Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsEasy
A client requests a new 240-volt, 30-amp circuit for an electric vehicle charging station in their attached garage. The circuit will originate from the main service panel. Which type of cable is generally NOT permitted for this application within the wall cavities of a residential building, according to the NEC?
- AType SE cable
- BType NM-B cable
- CType UF cable
- DType MC cable
Show answer & explanationAnswer & explanation
Correct answer: C. Type UF cable
Type UF (Underground Feeder) cable is primarily designed for direct burial and wet locations, and while it can be used indoors, it is generally not the most common or preferred choice for concealed wiring in dry, residential wall cavities due to its robust, round construction which can be harder to install and terminate than flat NM-B. NM-B, SE, and MC are all commonly permitted for such indoor installations.
Why the other options are wrong
- A. Permitted. Type SE (Service Entrance) cable can be used as a branch circuit or feeder in residential applications.
- B. Permitted. Type NM-B (Romex) is the most common cable for concealed wiring in dry locations in residential structures.
- D. Permitted. Type MC (Metal-Clad) cable is suitable for use in dry locations and can be concealed in walls.
Residential Wiring Methods
The NEC specifies various wiring methods and materials suitable for different applications in residential buildings, considering location (dry/wet, exposed/concealed) and protection.
- Type NM-B is the most common for dry, concealed residential wiring.
- Type UF is primarily for direct burial and wet locations.
- Type SE and Type MC cables have broader applications, including residential interiors.
- Choosing the correct cable type is crucial for safety and code compliance.
Memory trick: Every home has a 'N-U-M' of cables, but only some fit in the wall!