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Solar PV Quiz



Multiple Choice
Identify the choice that best completes the statement or answers the question.
 

 1. 
A fall protection system must be in place for all work done at heights in excess of
a.
 4 feet
b.
 6 feet
c.
 8 feet
d.
 10 feet
 

 2. 
OSHA rules for personal protection and life-saving equipment are found in OSHA Part 1926:
.
a.
 Subpart A
b.
 Subpart E
c.
 Subpart M
d.
 Subpart Q
 

 3. 
If no specific fall protection system is in place, according to OSHA, it is acceptable to provide fall protection by using a person competent in recognition of fall hazards who
a.
 monitors the operation on closed circuit TV and is in contact with the crew by walkie-talkie
b.
 is a part of the work crew who is capable of warning other workers
c.
 is not a part of the work crew, but who is stationed at the level of the work crew within sight of and speaking distance of the crew, who is capable of warning other workers
d.
 provides safety instructions to the crew before the crew begins work
 

 4. 
Temporarily shorting the output terminals of a PV module will
a.
 destroy the module if the short is not immediately cleared
b.
 have no effect on the module
c.
 destroy the insulation on the module wiring if the short is not immediately cleared
d.
 cause damage only if the module is connected in series with other modules
 

 5. 
If the open circuit voltage of a crystalline silicon PV array is 315 V at 25°C, then, according to the NEC, if the array is operated at -20°C, maximum system voltage must be corrected to
a.
 269 V
b.
 315 V
c.
 369 V
d.
 394 V
 

 6. 
The purpose of the ground-fault protection device in a PV system is to
a.
 reduce the probability of electrical shock to service personnel
b.
 reduce the possibility of fire from an arcing fault to ground
c.
 reduce losses of the PV output energy to ground
d.
 reduce degradation of structural supports from rapid electrolysis
 

 7. 
If the maximum power voltage of a crystalline silicon PV module is 17.1 V at STC, then at 60°C (module temperature) and 1000 W/m2 incident on the module, the maximum power voltage of the module will be closest to
a.
 20.1 V
b.
 17.1 V
c.
 14.1 V
d.
 12.0 V
 

 8. 
According to the National Electrical Code, if flooded lead-acid batteries are chosen for energy storage for a PV system, the battery enclosure must
a.
 have provisions for sufficient diffusion and ventilation of the gases from the battery to prevent the
accumulation of an explosive mixture, and if a tray is used it shall be resistant to deteriorating action by the electrolyte
b.
 have adequate ventilation at the top only, with vent holes screened to keep out bugs and small animals as well as a plastic tray under the batteries to contain spills of electrolyte
c.
 have adequate ventilation at bottom and top, with screened vents and a plastic tray under the batteries to contain spills of electrolyte
d.
 be sealed and insulated so the battery temperature will not drop below 40°F, and have a plastic tray under the batteries to contain spills of electrolyte
 

 9. 
If electronic equipment is to be housed in a container above the battery container with battery cables passing between the two containers, then the batteries should be of what type?
a.
 Flooded lead-acid
b.
 Nickel-iron acid
c.
 Valve-regulated lead-acid
d.
 Any type of nickel-cadmium
 

 10. 
If the electrolyte freezes,
a.
 the battery should be slowly charged
b.
 the battery should not be charged
c.
 the battery should be slowly discharged
d.
 the battery should be heated with a hair dryer
 

 11. 
With the PV array rack mounted at ground level, which would normally be of greatest concern?
a.
 Overheating of the modules
b.
 Electrical hazards from exposed (conductors) open circuit voltages
c.
 Earthquake stresses on the modules
d.
 Physical damage to the array and wiring
 

 12. 
A concern associated with 12-V PV systems that use large wire sizes to minimize voltage drop is
a.
 the difficulty in obtaining dc-rated disconnects with adequate current ratings.
b.
 the possibility of using junction boxes (terminal blocks) or switch boxes that are too small to house the large wire.
c.
 the difficulty in obtaining wire with dc-rated insulation
d.
 the possibility of animals chewing on the wires
 

 13. 
If a proposed PV installation site has an unobstructed south-facing roof area of 60 m2, and if thin-film modules with six watts-per-square-foot power output at STC are to be installed on 50% of the roof, then the maximum available PV array output power (based on the sum of module ratings) at STC will be closest to
a.
 4500 watts
b.
 3600 watts
c.
 2250 watts
d.
 1900 watts
 

 14. 
Which of the following devices does the NEC require to be a part of PV systems mounted on residential dwellings?
a.
 A stand-off mount for the PV modules
b.
 A utility interconnection
c.
 A ground-fault protection device
d.
 An accessible source circuit combiner box
 

 15. 
A crystalline silicon PV array that has bipolar outputs of +252 V and -252 V with a common grounded conductor under Standard Test Conditions is selected for a large single-family residence. The lowest expected temperature at the installation site is -25°C. For this system, the maximum system voltage is closest to
a.
 252 V.
b.
 315 V.
c.
 504 V.
d.
 630 V
 

 16. 
A crystalline silicon PV array that has bipolar outputs of +252 V and -252 V with a common grounded conductor under Standard Test Conditions (STC) is selected for a large single-family dwelling. The lowest allowable ambient temperature in which the system can be installed at a single-family dwelling is
a.
 0°C
b.
 -10°C
c.
 -20°C
d.
 -40°C
 

 17. 
A PV system is to be selected for operating a PV water pumping system. The pump will require 300 W of PV modules for proper operation. A 12 -Vdc model and a 48-Vdc model are available. If both pumps operate at the same power level, the resistance of the wire to the 48-V pump, compared to the resistance of the wire to the 12-V pump, assuming the same percentage voltage drop in the wiring, may be
a.
 1/16th as much
b.
 1/4th as much
c.
 4 times as much
d.
 16 times as much
 

 18. 
A ¼Xx3½  lag screw that has a 3/8 thread is used to attach an L-bracket to an asphalt-shingle roof. If the combined thickness of the L-bracket, shingles, and roof membrane is ¾ inch, and if the screw penetrates directly into a roof truss made of Southern Yellow Pine, into a properly sized pilot hole, then the withdrawal resistance will be closest to
a.
 632 pounds
b.
 773 pounds
c.
 843 pounds
d.
 984 pounds
 

 19. 
Four PV modules, each with an area of 10 ft2, are to be mounted with a stand-off mount that is secured to a metal seam roof with six L-Brackets. If the modules can withstand a load of 75 pounds per square foot, and if it is desired to support the full load with one lag screw in each bracket, and each screw has a withdrawal resistance of 300 pounds per inch including a safety factor of four, the minimum screw thread length that will need to penetrate wood will be closest to
a.
 1.1”
b.
 1.67”
c.
 2.25”
d.
 6.67”
 

 20. 
Stainless-steel hardware is most important in which of the following areas?
a.
 Coastal areas where the air contains salt spray.
b.
 Desert areas where the air contains a mixture of dust.
c.
 Mountainous areas where the solar spectrum contains more ultraviolet rays.
d.
 Inland regions that are subject to freezing temperatures.
 

 21. 
For the situations described, which would result in the most cost-effective use of a two-axis tracking mount?
a.
 In areas of low wind, latitude less than 30°, and moderate daytime summer cloud cover
b.
 In areas of low wind, latitude greater than 30°, and minimal daytime summer cloud cover
c.
 In areas of moderate wind, latitude greater than 30°, and moderate year-around cloud cover
d.
 In areas of moderate wind, latitude less than 30°, and minimal year-around cloud cover
 

 22. 
Referring to Figure 7, if 4 AWG THWN-2 copper wire in a single run of 1.5-inch conduit is used between the array junction box and the source-circuit combiner box, and the wiring from the modules to the junction box is exposed 10 AWG copper wire that enters through a one-inch cord connector at right angles to the 4 AWG conductors, and if the volume of the terminal strip in the junction box is six cubic inches, the junction box must be sized from
a.
 NEC Article 314.16
b.
 NEC Article 314.17
c.
 NEC Article 314.27
d.
 NEC Article 314.28
 

 23. 
The charge controller battery temperature sensor should be connected to
a.
 the side of the battery compartment
b.
 the top of a battery that is at the end of the row of batteries
c.
 the bottom of any battery
d.
 on the side of a battery between two batteries
 

 24. 
Suppose an alternate series three-stage charge controller is available as a backup to a parallel three-stage PV charging source such as a utility-interactive battery-based inverter. Suppose, also, that the PV source is intended to be the dominant charging source. To ensure that the PV source is the dominant charging source, one should
a.
 set the float voltage of the PV charging source higher than the bulk voltage of the alternate controller
b.
 set the float voltage of the PV charging source lower than the bulk voltage of the alternate controller
c.
 set the bulk voltage of the PV charging source lower than the float voltage of the alternate controller
d.
 set the absorption mode time of the PV charging source lower than the absorption time of the alternate controller
 

 25. 
Four 6-volt, 240-Ah batteries manufactured by manufacturer A, and four 6-volt 120-Ah batteries manufactured by manufacturer B are available. It is acceptable to incorporate all of these batteries into a 12-volt PV battery storage bank under the following circumstances:
a.
 If the 240-Ah batteries are connected in 2 series groups and the 120-Ah batteries are connected in 2 series groups, and then the four series groups are connected in parallel
b.
 If the 240-Ah batteries are all connected in parallel, the 120-Ah batteries are all connected in parallel, and then the two parallel sets of batteries are connected in series
c.
 If each 240-Ah battery is connected in series with a 120-Ah battery, and then the four sets are connected in parallel
d.
 There is no acceptable connection of the batteries into a single battery bank
 

 26. 
A good reason for large wire sizes in battery interconnections, even if they are oversized for ampacity, is to
a.
 keep all battery currents as equal as possible
b.
 provide a lower resistance path for battery short circuit currents
c.
 allow for increases in load size or array size
d.
 better secure the batteries in case of high winds
 

 27. 
The purpose of a linear current booster is to
a.
 keep its output voltage the same as its input voltage and boost the output current to a value larger than the input current
b.
 convert a high input voltage and low input current to a lower output voltage and a higher output current
c.
 convert a low input voltage and high input current to a higher input voltage and a lower input current
d.
 keep its output current the same as its input current and boost the output voltage to a value larger than the input voltage
 

 28. 
The purpose of an  inverter is to
a.
 convert dc at one voltage to ac at the same or another voltage
b.
 convert ac at one voltage to dc at the same or another voltage
c.
 convert dc at one voltage to dc at another voltage
d.
 convert ac at one voltage to dc at another voltage
 

 29. 
Sine wave inverters are required for connection to utility lines, because
a.
 they are more efficient than other types of inverters
b.
 they are the only inverters that have low enough harmonic distortion
c.
 only sine wave inverters can be designed to disconnect from the utility when utility power is lost
d.
 non-sine wave inverters cannot develop adequate power for utility interconnection
 

 30. 
A 2500-W inverter is used to supply a 120-V ac load of 1500 watts. This means that the ampacity of the wire at the inverter output must be at least
a.
 12.5 A
b.
 15.6 A
c.
 20.8 A
d.
 26.0 A
 

 31. 
A 2500-W inverter with an input-voltage range of 22 V to 32 V has an efficiency of 88% at full output. This means the maximum inverter input current at full rating will be closest to
a.
 129 A
b.
 100A
c.
 89 A
d.
 69 A
 

 32. 
If the maximum ac output rating of an inverter with 120-V ac output is 1500 W, the rating of the circuit breaker at the point-of-utility connection should be
a.
 15 A
b.
 20 A
c.
 25 A
d.
 30 A
 

 33. 
If the inverter in a utility-interactive PV system begins to hum quietly about five (5) minutes after closing the connection to the utility, then, it is most likely
a.
 working
b.
 overloaded
c.
 connected to a motor load on the utility side
d.
 not working
 

 34. 
Assume a 225-A, 42-position, single-phase, three-wire main distribution panel fed by a 200-A main breaker is used in a dwelling unit. The maximum inverter output current that can be fed to this panel is
a.
 20 A
b.
 25 A
c.
 56 A
d.
 70 A
 

 35. 
The size of the equipment-grounding conductor (type THWN-2) for the PV output circuit should be no smaller than
a.
 14 AWG copper
b.
 12 AWG copper
c.
 10 AWG copper
d.
 8 AWG copper
 

 36. 
A 5-kVA, 120-V generator has a rated output current of 42 A. It does not have a mechanism to limit its output current to the rated value. Assuming they are run in conduit, the output conductors should have an ampacity of no less than
a.
 8 AWG THWN
b.
 8 AWG THHN
c.
 6 AWG THWN
d.
 6 AWG THHN
 

 37. 
A 5-kVA, 120-V generator is used as a backup generator for a system designed with two days of battery storage to 80% depth of discharge. If the generator is sized for charging rate of C/10, and if the generator burns 1 gallon of fuel per hour of run time, the average daily fuel consumption when the generator is the only power source will be closest to
a.
 4 gallons
b.
 5 gallons
c.
 8 gallons
d.
 10 gallons
 

 38. 
If the 5-kVA, 120-V generator is protected with a 50-A circuit breaker, then the equipment-grounding conductor must be no smaller than
a.
 12 AWG copper
b.
 10 AWG copper
c.
 8 AWG copper
d.
 6 AWG copper
 

 39. 
In a PV system, the equipment-grounding conductors should be
a.
 white
b.
 black
c.
 red
d.
 green
 

 40. 
The 2005 NEC allows marking conductors with colored tape, provided that they are larger than
a.
 10 AWG
b.
 8 AWG
c.
 6 AWG
d.
 4 AWG
 

 41. 
The width of the working space in front of an inverter that is 24-inches wide must be at least
a.
 24 inches
b.
 30 inches
c.
 36 inches
d.
 42 inches
 

 42. 
The minimum depth of the working space in front of a charge controller for which the input voltage never exceeds 60 V dc is
a.
 30 inches
b.
 36 inches
c.
 42 inches
d.
 negotiable
 

 43. 
Which of the following items does NOT require UL or equivalent listing?
a.
 the concrete anchors
b.
 the surge protectors
c.
 the battery cables
d.
 the charge controllers
 

 44. 
If 5/16-inch lag screws are used to fasten a charge controller to wooden studs, an appropriate pilot hole size would be closest to
a.
 1/8 inch
b.
 19/64 inch
c.
 7/32 inch
d.
 1/4 inch
 

 45. 
When mounting a heavy inverter or other piece of equipment to a “dry-wall” type of wall, to provide a solid attachment to the wall it may be necessary to use
a.
 thumb tacks
b.
 plastic anchors
c.
 plywood
d.
 moly bolts
 

 46. 
The first step in system checkout after completing the installation is
a.
 test open-circuit voltage
b.
 visually check the entire system
c.
 install the source-circuit fuses
d.
 close all disconnects
 

 47. 
Before applying PV power to either an inverter, a charge controller, batteries or a load, one should first
a.
 check the polarity of the PV output
b.
 install the source circuit fuses
c.
 call the electrical inspector
d.
 close all disconnects
 

 48. 
Assume the STC maximum-power voltage of a crystalline silicon PV array is 68.4 V. If the irradiance is 800 W/m2 and the module temperature is 50°C, assuming the inverter is tracking maximum power with a 1.6% voltage drop between modules and inverter input, the inverter input voltage should be closest to
a.
 68.4 V
b.
 58.9 V
c.
 54.7 V
d.
 47.1 V
 

 49. 
A 4-kWSTC crystalline silicon PV array is operated in a utility-interactive mode with no battery backup. The inverter tracks maximum power, and the array is operating at 50°C with 900 W/m2 incident on the array. There is a 2% power loss in the wiring and the inverter is 94% efficient. On a typical PV system, the inverter output power will be closest to
a.
 3316 watts
b.
 2985 watts
c.
 2612 watts
d.
 1492 watts
 

 50. 
A typical 4-kW crystalline silicon array is operating at STC in a utility-interactive system with battery backup. The STC maximum-power voltage rating of the PV array is 68.4 volts. The system uses a conventional charge controller that does not track maximum power. Wiring losses are 3% and inverter losses are 5%. If the batteries are at full charge at a voltage of 52 V, and if all PV output is delivered to the grid (assume that no power is being used to hold the batteries at 52 volts), the inverter output power will be closest to
a.
 1261 watts
b.
 2207 watts
c.
 2522 watts
d.
 3152 watts
 

 51. 
A typical 4-kW crystalline silicon array is operating at STC in a utility-interactive system with battery backup. The STC maximum power voltage rating of the PV array is 68.4 volts. The system uses a MPT charge controller that has 5% losses. Wiring losses are 3% and inverter losses are 5%. If the batteries are at full charge at a voltage of 52 V, and if all PV output is delivered to the grid (assume that no power is being used to hold the batteries at 52 volts), the inverter output power will be closest to
a.
 1261 watts
b.
 2207 watts
c.
 2522 watts
d.
 3152 watts
 

 52. 
In the event that the utility voltage is lost in a utility-interactive system that has battery backup and an optional standby system ac distribution panel, and if the inverter is programmed in the sell mode,
a.
 the inverter should not supply power to the terminals connected to utility point-of-connection
b.
 the inverter should not supply power to the terminals connected to the optional standby ac distribution panel
c.
 the inverter should not supply power to either set of ac terminals
d.
 the inverter should no longer take dc power from the batteries
 

 53. 
When connecting and disconnecting wires while troubleshooting a PV system, the best way to avoid electrical shock is to
a.
 inspect all questionable terminals, wear rubber gloves and turn off all switches
b.
 keep one hand behind your back, with all switches turned off and only touch grounded surfaces
c.
 turn off switches, measure voltages and currents, and wear protective equipment
d.
 wear shoes with soft rubber soles, turn off all switches, and don’t touch metal surfaces
 

 54. 
If the current in one source circuit is significantly lower than the currents in the remaining source circuits of a PV array, and all modules are in full sun, then without disconnecting any conductors, an appropriate follow-up test is
a.
 measure the individual module currents in this source circuit
b.
 measure the voltage at the inverter input
c.
 measure the short circuit current of this source circuit
d.
 measure the individual module voltages in this source circuit
 

 55. 
A utility-interactive PV system with no batteries consists of 15 100-W modules in series that feed a 1500-W inverter. The inverter output power is found to be 780 W when the modules are operating at 50°C with an irradiance level of 800 W/m2. If three modules are observed to be shaded, which conclusion is most likely?
a.
 The inverter input current is probably too low
b.
 The system is probably functioning properly
c.
 The inverter is probably not tracking maximum power
d.
 The modules probably do not have bypass diodes
 



 
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