NABCEP PV Associate flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Standard Test Conditions

Reference conditions for module ratings: 1000 W/m² irradiance, 25 °C cell temperature, and AM 1.5 spectrum. Nameplate power, voltage, and current are reported at STC.

Insolation vs irradiance

Irradiance is instantaneous power per area (W/m²); insolation is energy accumulated over time, typically kWh/m²/day. Insolation drives daily energy yield estimates.

Temperature coefficient of power

The percent change in module power per degree Celsius above 25 °C. For crystalline silicon it is usually about −0.3% to −0.45% per °C.

Series and parallel wiring

Series connections add voltages and share the lowest current; parallel connections add currents and share the lowest voltage. String design uses both to match inverter windows.

Bypass diode function

A diode across a module substring that provides an alternate current path when cells are shaded or faulty, limiting hot-spot heating and preserving string output.

DC/AC ratio

The ratio of array DC nameplate power to inverter AC rating. Values around 1.1–1.3 are common; higher ratios clip peak output but improve low-light production.

Shading analysis

Evaluation of obstructions across the year using a solar pathfinder or software. Partial shade on one cell can limit an entire series string, so layout matters.

Voltage drop target

Design limit for conductor losses, typically 2–3% on DC and AC circuits. Long home runs or undersized conductors increase drop and reduce delivered power.

Commissioning checks

Verification before energizing: open-circuit voltage, short-circuit current, insulation resistance, polarity, torque, and inverter startup. Results are compared against design values.

Racking wind and snow load

Mounting systems must be listed and rated for site design loads. Roof attachments require flashing and structural review to avoid leaks and failures.

NEC Article 690

The National Electrical Code article covering solar photovoltaic systems, including conductor sizing, disconnects, grounding, arc-fault protection, and labeling requirements.

125% continuous current rule

NEC 690.8 requires PV source and output currents to be multiplied by 125% for conductor and overcurrent sizing, treating array output as a continuous load.

Rapid shutdown

NEC 690.12 requires conductors within the array boundary to be limited to 80 V within 30 seconds of shutdown, protecting firefighters and responders.

Maximum PV system voltage

Calculated using module open-circuit voltage corrected to the lowest expected ambient temperature, using the Voc temperature coefficient from the datasheet.

Equipment grounding conductor

A conductor bonding module frames, racking, and enclosures to the grounding system, providing a low-impedance fault path and shock protection.

DC arc-fault protection

NEC 690.11 requires listed DC arc-fault circuit interruption on PV systems above a threshold voltage to detect and interrupt series arcing.

UL 1741 listing

The safety standard for inverters and interconnection equipment. Listed inverters include anti-islanding functions required for grid-tied operation.

Anti-islanding

A function that stops inverter output when the utility source is lost, preventing an energized island that could endanger line workers during outages.

120% busbar rule

NEC 705.12 permits the sum of overcurrent devices feeding a busbar to reach 120% of its rating when the load breaker is at the opposite end.

Permission to operate

Utility authorization granted after interconnection review and inspection, allowing the grid-tied system to export power legally.

Net metering

A billing arrangement crediting exported energy against consumption. Rules vary by utility and state, so the local tariff must be verified.

Inverter MPPT window

The input voltage range over which the inverter tracks maximum power. String voltage at temperature extremes must stay inside this window.

Fall protection threshold

OSHA 29 CFR 1926 Subpart M requires fall protection at 6 feet or more above a lower level for construction work.

Ladder extension rule

Extension ladders must extend 3 feet above the landing and use a 4:1 slope. Maintain three-point contact and secure the ladder.

Lockout/tagout

OSHA 1926 Subpart K procedure isolating energy sources before work. PV DC conductors remain energized even after AC shutdown, so verify with a meter.

Hazard communication

OSHA 1926.59 requires safety data sheets and training for hazardous chemicals used on site, such as sealants and cleaning agents.

OSHA injury reporting

Employers must report fatalities within 8 hours and severe injuries such as amputations or hospitalizations within 24 hours.

Soiling losses

Reduction in output from dust, pollen, bird droppings, and snow. Typical losses are 1–5% but can exceed 20% in dusty or agricultural areas.

Cleaning best practice

Use deionized or low-mineral water and soft brushes, avoid abrasives and high pressure, and clean when modules are cool to prevent thermal shock.

Hot spot detection

Thermal imaging reveals cells or connections running hotter than neighbors, indicating shading, damage, or failing bypass diodes that reduce output and safety.

I-V curve tracing

Measurement of current versus voltage for a string or module. Deviation from the expected curve identifies underperforming modules, soiling, or mismatch.

Connector and torque checks

Periodic inspection of MC4 mating, mounting hardware torque, and grounding bonds per manufacturer intervals prevents loose connections, arcing, and ground faults.