NABCEP System Maintenance 5

Question 1

A battery-based system's charge controller is in float mode but the battery voltage is consistently 0.3V below the float setpoint. What is the most likely cause?

Accepted Answer

The battery temperature compensation sensor is reading incorrectly high temperature

Answer

Temperature-compensated charging reduces voltage setpoints as temperature rises; a sensor reading falsely high temperature causes the controller to reduce its float voltage target, making actual measured voltage appear low.

Question 2

What is the purpose of performing a 'string voltage' measurement at the combiner box on each individual string separately (with other strings disconnected)?

Accepted Answer

To identify a shorted string fuse or reverse-polarity connection that would be masked by parallel string measurements

Answer

Testing each string individually in open-circuit while other strings are disconnected reveals shorted fuses (which would show lower-than-expected voltage) and reverse-polarity wiring that would be masked by parallel combination.

Question 3

When replacing a failed string inverter, which of the following must be verified before energizing the new unit?

Accepted Answer

That the DC input voltage and current ratings of the new inverter are compatible with the PV array's Voc, Vmp, and Isc values

Answer

The replacement inverter must be verified compatible with the existing array's electrical characteristics—particularly that array Voc does not exceed the inverter's maximum DC input voltage and that Isc is within the input current rating.

Question 4

A monitoring system shows that a rooftop PV system's daily energy production peaks at a lower value every few weeks in a repeating pattern. What is the most likely explanation?

Accepted Answer

Cyclic soiling and cleaning pattern, or seasonal tree/vegetation shading growing then being trimmed

Answer

A repeating cyclic pattern in production dips most commonly reflects accumulating soiling (pollen, dust, bird droppings) between cleaning events, or seasonal shading from vegetation that follows a growth and trimming cycle.

Question 5

What information must be documented and retained after completing any corrective maintenance on a PV system?

Accepted Answer

A record of the fault found, work performed, components replaced, test results, and technician credentials

Answer

Comprehensive maintenance records documenting the fault, corrective actions, replaced components, post-repair test results, and technician information are required for warranty support, regulatory compliance, and future troubleshooting.

(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 5