NABCEP System Maintenance 2

Question 1

During a routine inspection, you find that a string of modules has an open-circuit voltage (Voc) reading 15% below the expected value. What is the most likely cause?

Accepted Answer

One module in the string is completely disconnected or has a broken cell string

Answer

A single fully disconnected module or broken cell string reduces string Voc by approximately one module's Voc, which for a typical 20-module string is about 5%, but severe internal failures can drop it further; the most direct cause of a significant Voc drop is an open-circuit internal to one module.

Question 2

What is the recommended torque specification procedure when re-tightening module frame bolts on a racking system during preventive maintenance?

Accepted Answer

Follow the racking manufacturer's specified torque values using a calibrated torque wrench

Answer

Racking manufacturers publish specific torque values for all fasteners, and using a calibrated torque wrench to meet those values ensures structural integrity without over-stressing components.

Question 3

A battery-based off-grid system shows the battery bank voltage sagging excessively under load even though the state of charge reads 80%. What should the technician check first?

Accepted Answer

Internal resistance or cell condition of individual batteries

Answer

Excessive voltage sag under load with a seemingly high SOC indicates high internal resistance, which is a common sign of battery aging, sulfation, or cell failure.

Question 4

When performing thermographic (infrared) inspection of a PV array, what condition is the inspector primarily trying to identify?

Accepted Answer

Hot spots caused by cell damage, soiling, shading, or bypass diode failure

Answer

Thermographic inspection identifies hot spots—localized elevated temperatures in cells or modules—which indicate defects, shading mismatch, soiling, or failed bypass diodes that cause power loss and potential fire risk.

Question 5

An inverter's ground fault protection device (GFPD) has tripped. After clearing the fault and resetting, what must the technician verify before returning the system to service?

Accepted Answer

That the ground fault has been identified and corrected, not just cleared

Answer

Resetting a GFPD without identifying and correcting the root cause of the ground fault creates a fire and safety hazard; the fault must be located and repaired before the system is re-energized.

(NABCEP) North American Board of Certified Energy Practitioners Solar Practice Test

(NABCEP) North American Board of Certified Energy Practitioners Solar Practice Test

NABCEP System Maintenance 2