Master Electrician Exam (NEC)Special Occupancies, Equipment, and ConditionsHard
A master electrician is installing lighting fixtures in an agricultural building that houses livestock and has a corrosive atmosphere due to animal waste. According to NEC Article 547, which of the following statements regarding the wiring methods is correct?
- ANonmetallic boxes and enclosures are prohibited in agricultural buildings due to lack of mechanical strength.
- BType UF (underground feeder) cable is permitted to be installed exposed or concealed, provided it is protected from physical damage.
- CAll wiring methods must be listed for use in hazardous (classified) locations due to the corrosive atmosphere.
- DType NMC (nonmetallic-sheathed cable, corrosion-resistant) is permitted if installed exposed and secured to the surface.
Show answer & explanationAnswer & explanation
Correct answer: B. Type UF (underground feeder) cable is permitted to be installed exposed or concealed, provided it is protected from physical damage.
NEC 547.5(A)(1) allows Type UF cable to be installed exposed or concealed, provided it is protected from physical damage, in agricultural buildings with corrosive atmospheres. It is suitable for wet and corrosive conditions.
Why the other options are wrong
- A. Nonmetallic boxes and enclosures are often preferred in corrosive atmospheres to resist corrosion and are permitted if listed for the application (547.5(C)).
- C. Corrosive atmospheres in agricultural buildings are typically not classified as hazardous (explosive) locations, so hazardous location wiring methods are not generally required unless other factors dictate it.
- D. While NMC has a corrosion-resistant jacket, it is not listed in 547.5 as a permitted wiring method for corrosive atmospheres in agricultural buildings.
Agricultural Building Wiring (NEC)
Electrical installations in agricultural buildings, especially those housing livestock, have specific NEC requirements under Article 547 to address corrosive atmospheres, dust, and damp conditions, often permitting robust wiring methods like Type UF cable.
- Addresses corrosive, damp, and dusty environments.
- Specific wiring methods like Type UF cable are permitted.
- Nonmetallic boxes and enclosures are often preferred.
- Equipment must be listed for the conditions.
Memory trick: Farm Wiring: Corrosive air, so use tough UF cable or non-metal boxes.