NABCEP SH Associate cheat sheet

Daily energy demand (Wh/day) = sum of (appliance wattage × hours used per day) for every load; add an inverter/system loss factor of roughly 1.3–1.5 to size array output.

Solar window is the period with no shading; usable peak sun hours (PSH) is the daily insolation in kWh/m²/day, numerically equal to equivalent hours at 1 kW/m².

Shading survey tools: solar pathfinder or smartphone sun-path app plus a physical walk of the array footprint at multiple times of day; record obstructions with azimuth and elevation.

Roof structural check: confirm rafter/truss spacing, span, and condition; verify dead load capacity for modules, racking, and ballast before layout.

Roof surface assessment: measure usable area, note penetrations, parapets, HVAC units, skylights, and set required fire-access pathways per local code.

Load analysis distinguishes continuous loads (×1.25 for conductor/OCPD sizing), intermittent loads, and surge loads such as motor starting.

Battery-based systems: usable capacity (Wh) = nominal capacity (Wh) × depth of discharge × inverter/round-trip efficiency; size autonomy in days of no-sun.

Site data to record: latitude/longitude, tilt and azimuth of mounting plane, annual and worst-month PSH, ambient temperature range, snow/wind loads, and utility interconnection point.

NEC Article 690 governs PV systems; Article 690.12 requires rapid shutdown - conductors within 1 ft of the array and 3 ft of conduit must be de-energized to ≤30 V within 30 seconds of shutdown.

NEC 690.7: maximum PV system voltage = module Voc × correction factor for lowest expected ambient temperature, and it must not exceed inverter/equipment ratings.

NEC 690.8: continuous current = Isc × 1.25 for conductor ampacity; OCPD rating = Isc × 1.25 × 1.25 (1.56), then rounded to the next standard size.

Arc-flash and shock hazards persist because modules are energized whenever illuminated; cover modules or work at night/low light for DC conductor work.

Required PPE: voltage-rated gloves, arc-rated clothing per incident-energy analysis, safety glasses, and insulated tools; lockout/tagout the AC side before service.

Fall protection is required at heights per OSHA 1926 Subpart M (generally 6 ft in construction); use harness, anchor points, and guardrails.

Standards to know: UL 1703/UL 61730 (modules), UL 1741 (inverters/grid support), UL 2703 (racking/bonding), UL 9540 (energy storage), IEC 61215/61730.

Certifications: NABCEP PV Associate, PV Installation Professional, and Solar Heating; state electrical licensing and local AHJ permitting are separate requirements.

Hot climates: high cell temperature reduces voltage and power (typical power temp coefficient about −0.3 to −0.45 %/°C); specify modules with better temperature coefficients and ensure array ventilation.

Cold climates: Voc rises at low temperature, so use the coldest expected ambient for maximum voltage calculations; snow shedding favors steeper tilt (≥40°) and smooth frameless modules.

Coastal/marine: specify corrosion-resistant racking (anodized aluminum, stainless hardware), avoid dissimilar-metal contact, and account for salt-fog testing.

Dusty/arid: soiling losses can reach 5–20 %; plan cleaning schedules, use anti-soiling coatings, and consider higher tilt for self-cleaning.

Off-grid applications: size array for worst-month PSH, include battery autonomy (typically 2–5 days), and use MPPT charge controllers for efficiency.

Grid-tied with battery backup: hybrid inverters with critical-load subpanels; verify backup transfer time and surge capacity for motor loads.

Solar thermal vs PV: SHW (solar hot water) uses collectors and a heat-transfer loop; PV uses modules and inverters; hybrid PV-T combines both but adds complexity.

Utility-scale vs rooftop: ground-mount uses single-axis trackers in high-DNI regions; rooftop prioritizes usable area and structural limits over tracker gains.

Fixed-tilt in the northern hemisphere faces true south (azimuth 180°); tilt approximately equal to latitude maximizes annual yield, with steeper tilt favoring winter and shallower favoring summer.

Azimuth deviations of ±15–20° from true south typically cost only a few percent of annual yield; larger deviations are weighed against roof constraints.

Row spacing: avoid inter-row shading between about 9 a.m. and 3 p.m. on winter solstice; spacing depends on tilt, latitude, and module height.

Racking types: flush-mount (roof-parallel), tilted/standoff, ballasted (no penetrations, for flat roofs), and ground-mount (pole or fixed).

Roof-mount attachment: lag bolts into structural members, flashed penetrations, and standoff heights that allow airflow and module cooling.

Module clamping: follow manufacturer clamp zones and torque specs; do not clamp on non-clampable frame edges; allow expansion gaps.

Grounding/bonding: bond module frames and racking with listed bonding hardware (UL 2703) and a continuous equipment grounding conductor.

Commissioning: verify string polarity, Voc and Isc per string, insulation resistance, and inverter startup; document with as-built and photos.

Balance of system (BOS) includes racking, wiring, disconnects, OCPD, combiners, grounding, inverters, charge controllers, and monitoring.

Conductor sizing: ampacity ≥ 1.25 × Isc for PV source/output circuits; account for temperature correction and conduit fill derating.

String combiners: fuse each string at 1.56 × Isc (per NEC) and use a DC-rated disconnect; verify fuse voltage rating exceeds max system voltage.

Inverters: string inverters for simple arrays, microinverters for module-level MPPT and shade tolerance, and hybrid for battery integration; match DC/AC ratios (typically 1.0–1.3).

Charge controllers: PWM for small systems with matched voltages; MPPT for larger systems and higher array voltages; size to array Isc and battery voltage.

Disconnects: DC-rated for PV circuits; AC disconnect accessible to utility/first responders; rapid shutdown devices for roof-mounted arrays.

Wiring methods: use PV-rated (sunlight-resistant, wet-rated) conductors outdoors, UV-rated conduit, and proper strain relief; keep DC and AC circuits separated.

Materials: use corrosion-resistant hardware, listed connectors (MC4-compatible), and proper junction boxes; avoid mixing connector brands.

Cleaning: remove soiling (dust, pollen, bird droppings) with water and soft brushes; avoid abrasive tools; schedule based on soiling rate and rainfall.

Visual inspection: check for cracked glass, hot spots, delamination, discoloration, snail trails, and loose or corroded connections.

Electrical checks: measure string Voc and Isc, compare to commissioning baseline; check for ground faults, insulation resistance, and inverter fault logs.

Thermal imaging identifies hot spots, bypass-diode failures, and loose terminations not visible to the eye.

Racking/hardware: torque-check bolts, inspect for corrosion and loose clamps, verify flashing and roof seal integrity after storms.

Battery maintenance (if present): check electrolyte (flooded), terminal torque, ventilation, temperature, and state of charge; replace at end of life.

Inverter maintenance: clean/replace air filters, verify cooling, check firmware and monitoring connectivity, and record fault codes.

Documentation: maintain a maintenance log with dates, findings, and corrective actions; track performance ratio to detect degradation trends.