NABCEP NABCEP PV Commissioning and Maintenance Specialist 2 — Questions and Answers
Question 1: What maintenance task should be performed on PV module surfaces in dusty or arid climates more frequently than in other regions?
- Recabling
- Cleaning to remove soiling (Correct answer)
- Replacing bypass diodes
- Updating monitoring firmware
Correct answer: Cleaning to remove soiling
Dust and particulate buildup (soiling) reduces light transmission to PV cells and can significantly reduce energy output, requiring more frequent cleaning in arid climates.
Question 2: During annual PV system maintenance, which component's connections should be inspected for corrosion and re-torqued to specification?
- Module glass surfaces
- All DC and AC electrical connections (Correct answer)
- Inverter LCD display
- Monitoring web portal credentials
Correct answer: All DC and AC electrical connections
Electrical connections can loosen or corrode over time, increasing resistance and creating hot spots or arc-fault risks, so they must be inspected and torqued annually.
Question 3: What is the recommended method for detecting hot spots in PV modules during a maintenance inspection?
- Visual inspection only
- Infrared (IR) thermography (Correct answer)
- Clamp meter readings
- Acoustic testing
Correct answer: Infrared (IR) thermography
Infrared thermography reveals thermal anomalies caused by cell cracks, bypass diode failures, or soiling that are invisible to the naked eye.
Question 4: A combiner box fuse blows repeatedly in the same string position. What is the most appropriate next step?
- Replace with a higher-rated fuse
- Inspect the string for a ground fault or short circuit (Correct answer)
- Bypass the fuse position
- Increase the inverter's MPPT voltage range
Correct answer: Inspect the string for a ground fault or short circuit
A repeatedly blown fuse indicates an underlying fault such as a ground fault or short circuit in that string, which must be identified and corrected before replacing the fuse.
Question 5: Which performance metric is most useful for comparing a PV system's actual output to its expected output over time?
- Peak watt rating
- Performance ratio (PR) (Correct answer)
- Open-circuit voltage
- Nominal operating cell temperature (NOCT)
Correct answer: Performance ratio (PR)
Performance ratio compares actual energy yield to the theoretically expected yield, accounting for weather, and is the standard KPI for long-term system health monitoring.
Question 6: What is the primary hazard when performing maintenance on a PV array that cannot be fully de-energized by shutting off the inverter?
- Low voltage shock risk from AC circuits
- PV modules continue to produce DC voltage in daylight even with the inverter off (Correct answer)
- Module glass cracking from thermal stress
- Loss of monitoring data
Correct answer: PV modules continue to produce DC voltage in daylight even with the inverter off
PV modules generate DC voltage whenever light hits them, so DC conductors remain energized even when the inverter and AC breakers are off, posing a shock hazard.
NABCEP NABCEP PV Commissioning and Maintenance Specialist 2
What maintenance task should be performed on PV module surfaces in dusty or arid climates more frequently than in other regions?