Electrical Component Inspection Flashcards
7 cards from real NABCEP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Component Inspection flashcards as text
During inspection of a battery-based PV system, you find that the battery bank negative terminal is directly bonded to the equipment grounding conductor at the charge controller. According to NEC Article 690, what type of system is this?
Answer: A solidly grounded DC system
A solidly grounded DC system has one conductor of the circuit directly connected to the grounding electrode system without any impedance.
An inspector observes that a string of 10 modules in series produces 380V Voc at STC but only 310V during morning inspection. What is the most likely cause?
Answer: The system has a partial shading condition or failed module
A significantly lower-than-expected string Voc during clear conditions typically indicates a failed module or partial shading that reduces voltage contribution from part of the string.
During a thermal imaging inspection of PV modules, you identify a cell-level hot spot that is 40°C above surrounding cells. What is the most probable root cause?
Answer: A cracked or degraded cell with increased series resistance
Cell-level hot spots indicate locally increased resistance, most commonly from cracked cells, delamination, or soiling that causes current to flow through a high-resistance path.
An inspector finds that the service entrance panel where the PV system interconnects has a main breaker rated at 200A and the bus bar is also rated at 200A. The PV interconnection breaker is 40A. Does this installation comply with NEC 705.12(B)(2)?
Answer: No, the PV breaker must be located at the opposite end from the main breaker
NEC 705.12(B)(2) requires the PV supply-side breaker to be at the opposite end of the bus from the main breaker when using the 120% rule, to limit worst-case bus loading.
During inspection, you measure insulation resistance of a PV array using a megohmmeter and find a reading of 0.5 MΩ between the positive conductor and ground. What does this indicate?
Answer: Significant insulation degradation requiring further investigation
A megohmmeter reading of 0.5 MΩ is far below the minimum acceptable insulation resistance (typically ≥1 MΩ for PV systems), indicating compromised insulation that must be investigated.
A PV system inspection reveals that USE-2 conductors are used for the module inter-string wiring inside the junction box. Is this installation correct?
Answer: No, PV wire or THWN-2 must be used inside junction boxes
USE-2 cable is approved for outdoor exposed wiring between modules but is not listed for use inside enclosures or raceways; PV wire or THWN-2 is required inside junction boxes.
During commissioning, an inspector verifies that a grid-tied inverter's anti-islanding protection is functional by simulating a utility outage. The inverter fails to disconnect within 2 seconds. What is the safety significance?
Answer: The energized conductors could pose an electrocution hazard to utility workers
Failed anti-islanding protection means the inverter continues to energize utility conductors after grid disconnect, creating an electrocution hazard for utility lineworkers who assume conductors are de-energized.