CEA Wiring Methods and Materials Questions and Answers — Questions and Answers
Question 1: According to the NEC, what is the required color code for the insulation of a grounded conductor (neutral) in a 120/240V system for conductors size 6 AWG or smaller?
- Green or green with a yellow stripe.
- Black, red, or blue.
- White or gray. (Correct answer)
- Any color other than white, gray, or green.
Correct answer: White or gray.
NEC Section 200.6(A) specifies that an insulated grounded conductor of 6 AWG or smaller shall be identified by a continuous white or gray outer finish. Green is reserved for equipment grounding conductors, while other colors like black, red, and blue are typically used for ungrounded (hot) conductors.
Question 2: An apprentice is installing a run of 1/2-inch Electrical Metallic Tubing (EMT) on a long, straight wall. According to the NEC, what is the maximum distance allowed between supports for this EMT run?
- 5 feet
- 8 feet
- 12 feet
- 10 feet (Correct answer)
Correct answer: 10 feet
NEC Section 358.30(A) requires that EMT be securely fastened in place at least every 10 feet. Additionally, it must be supported within 3 feet of each outlet box, junction box, device box, cabinet, or other tubing termination.
Question 3: An apprentice needs to select a cable for a residential branch circuit that will be run concealed within a dry, interior wall. Which of the following cable types is most commonly used and permitted for this application?
- Type UF (Underground Feeder)
- Type NM (Nonmetallic-Sheathed Cable) (Correct answer)
- Type SE (Service-Entrance Cable)
- Type TC (Tray Cable)
Correct answer: Type NM (Nonmetallic-Sheathed Cable)
NEC Article 334 permits the use of Type NM cable for both exposed and concealed work in normally dry locations, which makes it the standard for interior residential wiring. Type UF is for underground/direct burial, Type SE is primarily for service-entrance conductors, and Type TC is restricted to use in cable trays.
Question 4: An apprentice is laying out receptacle outlets for the living room of a new single-family dwelling. According to the NEC general provisions for receptacle placement along walls, no point measured horizontally along the floor line in any wall space should be more than how far from a receptacle outlet?
- 12 feet
- 4 feet
- 6 feet (Correct answer)
- 10 feet
Correct answer: 6 feet
NEC Section 210.52(A)(1) states that receptacles shall be installed so that no point measured horizontally along the floor line in any wall space is more than 6 feet from a receptacle outlet. This rule ensures that a standard 6-foot appliance cord can reach an outlet from any point along the wall, effectively placing receptacles a maximum of 12 feet apart.
Question 5: What is the primary purpose of the main bonding jumper in a service panel?
- To connect two separate service panels together.
- To provide a connection between the grounded service conductor (neutral) and the equipment grounding conductor(s). (Correct answer)
- To isolate the neutral bar from the panel enclosure.
- To connect the circuit breaker's trip unit to the busbar.
Correct answer: To provide a connection between the grounded service conductor (neutral) and the equipment grounding conductor(s).
The main bonding jumper provides the critical low-impedance path between the grounded conductor (neutral) and the equipment grounding conductor system at the service disconnect. This connection is essential for creating an effective ground-fault current path, which allows the overcurrent device (breaker or fuse) to operate quickly during a ground-fault.
Question 6: When installing Type NM cable in a new residential construction, which of the following is an NEC-compliant method for securing the cable?
- Draping the cable over ceiling joists without any fasteners.
- Within 12 inches of a single-gang nonmetallic box and every 4.5 feet thereafter. (Correct answer)
- Taping the cable directly to a water pipe.
- Within 6 inches of the panelboard cabinet and secured with a zip tie.
Correct answer: Within 12 inches of a single-gang nonmetallic box and every 4.5 feet thereafter.
NEC Section 334.30 requires Type NM cable to be secured by staples, listed cable ties, or similar fittings at intervals not exceeding 4.5 feet and within 12 inches of every outlet box, junction box, cabinet, or fitting. Securing cables to plumbing pipes is not permitted.
CEA Wiring Methods and Materials Questions and Answers
According to the NEC, what is the required color code for the insulation of a grounded conductor (neutral) in a 120/240V system for conductors size 6 AWG or smaller?