NABCEP Commissioning 4

Question 1

What is the correct sequence for de-energizing a grid-tied PV system during a commissioning fault investigation?

Accepted Answer

Open AC disconnect first, then DC disconnects from array

Answer

The inverter AC disconnect is opened first to stop current flow, then DC disconnects are opened to safely de-energize the array side.

Question 2

A newly commissioned microinverter system shows that one microinverter is offline in the monitoring portal. Which commissioning step would identify this before system handover?

Accepted Answer

Comparison of expected vs. actual microinverter count in the monitoring system

Answer

Commissioning should include verifying that every installed microinverter is communicating and visible in the monitoring platform before owner handover.

Question 3

During commissioning, a string of 10 modules measures 385 V Voc instead of the expected 410 V. Which condition would most likely explain this discrepancy without indicating a fault?

Accepted Answer

Ambient temperature is 35°C instead of the STC 25°C

Answer

Higher ambient temperatures reduce Voc; at 35°C the array voltage will be lower than the STC (25°C) nameplate calculation.

Question 4

Which document must the installer obtain from the utility before energizing the point of common coupling (PCC) on a grid-tied system?

Accepted Answer

Utility permission to operate (PTO) or interconnection approval

Answer

Utility permission to operate (PTO) is required before the system can export power to the grid; energizing without it violates the interconnection agreement.

Question 5

What is the primary purpose of measuring the short-circuit current (Isc) of each source circuit at the combiner during commissioning?

Accepted Answer

To verify each string is producing and confirm no open-circuit failures

Answer

Measuring Isc at the combiner confirms each string is producing current and helps identify strings with failed modules, bad connections, or incorrect wiring.

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

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

NABCEP Commissioning 4