES) in this area?
- Life Safety and Critical branches only.
- Life Safety, Critical, and Equipment branches. (Correct answer)
- Emergency and Standby branches.
- Normal Power and an Optional Standby System.
Correct answer: Life Safety, Critical, and Equipment branches.
According to NEC Article 517, a Type 1 Essential Electrical System (EES) is required for healthcare facilities with Category 1 spaces where failure of the electrical system is likely to cause major injury or death. A Type 1 EES consists of three separate branches: Life Safety, Critical, and Equipment.
Question 3: In a hazardous location classified as Class I, Division 1, what is the primary concern that dictates the wiring methods and equipment used?
- The presence of combustible dust during normal operation.
- The presence of easily ignitable fibers or flyings.
- The presence of flammable gases or vapors under abnormal conditions.
- The presence of flammable gases or vapors is expected under normal operating conditions. (Correct answer)
Correct answer: The presence of flammable gases or vapors is expected under normal operating conditions.
NEC Article 500 defines a Class I, Division 1 location as an area where ignitible concentrations of flammable gases or vapors can exist under normal operating conditions. This high probability of a hazardous atmosphere necessitates the most stringent wiring and equipment protection methods to prevent ignition.
Question 4: For a solar photovoltaic (PV) system installed on a building, what are the requirements for rapid shutdown for controlled conductors located MORE than 3 feet from the point of entry inside the building?
- They must be limited to not more than 80 volts within 60 seconds of shutdown initiation.
- They must be de-energized to 0 volts within 10 seconds of shutdown initiation.
- They are not subject to rapid shutdown requirements.
- They must be limited to not more than 30 volts within 30 seconds of shutdown initiation. (Correct answer)
Correct answer: They must be limited to not more than 30 volts within 30 seconds of shutdown initiation.
NEC 690.12 specifies the requirements for the rapid shutdown of PV systems on buildings to reduce shock hazards for emergency responders. For controlled conductors located outside the array boundary or more than 3 feet from the point of entry into the building, the voltage must be limited to not more than 30 volts within 30 seconds of initiating the rapid shutdown.
Question 5: Which of the following wiring methods is generally NOT permitted for wiring within an elevator hoistway, according to NEC Article 620?
- Rigid metal conduit (RMC).
- Electrical metallic tubing (EMT).
- Type NM (Nonmetallic-sheathed) cable. (Correct answer)
- Intermediate metal conduit (IMC).
Correct answer: Type NM (Nonmetallic-sheathed) cable.
NEC Article 620 specifies acceptable wiring methods for elevators, hoistways, and machine rooms. Permitted methods include robust options like RMC, IMC, and EMT. Type NM cable is generally prohibited in these locations due to lack of physical protection and specific flame-retardant characteristics required for these environments.
Question 6: In a patient care space of a health care facility, branch circuits must be installed using a method that provides an effective ground-fault current path. Which of the following meets this requirement per NEC Article 517?
- Type NM cable with an equipment grounding conductor.
- A metal raceway or a cable with a metallic armor or sheath. (Correct answer)
- PVC conduit with an insulated copper equipment grounding conductor.
- Direct-burial cable run concealed in the wall.
Correct answer: A metal raceway or a cable with a metallic armor or sheath.
NEC 517.13(A) requires that branch circuits serving patient care spaces be installed in a metal raceway or be a cable assembly with a metallic armor or sheath, such as Type MC or AC cable. This is to ensure a redundant and reliable equipment grounding path to minimize electrical hazards to patients.
PC - Professional Electrical Contractor Special Occupancies and Equipment Questions and Answers 1
According to NEC Article 680, what is the minimum requirement for equipotential bonding of the perimeter surface of a permanently installed swimming pool?