NABCEP - Certified North American Board of Certified Energy Practitioners Specialist Electrical Component Inspection Questions and Answers — Questions and Answers
Question 1: During a visual inspection of a newly installed string inverter, which of the following findings would be the MOST immediate cause for concern and require correction before commissioning?
- The inverter's cooling fins are warm to the touch.
- A warning label for 'PHOTOVOLTAIC POWER SOURCE' is missing from a nearby DC conduit.
- There is less than the manufacturer-specified clearance for ventilation around the unit. (Correct answer)
- The DC input and AC output conduits are run parallel to each other for three feet.
Correct answer: There is less than the manufacturer-specified clearance for ventilation around the unit.
Inadequate clearance around an inverter can lead to overheating, which significantly reduces its efficiency and lifespan, and can cause a complete shutdown or failure. While missing labels and conduit routing are code violations that must be corrected, improper ventilation poses an immediate operational risk to the equipment itself.
Question 2: An inspector is examining the DC combiner box for a 600V nominal system. Which of the following observations is a clear violation of standard electrical practice and the NEC?
- The enclosure is made of a non-metallic, UV-rated material.
- The fuses are rated for 600V DC and sized at 156% of the string's short-circuit current (Isc).
- The equipment grounding conductor is bonded to the combiner box enclosure.
- Unused openings in the enclosure are sealed with duct tape. (Correct answer)
Correct answer: Unused openings in the enclosure are sealed with duct tape.
According to the National Electrical Code (NEC), all unused openings in electrical enclosures must be closed with listed plugs or plates to maintain the enclosure's integrity and environmental rating (e.g., NEMA 3R for outdoor use). Duct tape is not a listed or permanent solution and would be a violation.
Question 3: When inspecting exposed single-conductor cables (PV Wire/USE-2) within a rooftop solar array, what is a critical installation requirement according to NEC 690.31?
- Conductors must be supported at least every 10 feet.
- Conductors must be secured and supported to prevent damage from wind and abrasion. (Correct answer)
- Conductors must be enclosed in metallic conduit if they are within 1 foot of the roof surface.
- Conductors must be color-coded black for negative and red for positive for their entire length.
Correct answer: Conductors must be secured and supported to prevent damage from wind and abrasion.
NEC 690.31(C)(1) requires that exposed single conductors be supported and secured to prevent damage from wind, ice, and physical abrasion against the racking or roof surface. Proper wire management is crucial to prevent insulation breakdown, which could lead to ground faults or fires over the system's lifetime.
Question 4: A technician is inspecting a junction box on the back of a PV module and notices that the sealing gasket is cracked and displaced, with evidence of moisture ingress. What is the most likely consequence of this defect?
- An immediate increase in module open-circuit voltage (Voc).
- Corrosion of terminals and potential bypass diode failure. (Correct answer)
- A gradual discoloration of the module's front glass.
- The module's frame will lose its grounding connection.
Correct answer: Corrosion of terminals and potential bypass diode failure.
Moisture entering a junction box can cause corrosion on the electrical terminals and damage the bypass diodes. This can lead to increased resistance, heat buildup, reduced module output, and even create a fire hazard. The other options are not direct consequences of a compromised junction box seal.
Question 5: During a commissioning inspection, you are verifying the overcurrent protection for the inverter's AC output circuit. If the inverter's maximum continuous output current is 32A, what is the minimum standard size for the back-fed circuit breaker in the main panel, per NEC requirements?
- 30A
- 32A
- 40A (Correct answer)
- 50A
Correct answer: 40A
According to NEC 705.12(B) and 690.8(B), the overcurrent protection device for the inverter's output circuit must be sized to at least 125% of the maximum continuous output current. Therefore, 32A * 1.25 = 40A. This is a standard breaker size and is the minimum required.
Question 6: Which of the following must be verified during the inspection of a PV system's grounding and bonding system?
- All DC conductors are larger than the equipment grounding conductor.
- The grounding electrode conductor is routed in the same conduit as the AC output conductors.
- All metallic components that could become energized, such as module frames and racking, are bonded together and to the grounding system. (Correct answer)
- A separate grounding rod is installed for the PV array at the closest point to the inverter.
Correct answer: All metallic components that could become energized, such as module frames and racking, are bonded together and to the grounding system.
A fundamental safety requirement is to bond all exposed metallic parts of the system that could become energized (module frames, racking, enclosures) to the equipment grounding system. This creates a low-resistance path to ground, allowing overcurrent devices to operate and clear a fault, protecting personnel from shock hazards. While other grounding aspects are important, ensuring the bonding of all metallic components is a critical inspection point.
NABCEP - Certified North American Board of Certified Energy Practitioners Specialist Electrical Component Inspection Questions and Answers
During a visual inspection of a newly installed string inverter, which of the following findings would be the MOST immediate cause for concern and require correction before commissioning?