NABCEP PV flashcards
NABCEP PV · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Solar window
- The unobstructed period, typically 9 a.m. to 3 p.m. solar time, when shade-free sun is most valuable; design arrays to avoid shading in this window.
- Magnetic declination
- The angle between true north and magnetic north at a location; correct compass readings by this angle when setting array azimuth for design.
- Latitude tilt rule
- For year-round output, set fixed-tilt arrays near site latitude; latitude minus 15 degrees favors summer production, while latitude plus 15 degrees favors winter production.
- Roof load allowance
- Rooftop PV typically adds two to four pounds per square foot for rack-mounted systems; confirm structural capacity and use ballasted or elevated racking when required.
- STC rating
- Standard Test Conditions use 1000 W/m² irradiance, 25°C cell temperature, and AM 1.5 spectrum; module nameplate power is rated at STC.
- Cold-temperature Voc
- Open-circuit voltage increases as cell temperature falls; calculate maximum string voltage at the coldest expected cell temperature to remain below equipment voltage ratings.
- DC/AC ratio
- The ratio of array DC nameplate power to inverter AC output; typical designs fall between 1.0 and 1.3, with clipping accepted when energy gain exceeds losses.
- Voltage drop target
- A design limit for conductor voltage loss, commonly about 2 percent on DC circuits and 3 percent on AC circuits, for a total near 5 percent.
- Clamping zone
- The manufacturer-approved area on a module frame where mounting clamps may be placed; clamping outside these zones can damage the module or void warranty.
- Flashing
- A weatherproofing detail that seals roof penetrations, typically using flashed standoffs and sealant; sealant alone is not a primary waterproofing method.
- Equipment grounding conductor
- The conductor that bonds non-current-carrying metal parts together and to the grounding electrode; size it per NEC Table 250.122 based on the overcurrent device rating.
- Conduit expansion fitting
- A fitting that permits conduit movement during thermal expansion and contraction; it prevents buckling or pulled terminations on long straight runs.
- Insulation resistance test
- A commissioning test that applies high DC voltage between conductors and ground; a reading of at least one megohm generally indicates acceptable insulation.
- I-V curve trace
- A plot of current versus voltage for a module or string; comparing the measured curve with the expected shape reveals shading, mismatch, or bypass-diode failures.
- Anti-islanding test
- A commissioning check confirming that the inverter stops exporting power when the utility grid is disconnected, protecting line workers during outages.
- As-built documentation
- Final drawings, equipment serial numbers, test results, and labeling records delivered at commissioning; they support maintenance, warranty claims, and future inspections.
- Thermal imaging
- Infrared scanning of modules and connections under load; hotspots reveal cell cracks, failed bypass diodes, or loose terminations that reduce production.
- Ground fault
- An unintended current path from a PV conductor to ground; isolate the fault with an insulation tester and do not re-energize until repaired.
- Performance ratio
- Actual energy output divided by theoretical output based on irradiance and nameplate rating; it normalizes production comparisons across weather and site conditions.
- String fuse failure
- A blown fuse often indicates reverse polarity, a short circuit, or excessive reverse current; compare string currents with a clamp meter before replacing it.
- PV live in light
- PV modules produce voltage whenever illuminated, so DC conductors remain energized even when the inverter or AC disconnect is off; treat them as live.
- Fall protection trigger
- OSHA generally requires fall protection when working six feet or more above a lower level; use guardrails, personal fall arrest, or nets.
- Lockout tagout
- An energy-isolation procedure using locks and tags; on PV systems the AC disconnect stops export, but module-side DC remains energized.
- Arc flash PPE
- Personal protective equipment rated for the calculated incident energy; PV DC arcs do not self-extinguish, so use insulated tools and appropriate gear.
- 120 percent rule
- An NEC allowance permitting the main breaker plus the PV breaker to total up to 120 percent of the busbar rating in a center-fed panel.
- Rapid shutdown
- An NEC 690.12 requirement to reduce conductor voltage at the array boundary to a safe level within a specified time for emergency responders.
- PV source circuit ampacity
- PV source conductors must carry 125 percent of short-circuit current per NEC 690.8, with additional adjustment for temperature and conduit fill.
- Interconnection label
- A permanent plaque identifying the PV system, disconnect location, and maximum output; required by code and utility for safe operation.
- Change order
- A written contract amendment describing added or removed work, price, and schedule; obtain customer signature before performing the changed work.
- Investment tax credit
- A federal tax credit equal to a percentage of eligible PV system costs; verify current rates and eligibility because the schedule changes by year.
- Net metering
- A utility billing arrangement that credits exported solar energy against consumption; check the tariff for credit rates, caps, and true-up rules.
- Workmanship warranty
- A contractor guarantee covering installation defects for a stated period, commonly five to ten years; it is separate from manufacturer equipment warranties.