NABCEP System Maintenance & Troubleshooting 2

Question 1

A string of PV modules shows significantly lower output than adjacent strings on the same array. The first diagnostic step should be to:

Accepted Answer

Measure open-circuit voltage (Voc) of each module in the string

Answer

Measuring Voc on each module individually isolates whether the issue is a single failed module, partial shading, or wiring fault.

Question 2

During routine maintenance, a technician finds that an inverter's ground fault protection device (GFPD) has tripped. The safest next step is to:

Accepted Answer

Disconnect the array and inverter, then inspect wiring for ground faults before resetting

Answer

A tripped GFPD indicates a real or suspected ground fault; the system must be de-energized and inspected before resetting to prevent fire or shock hazard.

Question 3

Which condition is MOST likely indicated when infrared thermography reveals a hot spot on a single cell within a PV module?

Accepted Answer

Cell crack, delamination, or bypass diode failure

Answer

Localized hot spots on individual cells typically indicate physical damage such as cracks, delamination, or a failed bypass diode forcing current through a resistive cell.

Question 4

A battery-based off-grid system shows that batteries are consistently undercharged after several sunny days. The MOST likely cause is:

Accepted Answer

Charge controller set-point voltage too low for battery chemistry

Answer

If the charge controller's absorption or float voltage set point is lower than the battery manufacturer's specification, the batteries will never reach full state of charge.

Question 5

When performing IV curve tracing on a PV string, a 'stepped' curve with multiple knee points most likely indicates:

Accepted Answer

Partial shading or module mismatch within the string

Answer

Multiple inflection points on an IV curve are characteristic of partial shading or module mismatch, where bypass diodes in some modules are conducting.

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

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

NABCEP System Maintenance & Troubleshooting 2