Design (18.3%)

PVA · 55 questions

• A homeowner in a zoned city wants a 7-kW rooftop system that will export power. The city requires a building and electrical permit, the utility requires an interconnection application, and power cannot flow until final sign-off. Which AHJ permitting, utility, and inspection sequence meets requirements?
• You are sizing a home with 9.6 kW DC of modules paired to a 7.6 kW AC inverter for a south roof with no shade and a tight budget. The inverter max DC input and voltage window both pass. Which compatibility check confirms the DC:AC ratio supports expected clipping and output?
• A technician commissions a ground-mount array on a hot July afternoon and records each string's voltage at the open terminals before the DC disconnect closes. Every string reads several volts below the module datasheet's listed open-circuit voltage, while connections and string counts verify as built. Which factor explains the lower open-circuit voltage readings?
• You are sizing a 9.6-kW DC rooftop array of south-facing modules paired with an 7.6-kW string inverter for a home with steady midday loads. The module specs fit the inverter MPPT voltage window and the max input current is not exceeded. Which inverter compatibility check confirms an acceptable DC:AC ratio for this design?
• A designer reviews two 400 W datasheets at standard test conditions for a 150 V charge controller limit in cold weather. Both show similar power but different open-circuit voltage and short-circuit current values on the label. Which reading of module specs guides the string sizing choice?
• A 9 kW home retrofit in a historic district needs a building permit, utility interconnection approval, and final sign-off before permission to operate. In this jurisdiction the utility reviews an interconnection application only after the AHJ approves the plans, its approval is required before construction, and the AHJ's final inspection must pass before anyone energizes. The designer must explain the sequence and who enforces each step. Which explanation best describes permitting, utility, and AHJ inspection requirements?
• An installer on a duplex roof finds two rail splice kits, unclear torque marks, and a wrinkled quick-start sheet that conflicts with memory. The inspector arrives in one hour with strict labeling checks. Which use of datasheets and manuals resolves the conflict correctly?
• A designer compares two 10-kW bids in a hot, dusty valley with rare rain, nearby almond harvest dust, and 105°F summer peaks. Both use the same modules and tilt. Which design adjustment best accounts for weather and soiling effects on performance?
• A 50 kW ground array in a dusty farm area faces hot summers, winter snow, and seasonal pollen that coats modules and raises cell heat. The designer must adjust expected yield for climate losses. Which design allowance best accounts for weather and soiling effects?
• You get a permit set for a 9-kW home showing a north arrow, property lines, a 3-ft ridge setback, vent locations, and two subarrays with string labels. The foreman asks for rail spans and wire routing confirmation. Which plan-reading task extracts site plans and array layouts for the install?
• A designer is adapting a rail kit the manufacturer ships for landscape rows to a barn roof where the modules will hang in portrait. The racking manual lists permitted orientations, clamp zones and rated loads, while the module datasheet adds frame depth and weight. Which three racking-manual checks must the designer confirm before releasing the layout to the crew?
• A ground-mount crew is staking row spacing for a 60-module array. Sheet A-1, the site plan, dimensions the rows at 12 feet from a scaled dimension string, and its title block notes that enlarged layouts and details govern and that scaling from that sheet is prohibited. Sheet A-4 is labeled 'Enlarged array layout' and dimensions the rows at 14 feet with rows running east to west, while detail M-1 shows 15-foot spacing for rows running north to south. This job's rows run east to west. Which source should the crew stake for this job's row spacing?
• A small metal fabrication shop has approved a 30 kW rooftop array on its 480Y/277 V, three-phase, 60 Hz service, and the designer has reserved a 100 A breaker space for the inverter in the main switchboard. A low-cost unit in stock lists 208 V three-phase output, 80 A continuous output, 60 Hz, and 150% surge for 10 seconds. Which inverter specification check determines whether this unit may be connected directly to the shop service?
• You are staging material for a 18-kW commercial rooftop using the permit plan set. The one-line shows the service, inverter, and AC disconnect, while a separate string diagram details modules per string, homeruns, and combiner inputs. The foreman asks what to pull from the string diagram for wire pulls. Which use of plan-set diagrams guides your wire pull correctly?
• You review permit plans for a 40-kW commercial rooftop with three inverters and 12 strings where crews confuse conduit runs, phase balance, and string polarity. The set has one-line, three-line, and string wiring sheets. Which diagram interpretation best assigns each sheet to its troubleshooting use?
• A designer must compare two small commercial sites: a sunny desert roof with 5.8 peak sun hours and a cloudy coastal roof with 3.2 peak sun hours using the same 10-kW array. Which application of peak sun hours should the designer use to predict the difference in daily performance?
• A designer must pair a single-phase residential string inverter with a 120/240V home service where the utility holds 60 Hz and the owner runs a well pump that draws a brief high inrush on startup. Which inverter specification check best confirms voltage, current, frequency, and surge compatibility?
• A designer in Albuquerque compares two fixed 8-kW proposals for a school: Site A averages 6.2 peak sun hours with light soiling, and Site B averages 4.8 peak sun hours with clear access. Both use the same gear and tilt. Which use of peak sun hours best predicts relative energy for design and performance?
• You are pulling DC homeruns in rooftop conduit for a 10-kW home where the attic reaches high heat, the conduit sits in full sun on the roof, and one raceway transitions through a damp crawlspace. The plan calls for 90C-rated insulation with wet-location and sunlight resistance. Which conductor choice meets temperature, ampacity, UV, and moisture needs?
• A designer is assessing the existing service equipment at a small bakery converted from a 1965 farmhouse before a 10.4 kW array is permitted. The meter-main is a listed 150 A, 120/240 V unit with a legible nameplate and an undamaged exterior. Inside the load center fed from it, the wire insulation at two breaker lugs is melted and the bus behind them is heat-discolored, while four breaker spaces remain free. Which service equipment finding must be corrected before the PV interconnection equipment is added?
• A designer in Portland must place 24 modules on a split roof where a chimney shades the lower west section from 2 to 5 p.m. and a maple shades the east edge in the morning. Production modeling is required for the permit. Which shading analysis best informs layout and energy estimates for design and performance?
• You are checking a residential plan set for exposed rooftop source circuits in conduit on a hot dark roof that stays wet and sunlit. Notes call for continuous current, high ambient derate, and wet location use. Which conductor selection meets temperature rating, ampacity, UV and moisture requirements?
• A site survey of a 1990s house shows a 200 A service panel with a 225 A bus rating, ten free breaker spaces, and a rust-free enclosure. The homeowner wants a 9.6 kW array whose inverter output breaker is 40 A. Which evaluation determines whether this load-side connection fits the panel's busbar capacity?
• A designer is laying out a 8-kW home array where a tall chimney shades the lower west roof from 3-5 pm and a neighbor tree shades the east roof until 9 am. Year-round production matters most to the owner. Which shading analysis result should guide final module placement?
• At a pre-install huddle for a 150-kW ground-mount site, the crew lead points to a circle on the array plan marked '3 / S-501' with an arrow at a pier. The drawing index splits sheets into E-series and S-series, and the general notes require embeds to be verified before concrete. Which sheet should the crew lead open to see the pier's anchor bolts and rebar?
• A designer is laying out a 7-kW fixed roof array for a suburban home at 40 degrees north latitude with a low-slope hip roof, light tree shade to the east, and a customer wanting best yearly energy. Which array tilt and azimuth choice should the designer recommend for annual performance?
• A homeowner wants overnight backup for a fridge, lights, WiFi, and a small well pump during 4-hour outages, plus daily time-of-use shifting. Two batteries are quoted with different kWh, kW, and inverter pairings. Which evaluation best matches storage system specs to the need?
• A junior installer is fitting rails on a 96-module ground-mount array. At every post-to-rail joint the layout sheet shows a circle split by a horizontal line, with 4 above it and S2 below. The set also holds a site plan, an equipment schedule and an electrical single-line, and she needs to see how the rail seats in the post cap and how the splice is made. Which sheet does that callout point her to?
• A designer must place a 6-kW fixed array on a low-slope commercial roof in the northern hemisphere with room to face south, southeast or southwest and tilt 5, 20 or 35 degrees while avoiding row shading. Which tilt and azimuth choice maximizes annual energy?
• A homeowner wants a 10-kWh-class wall battery for evening lights, fridge, and internet through short outages, AC-coupled to an existing 6-kW inverter on a 200-A panel. Which evaluation should the associate perform to compare storage system specs?
• A new designer assembled a 11-kW residential rooftop packet with datasheets, a single-line diagram, site plan, and structural letter, and the town reviewer returned it asking for the missing submittal forms and proof of utility review on a standard home with no variance needed. Which identification of permit documents best completes the application?
• A proposal for a 15-kW rooftop system promises 22 MWh per year, yet the site has high summer heat, long wire runs, dusty air, and a shaded parapet, and the client asks why modeled output is lower. Which derating and system-loss explanation should the designer give to justify the adjusted yield?
• A designer must choose modules, inverters, and racking for a permitted home system that the inspector and utility will approve. Suppliers offer mixed listed and unlisted deals. Which recognition of NRTL listing and product safety standards best guides selection?
• A designer prepares a permit package for an 8-kW home rooftop system with a supply-side tap. The city plan check asks for layout, wiring, and safety labels in one submittal. Which permit document package should the designer submit to show code-compliant electrical layout?
• A designer models an 8-kW rooftop array rated at STC for a dusty site with long DC runs and a hot attic. Notes list soiling loss, wiring voltage drop, elevated cell temperature, and published inverter efficiency. Which sizing adjustment correctly applies derating factors and system losses to predict output?
• A designer is reviewing cut sheets for a 9-kW home bid using listed modules, a listed string inverter, and listed racking on a city permit that requires third-party safety proof. One vendor offers cheaper gear marked CE only with no NRTL mark. Which equipment specification choice confirms NRTL listing and product safety standards?
• A drafter is building the load summary for a solar canopy at a transit center, where steel posts sit on concrete piers, tool totes are staged on the beams during the install, and backfill is compacted around each pier. Buses roll across a joint in the pavement beside the posts all day. Which line item should the drafter flag as the dynamic load on this structure?
• A homeowner is quoted a 7-kW DC array in a location averaging 5 peak sun hours daily, with an expected performance ratio of 0.78 after all losses and a south-facing shade-free roof. Which calculation correctly estimates energy production and efficiency for this proposed system?
• A design team is permitting a 15-kW residential array on a mountain home at 7,500 ft with 60-psf ground snow, 120-mph wind exposure, and a known seismic zone on composite shingles. The AHJ wants stamped racking proof. Which location-load review should the designer require to approve the racking and attachment plan?
• You size racking for a lakefront home with open wind fetch, heavy lake-effect snow, and a mapped quake zone, using flush-mount rails on comp shingles. The building office flags structural review. Which location-load review for wind, snow, and seismic forces should the designer document for the racking choice?
• A designer must confirm whether a proposed 15 kW DC array paired with a 12 kW inverter meets a client's 20,000 kWh annual goal. Site data for the location gives 1,700 kWh of yearly energy per installed kilowatt, and the loss budget for temperature, wiring, soiling, and conversion totals 25%. Which annual production estimate best supports the go or no-go decision?
• An engineer reviews a coastal ground-mount where heavy panels sit still but winter gusts shake racks and crews walk rows for cleaning. Which load distinction should the associate state to separate structural considerations for static from dynamic loads?
• A school wants a 40 kW array but the main roof is shaded, old, and weight-limited while the parking lot needs shade and the field has open sun with trenching room. The board wants low roof risk, driver comfort, and easy mowing access. Which mount comparison among ground, roof, and canopy options best fits these site goals and constraints?
• A 1,600 sq ft home uses about 9,000 kWh per year with steady daytime loads, good south roof space for 9 kW, and the utility limits residential net-metered systems to 7.6 kW AC output with a 40A backfeed breaker. The designer estimates a 7 kW DC array makes about 10,000 kWh yearly with a 7.6 kW inverter. Which array size best balances load coverage with interconnection limits?
• A 12-kW home addition needs plan approval in a jurisdiction that adopts the NEC with state amendments, plus local zoning setbacks and fire access pathways. The designer cites national listing, state electrical rules, and city roof access rules. Which code responsibility assignment should the designer use to show electrical, building and fire code roles?
• A community center wants 40 kW and shade for its lot. Its flat roof is at its load limit and needs new membrane in five years, and its side field is protected wetland that cannot be graded or trenched. The lot gets full sun and the owner will pay more steel cost for dual use. Which mount choice best fits these structural and site limits?
• You survey a 1970s ranch for a 6-kW flush-mount retrofit. The attic shows 2x8 site-cut rafters on 24-inch centers with collar ties, and the roof has three-tab asphalt shingles over one layer with exposed nail heads. Which roofing and framing identification should the designer record to guide the mounting plan?
• You design a 12-kW home system where the city permit desk cites NEC for wiring, IBC for roof loading, and IFC with local setback amendments for fire access. The state adopts NEC with amendments and the AHJ has final say. Which allocation correctly distinguishes electrical, building, and fire code roles?
• A small shop uses about 900 kWh per month with steady daytime fridges, and the roof fits 12 kW DC but the utility letter caps this site at 8 kW AC output. The owner wants the largest allowed bill cut without a service upgrade. Which PV system sizing choice best aligns array output against load analysis and interconnection limits?
• A designer is stringing a 16-module warehouse rooftop array in a hot climate. Each module has a 9.6 A maximum-power current, reaches 43.0 V open-circuit at the coldest design temperature, and falls to 31.0 V at maximum power on a hot roof. The inverter has four MPPT inputs, each with a 15 A maximum operating-current limit and a 600 V maximum voltage, and tracks down to a 160 V floor; all sixteen modules must be installed. Which string layout keeps every module inside the inverter's voltage and current windows at both temperature extremes?
• A designer surveys a 1970s ranch with dimensional shingles over widely spaced sawn rafters and a small addition with engineered trusses plus a flat garage with black membrane. She must choose attachments and spans without overloading frames. Which roofing and framing assessment best guides the plan?
• A designer has twelve 410W modules with 45V open-circuit each, a 30F record low, and a string inverter rated 600V max with a 200-500V MPPT window and 15A input limit. Module voltage rises in cold and the 10A short-circuit current fits well. Which string plan stays within inverter limits across seasons?
• A designer reviews two datasheets for a string calculation on a cold-climate home: Module A lists 41 V open-circuit voltage and 11 A short-circuit current at STC, plus temperature coefficients. Which reading correctly uses STC, open-circuit voltage, and short-circuit current for this design?
• A new hire is confused when the foreman cites OSHA for fall protection, ANSI for harness testing, and NFPA 70E for arc-flash practice on the same commercial rooftop job. The manager wants clear roles. Which workplace safety standard distinction should the trainer use to identify OSHA, ANSI, and NFPA responsibilities?
• You lay out a 100-kW flat-roof design requiring fall protection, safe ladder use, and arc-flash labeling with crew training records. The owner asks which workplace safety standards govern each duty versus electrical installation rules. Which reference correctly identifies OSHA, ANSI, and NFPA workplace safety roles?