EETC Wiring Methods 5

Question 1

Which wiring method is specifically prohibited in ducts, plenums, or other air-handling spaces unless it is specifically listed for plenum use?

Accepted Answer

Type NM-B cable

Answer

NEC 300.22 prohibits Type NM-B cable in ducts or plenums because it is not listed for plenum use and produces toxic gases when burned.

Question 2

What is the maximum trade size for electrical nonmetallic tubing (ENT) permitted by the NEC?

Accepted Answer

3 inches

Answer

NEC 362.20 limits ENT to a maximum trade size of 2 inches; larger sizes are not listed or manufactured for ENT.

Question 3

In a concealed knob-and-tube wiring system found in older construction, what is prohibited from being done without special approval?

Accepted Answer

Insulating over the wiring with thermal insulation

Answer

NEC 394.12 prohibits covering knob-and-tube wiring with thermal insulation because it depends on open-air cooling and insulation causes overheating.

Question 4

What is the purpose of an expansion fitting (expansion joint) in a conduit installation?

Accepted Answer

To compensate for thermal expansion and contraction

Answer

Expansion fittings accommodate the linear expansion and contraction of conduit due to temperature changes, preventing stress on the system.

Question 5

When using surface metal raceways (Type 386), what is the primary NEC concern regarding splices?

Accepted Answer

Splices must only be made at listed splice boxes or fittings

Answer

NEC 386.56 permits splices in surface metal raceways only at listed junction boxes or fittings designed for that purpose.

(EETC) Electrical Technician Certification Practice Test