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

7 cards from real NABCEP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Commissioning flashcards as text

  1. During commissioning of a grid-tied PV system, the installer measures an open-circuit voltage significantly higher than the STC rating. What is the most likely cause?

    Answer: Low ambient temperature increasing Voc

    PV module Voc increases as temperature decreases, so cold ambient conditions can push array voltage well above STC (25°C) nameplate values.

  2. Which instrument is most appropriate for verifying that PV source circuits are not cross-connected at the DC combiner box during commissioning?

    Answer: Low-range DC voltmeter with polarity check

    Measuring DC polarity and voltage at each source circuit input confirms correct wiring before energizing the combiner.

  3. A commissioning checklist item requires torquing all DC lugs. Why is under-torquing particularly dangerous in a PV system?

    Answer: It can cause high-resistance connections leading to arcing and fire

    Loose connections create resistance, which generates heat and can produce DC arcs that are difficult to extinguish.

  4. When commissioning a battery-based off-grid system, what state of charge should the battery bank be at before first connecting PV source circuits?

    Answer: Fully charged to 100% SOC via AC charging

    Manufacturers typically require batteries to be fully charged before initial PV connection to verify charge controller set points and prevent sulfation.

  5. During AC-side commissioning, the installer observes that the utility revenue meter is spinning backward before the interconnection agreement is in place. What should be done immediately?

    Answer: Disconnect the system from the grid immediately

    Exporting power before the utility has approved interconnection violates the interconnection agreement and can create safety and billing issues.

  6. What does the commissioning step of verifying 'anti-islanding' confirm in a grid-tied inverter?

    Answer: The inverter disconnects from the grid during a utility outage

    Anti-islanding ensures the inverter shuts down when the utility grid goes down, protecting utility workers from energized lines.

  7. A string inverter commissioning log shows Vpv = 420 V but the MPPT window is 200–480 V. What does this indicate?

    Answer: String voltage is within the MPPT operating range — normal

    420 V falls within the 200–480 V MPPT window, so the inverter will operate normally and track maximum power.