CEP Safety Standards & Compliance 5 — Questions and Answers
Question 1: Which NEC section requires arc-fault circuit interrupter (AFCI) protection for branch circuits supplying outlets in dwelling unit bedrooms?
- NEC 210.8
- NEC 210.12 (Correct answer)
- NEC 230.95
- NEC 215.9
Correct answer: NEC 210.12
NEC 210.12 requires AFCI protection for branch circuits supplying outlets in bedrooms and, in recent editions, most living spaces of dwelling units.
Question 2: What is the significance of the 'available fault current' calculation when designing an electrical system?
- It determines the load calculation for service sizing
- It ensures that all overcurrent devices are rated to interrupt the maximum possible short-circuit current (Correct answer)
- It sets the minimum conductor insulation voltage rating
- It establishes the grounding electrode conductor size
Correct answer: It ensures that all overcurrent devices are rated to interrupt the maximum possible short-circuit current
Available fault current calculations ensure that every overcurrent protective device has sufficient interrupting capacity to safely clear a bolted short-circuit fault without catastrophic failure.
Question 3: According to NFPA 70B, what is the recommended frequency for thermographic (infrared) inspections of electrical switchgear in industrial facilities?
- Every 5 years under normal conditions
- Annually, or more frequently in harsh environments (Correct answer)
- Only after a fault event or equipment failure
- Every 10 years per the NEC maintenance schedule
Correct answer: Annually, or more frequently in harsh environments
NFPA 70B recommends annual thermographic inspections of electrical equipment, with more frequent inspections in harsh or high-duty-cycle environments.
Question 4: Under NEC Article 430, what is the maximum allowable size of an inverse time circuit breaker used as the branch-circuit short-circuit and ground-fault protective device for a motor with a full-load current of 20A?
- 40A
- 250% of FLA = 50A (Correct answer)
- 125% of FLA = 25A
- 175% of FLA = 35A
Correct answer: 250% of FLA = 50A
NEC 430.52 Table allows an inverse time circuit breaker to be sized up to 250% of motor full-load amperes for short-circuit protection, giving a maximum of 50A for a 20A FLA motor.
Question 5: What is the purpose of the 'flash hazard analysis' or incident energy analysis required by NFPA 70E?
- To determine if equipment needs to be replaced
- To calculate the incident energy at a worker's face and hands so appropriate PPE can be selected (Correct answer)
- To identify leakage current on equipment chassis
- To calculate the short-circuit current for breaker sizing
Correct answer: To calculate the incident energy at a worker's face and hands so appropriate PPE can be selected
The incident energy analysis calculates the thermal energy released at a working distance during an arcing fault so that PPE with a sufficient arc rating can be selected to protect the worker.
Question 6: Per NEC 250.122, what factor primarily determines the minimum size of an equipment grounding conductor?
- The length of the circuit run
- The ampere rating of the overcurrent protective device protecting the circuit (Correct answer)
- The voltage of the circuit
- The type of insulation on the phase conductors
Correct answer: The ampere rating of the overcurrent protective device protecting the circuit
NEC Table 250.122 sizes the EGC based on the rating of the overcurrent device protecting the circuit, ensuring the EGC can carry fault current long enough for the device to operate.
Question 7: Which OSHA standard requires employers to establish, implement, and enforce an electrical safety program for employees who work on or near electrical hazards?
- OSHA 1910.137
- OSHA 1910.331–.335 (Correct answer)
- OSHA 1910.147
- OSHA 1926.50
Correct answer: OSHA 1910.331–.335
OSHA 1910.331–.335 (Electrical Safety-Related Work Practices) requires employers to establish safety programs covering training, work procedures, and protective equipment for employees exposed to electrical hazards.
CEP Safety Standards & Compliance 5
Which NEC section requires arc-fault circuit interrupter (AFCI) protection for branch circuits supplying outlets in dwelling unit bedrooms?