CEA - Certified Electrical Apprentice NEC Wiring and Protection Questions and Answers — Questions and Answers
Question 1: According to NEC Table 310.16, what is the allowable ampacity for a 10 AWG THWN copper conductor in a raceway with not more than three current-carrying conductors in an ambient temperature of 30°C?
- 30A
- 40A
- 35A (Correct answer)
- 25A
Correct answer: 35A
NEC Table 310.16 specifies the allowable ampacities of insulated conductors. For a 10 AWG copper conductor with THWN insulation, which falls under the 75°C column, the ampacity is 35A.
Question 2: An apprentice is installing a 120V, 12A non-continuous, non-motor operated appliance that does not have an overcurrent protection rating marked on it. What is the maximum standard size overcurrent device that can be used for the branch circuit supplying only this appliance?
- 15A
- 20A (Correct answer)
- 25A
- 30A
Correct answer: 20A
According to NEC 422.11(E)(2), if a single non-motor operated appliance is rated at 13.3A or less and the overcurrent protection rating is not marked, the branch-circuit overcurrent device shall not exceed 20A.
Question 3: Which of the following locations in a dwelling unit requires GFCI protection for all 125-volt through 250-volt receptacles supplied by single-phase branch circuits rated 150 volts or less to ground?
- Hallways
- Bedrooms
- Closets
- Garages (Correct answer)
Correct answer: Garages
NEC Section 210.8(A) lists the locations in a dwelling unit that require GFCI protection for personnel. Garages and accessory buildings are explicitly included in this list for the specified receptacle types.
Question 4: To provide an effective ground-fault current path, metal parts of electrical raceways, enclosures, and equipment must be connected to establish electrical continuity and conductivity. What is this connection called?
- Grounding
- Isolating
- Bonding (Correct answer)
- Insulating
Correct answer: Bonding
The NEC Article 100 defines bonding as being "connected to establish electrical continuity and conductivity." Bonding ensures that all metallic parts are at the same electrical potential and provides a low-impedance path for fault current to facilitate the operation of overcurrent devices.
Question 5: An electrician is wiring an outdoor receptacle on the exterior of a commercial building. The area is exposed to rain. Which of the following wiring methods and materials is most appropriate for this wet location?
- Type NM cable in a standard PVC box
- Type THHN conductors in EMT with standard set-screw fittings
- Type XHHW conductors in Rigid Metal Conduit (RMC) with weatherproof fittings (Correct answer)
- Type MC cable with standard connectors
Correct answer: Type XHHW conductors in Rigid Metal Conduit (RMC) with weatherproof fittings
For wet locations, the NEC requires wiring methods and materials listed for such use. Rigid Metal Conduit (RMC) with weatherproof fittings provides robust protection against moisture. Conductors like XHHW are rated for wet locations. Other options like standard NM cable, EMT with standard fittings, or standard MC cable are not suitable for direct exposure to weather.
Question 6: When calculating the load for a branch circuit that supplies a continuous load, the circuit conductors must have an ampacity not less than what percentage of the continuous load, plus 100% of any noncontinuous load?
- 80%
- 100%
- 150%
- 125% (Correct answer)
Correct answer: 125%
NEC Section 210.19(A)(1) requires that branch-circuit conductors have an ampacity not less than 125% of the continuous loads, plus 100% of the noncontinuous loads. This is to account for the extra heat generated by loads that run for 3 hours or more.
CEA - Certified Electrical Apprentice NEC Wiring and Protection Questions and Answers
According to NEC Table 310.16, what is the allowable ampacity for a 10 AWG THWN copper conductor in a raceway with not more than three current-carrying conductors in an ambient temperature of 30°C?