CEP Safety Standards & Compliance 3 — Questions and Answers
Question 1: According to OSHA 1910.333, what is the minimum approach distance for unqualified workers near exposed energized parts at 50V to 300V?
- They may approach with insulated gloves
- They must avoid contact but no specific distance is mandated (Correct answer)
- At least 3 feet
- They must not come closer than 10 feet
Correct answer: They must avoid contact but no specific distance is mandated
OSHA 1910.333 states unqualified workers must avoid contact with exposed energized parts at 50–300V; a minimum approach distance applies only to higher voltages for unqualified workers.
Question 2: What is the purpose of an Equipment Grounding Conductor (EGC) in a branch circuit?
- To carry normal load current back to the source
- To provide a low-impedance fault current path to operate overcurrent protection (Correct answer)
- To reduce electrical noise on sensitive equipment
- To serve as a neutral reference for single-phase loads
Correct answer: To provide a low-impedance fault current path to operate overcurrent protection
The EGC provides a low-impedance return path for fault current so that overcurrent protective devices operate quickly to clear the fault.
Question 3: Under NEC Article 210.8, GFCI protection is required for 125V, 15A and 20A receptacles in which of the following locations?
- Only in outdoor locations
- In bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens, and boathouses (Correct answer)
- Only in wet or damp locations
- Only in commercial and industrial occupancies
Correct answer: In bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens, and boathouses
NEC 210.8 mandates GFCI protection in numerous specific locations including bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens, and boathouses.
Question 4: Which arc flash boundary is defined as the distance at which an unprotected worker would receive a second-degree burn if an arc flash incident occurs?
- Restricted approach boundary
- Limited approach boundary
- Arc flash boundary (Correct answer)
- Prohibited approach boundary
Correct answer: Arc flash boundary
The arc flash boundary is the distance at which incident energy equals 1.2 cal/cm², the threshold for a just-curable second-degree burn.
Question 5: A facility has 480V switchgear with an available fault current of 65,000A. What critical characteristic must overcurrent protective devices in this equipment possess?
- A time-delay rating of at least 30 cycles
- A sufficient interrupting rating equal to or greater than 65,000A (Correct answer)
- A minimum 200A continuous current rating
- UL Listed for outdoor use
Correct answer: A sufficient interrupting rating equal to or greater than 65,000A
Per NEC 110.9, overcurrent protective devices must have an interrupting rating sufficient for the available fault current at their point of installation.
Question 6: What does NFPA 70E define as the 'prohibited approach boundary' for shock protection?
- The outer boundary where unqualified workers must stop
- The distance from energized parts where working is equivalent to making contact (Correct answer)
- The boundary requiring double insulated tools
- The zone requiring a second observer during work
Correct answer: The distance from energized parts where working is equivalent to making contact
The prohibited approach boundary is so close to exposed energized parts that working within it is considered the same as direct contact with those parts.
Question 7: Per NEC 700.12, emergency systems must have a power supply capable of operating within how many seconds of normal power failure?
- 30 seconds
- 10 seconds (Correct answer)
- 60 seconds
- 5 seconds
Correct answer: 10 seconds
NEC 700.12 requires emergency system power supplies to be capable of supplying power within 10 seconds of normal power failure.
CEP Safety Standards & Compliance 3
According to OSHA 1910.333, what is the minimum approach distance for unqualified workers near exposed energized parts at 50V to 300V?