NABCEP Electrical Component Inspection 2 — Questions and Answers
Question 1: During a PV system inspection, you notice the output circuit conductors are routed through metal conduit with no separation from the grounding electrode conductor. What is the primary concern?
- Voltage drop will increase significantly
- Induced currents may cause heating in the metallic conduit (Correct answer)
- The grounding electrode conductor must always be in PVC
- No concern exists as long as the conduit is bonded
Correct answer: Induced currents may cause heating in the metallic conduit
Routing current-carrying conductors through metal conduit without including the return conductor can induce eddy currents in the conduit, causing heating.
Question 2: A technician inspects a string inverter and finds the DC input voltage is 15% above the inverter's maximum rated input voltage. What is the most likely cause?
- Modules are operating at STC temperature
- Ambient temperature is unusually low, increasing Voc (Correct answer)
- The inverter MPPT range is too narrow
- The array is undersized for the inverter
Correct answer: Ambient temperature is unusually low, increasing Voc
Cold temperatures increase PV module open-circuit voltage (Voc), which can exceed inverter maximum DC input ratings if temperature correction was not applied during design.
Question 3: When inspecting a ground-mounted PV array, you observe rust staining on the mounting rails below the module clamps. What does this most likely indicate?
- The modules are generating excessive heat
- Galvanic corrosion between dissimilar metals at the clamp interface (Correct answer)
- The array has been exposed to excessive UV radiation
- The clamps are overtorqued causing metal fatigue
Correct answer: Galvanic corrosion between dissimilar metals at the clamp interface
Rust staining at clamp interfaces typically indicates galvanic corrosion caused by contact between dissimilar metals such as aluminum rails and steel fasteners without proper isolation.
Question 4: An inspector finds that the AC disconnect is labeled with a voltage rating of 240V but is installed on a 208V three-phase system. What is the appropriate finding?
- This is acceptable since 240V exceeds 208V (Correct answer)
- The disconnect must be replaced with a 208V-rated unit
- The disconnect is acceptable only if it is OCPD-rated
- The disconnect voltage rating must exactly match system voltage
Correct answer: This is acceptable since 240V exceeds 208V
Electrical equipment may be used at voltages at or below its voltage rating; a 240V-rated disconnect is acceptable on a 208V system.
Question 5: During a commissioning inspection, you identify that the PV source circuit fuses are rated at 20A but the module's maximum series fuse rating (Isc × 1.25 × 1.25) calculates to 15A. What action is required?
- No action needed if the wire is rated for 20A
- Replace the fuses with properly sized 15A fuses (Correct answer)
- Add a parallel bypass diode to each module
- Increase the number of modules in the string
Correct answer: Replace the fuses with properly sized 15A fuses
Overcurrent protection devices must not exceed the module's maximum series fuse rating to protect module wiring and cells from reverse current damage.
Question 6: A rooftop PV system inspection reveals that module frames are bonded using module-to-module bonding washers but the first and last modules in each row are not connected to the equipment grounding conductor. What code requirement is violated?
- NEC 690.43 requiring all exposed metal parts to be grounded (Correct answer)
- NEC 690.35 covering ungrounded systems
- NEC 705.12 covering point of connection
- NEC 230.24 covering clearances
Correct answer: NEC 690.43 requiring all exposed metal parts to be grounded
NEC 690.43 requires all exposed non-current-carrying metal parts of PV module frames and equipment to be connected to an equipment grounding conductor.
Question 7: When inspecting combiner box connections, a technician measures a 2V voltage drop across a string fuse under load. The fuse is rated for the correct ampacity. What does this reading indicate?
- Normal operation within tolerance
- A loose or corroded fuse connection creating excessive resistance (Correct answer)
- The string is producing higher than expected current
- The fuse has a lower voltage rating than required
Correct answer: A loose or corroded fuse connection creating excessive resistance
A significant voltage drop across a properly rated fuse indicates high resistance at the fuse or its connection, typically from corrosion or a loose connection that requires remediation.
NABCEP Electrical Component Inspection 2
During a PV system inspection, you notice the output circuit conductors are routed through metal conduit with no separation from the grounding electrode conductor.
What is the primary concern?