Licensed Electrical Contractor Licensed Electrical Contractor Special Occupancies and Equipment Questions and Answers 2

Question 1

Per NEC Article 517, what is the maximum time permitted for the emergency system to restore power to life safety circuits in a hospital?

Accepted Answer

10 seconds

Answer

NEC 517.31 requires the emergency system to restore power to life safety branch circuits within 10 seconds of power interruption.

Question 2

Which NEC article governs the installation of electrical systems in hazardous (classified) locations involving flammable gases or vapors?

Accepted Answer

Article 500

Answer

NEC Article 500 covers the classification of hazardous locations where flammable gases, vapors, or combustible dusts may be present.

Question 3

When installing a swimming pool underwater luminaire operating at more than 15 volts, what is the minimum burial depth for a rigid metal conduit run from the forming shell to the junction box?

Accepted Answer

18 inches

Answer

NEC 680.23(F)(1) requires conduit runs from the forming shell to a deck box or junction box to be buried at least 18 inches below the deck surface.

Question 4

In a Class I, Division 1 hazardous location, which wiring method is generally required?

Accepted Answer

Threaded rigid metal conduit with explosion-proof fittings

Answer

NEC 501.10(A) requires threaded rigid metal conduit or threaded steel intermediate metal conduit with explosion-proof fittings in Class I, Division 1 locations.

Question 5

What is the minimum required height for overhead service conductors crossing a commercial parking lot subject to truck traffic?

Accepted Answer

18 feet

Answer

NEC 225.18 requires overhead conductors to maintain at least 18 feet of clearance over areas subject to truck traffic.

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Licensed Electrical Contractor Licensed Electrical Contractor Special Occupancies and Equipment Questions and Answers 2