NABCEP Electrical Component Inspection 4 — Questions and Answers
Question 1: An inspector observes that the PV system's rapid shutdown (RSD) initiator is located inside the building at the main service panel, but there is no RSD label at the roof access point. What NABCEP/NEC concern does this raise?
- The initiator must be located outdoors near the array
- First responders must be able to identify and operate RSD from outside the building (Correct answer)
- The RSD system must be wireless to comply with NEC 690.12
- The initiator must be at the utility meter location
Correct answer: First responders must be able to identify and operate RSD from outside the building
NEC 690.12 and fire codes require RSD controls to be labeled and accessible at locations where first responders will need to de-energize the rooftop array.
Question 2: During an inspection, you find that the equipment grounding conductors for the PV array are sized at 10 AWG copper. The PV source circuit overcurrent protection is 20A. Is this sizing correct per NEC 690.45?
- No, EGCs must always be sized at 6 AWG for PV systems
- Yes, 10 AWG copper is the minimum allowed for a 20A OCPD per NEC Table 250.122 (Correct answer)
- No, EGCs must be sized to 125% of Isc regardless of OCPD size
- Yes, any AWG is acceptable if the conduit provides grounding continuity
Correct answer: Yes, 10 AWG copper is the minimum allowed for a 20A OCPD per NEC Table 250.122
Per NEC 250.122 (referenced by 690.45), a 20A OCPD requires a minimum 12 AWG copper EGC, so 10 AWG copper exceeds the minimum and is acceptable.
Question 3: During a PV system inspection, you find that module-level power electronics (MLPE) are installed but the system does not have rapid shutdown capability. The building permit was issued in 2018. What applies?
- RSD is not required for systems with MLPE installed
- The applicable code at time of permit is the governing requirement (Correct answer)
- All PV systems must be retrofitted to current NEC RSD requirements
- RSD is only required for systems over 10 kW
Correct answer: The applicable code at time of permit is the governing requirement
The applicable edition of the NEC adopted at the time the permit was issued governs the installation; retrofitting to a newer code edition is generally not required unless required by the AHJ.
Question 4: An inspection of a string inverter reveals that the DC input terminals are labeled 'PV1+' and 'PV1-' but only one string is connected to the inverter. The second input pair is left open. What is the concern?
- An unconnected input will cause the inverter to fault immediately
- Open DC input terminals may arc if accidentally contacted and present a shock hazard (Correct answer)
- The inverter efficiency will be reduced by 50% with one input unused
- Open inputs will cause ground faults in the connected string
Correct answer: Open DC input terminals may arc if accidentally contacted and present a shock hazard
Unused DC input terminals on inverters should be covered with appropriate caps to prevent accidental contact with energized conductors or foreign object intrusion.
Question 5: A technician performing a visual inspection of a rooftop PV array notices several modules have yellowish-brown discoloration spreading from the busbars across the cell surfaces. What condition does this indicate?
- Normal UV tanning of the EVA encapsulant with age
- EVA delamination and potential hot spot formation requiring replacement evaluation (Correct answer)
- Thermal expansion marks from repeated heating and cooling cycles
- Soiling patterns from organic debris accumulation
Correct answer: EVA delamination and potential hot spot formation requiring replacement evaluation
Yellowish-brown discoloration (browning) spreading from busbars indicates EVA encapsulant degradation and delamination, which increases series resistance and can lead to hot spots and power loss.
Question 6: When inspecting a battery energy storage system (BESS) connected to a PV system, you find the battery room ventilation fan is wired to a standard 15A GFCI outlet. What is the code concern?
- GFCI protection is not required in battery rooms
- Ventilation equipment must be on a dedicated circuit with continuous-duty rating (Correct answer)
- Battery rooms require 20A circuits for all equipment
- GFCI protection is incompatible with variable-speed fan motors
Correct answer: Ventilation equipment must be on a dedicated circuit with continuous-duty rating
Battery ventilation is a life-safety function and must be on a dedicated, reliable circuit; GFCI protection can nuisance-trip and interrupt critical ventilation during hydrogen gas evolution.
Question 7: During inspection of a DC combiner box, an inspector finds that the positive and negative source circuit conductors from different strings are bundled together with a cable tie. What is the issue with this practice?
- Bundling reduces system efficiency due to proximity losses
- Bundled conductors require ampacity derating per NEC 310.15(C) (Correct answer)
- Positive and negative conductors must always be in separate conduits
- Bundling is only permitted outside of listed enclosures
Correct answer: Bundled conductors require ampacity derating per NEC 310.15(C)
When multiple current-carrying conductors are bundled together, NEC 310.15(C) requires ampacity correction factors to be applied to account for mutual heating effects.
NABCEP Electrical Component Inspection 4
An inspector observes that the PV system's rapid shutdown (RSD) initiator is located inside the building at the main service panel, but there is no RSD label at the roof access point.
What NABCEP/NEC concern does this raise?