NEC Special Occupancies 3

Question 1

In a Class I, Division 1 location, a conduit seal entering an explosionproof enclosure that contains arcing devices must be installed within what distance of the enclosure?

Accepted Answer

18 inches

Answer

NEC 501.15(A)(1) requires the seal fitting to be within 18 in. of the enclosure.

Question 2

Which hazardous material defines a Class II location?

Accepted Answer

Combustible dust

Answer

Class II locations are hazardous because of combustible dust (NEC 500.5(C)).

Question 3

A textile mill where cotton lint is handled but not likely to be suspended in the air in ignitible quantities is classified as what?

Accepted Answer

Class III

Answer

Ignitible fibers and flyings make a location Class III (NEC 500.5(D)).

Question 4

In the Zone classification system, which zone has ignitible concentrations of flammable gases or vapors present continuously or for long periods?

Accepted Answer

Zone 0

Answer

NEC 505.5(B)(1) defines Zone 0 as continuous or long-term presence of ignitible concentrations.

Question 5

Threaded rigid metal conduit connections in Class I, Division 1 locations must have at least how many fully engaged threads?

Accepted Answer

5 threads

Answer

NEC 500.8(E) requires at least five full threads fully engaged for NPT threaded entries.

NEC Practice Test

NEC Practice Test

NEC Special Occupancies 3