PVA practice test
What is the nominal voltage of a lithium-ion battery cell? (not including LFP)
3.6V We do see typical lithium-ion battery cell nominal voltages between 3.6V and 3.8V depending on your source. Also, another popular lithium-ion chemistry is Lithium Iron Phosphate (LFP and the F is for Ferrous, which also means iron). LFP has a nominal voltage of 3.2V. Often times LFP is put in a different category than lithium-ion, however it technically is lithium-ion.
A remote cabin uses the loads below per day, how much total energy is used per day? • 1000W toaster for 6 minutes • 1.2kW hot water heating element for 3 hours per day • Three 17W LED lights for 3 hours per day • iPhone 100 charger at 20W for 3 hours per day
3.9kWh Explanation: Let's do the calculations: Power x Time = Energy, just make sure to get your units right. I am going to convert to kW and hours first to get an answer that is in kWh. You do not have to do it this way, since you can always convert after doing the calculation. Toaster = 1000W = 1kW 6min / 60min/hr = 0.1 hr 1kW x 0.1hr = 0.1kWh Hot water heating element = 1.2kW for 3hr 1.2kW x 3hr = 3.6kWh LED lights 17W / 1000W per kW = 0.017kW 3 lights x 0.017kW = 0.051kW Time = 3hr 0.051kW x 3hr = 0.153kWh iPhone 100 = 20W / 1000W per kWh = 0.02kW Time = 3hr 0.02kW x 3hr = 0.06kWh Sum it all up: 0.1kWh + 3.6kWh + 0.153kWh + 0.06kWh = 3.9kWh
A 4kW PV system with 15% losses in a location with 4.5 sun hours per day, what would be the annual output?
5585kWh 4kW × 0.85 × 4.5 sun hours × 365 days = 5585kWh Losing 15% means keeping 85%, which is where the 0.85 derating factor comes from. Always think about what you keep. With this kind of question, look at the information that you are given and then make logical use of the information. Do not get distracted if you see a derating factor that you are not used to.
What is the maximum voltage of dc PV circuits permitted on 1 and 2 family dwellings?
600V PV system dc circuits are permitted to be up to 600 volts on 1 and 2 family dwellings according to NEC article 690. Dc circuits on buildings other than 1 and 2 family dwellings are permitted to have a maximum voltage up to 1000 volts and can be up to 1500V when not on buildings.
An off-grid installation has a 1HP pump that is on 10% of the time and a 20W light that is on 100% of the time. What is the energy use per month?
68kWh 1HP = 746W 746W × 0.1 × 24hrs × 30 days = 53,712Wh 20W × 24hr × 30 days = 14,400Wh 53,712Wh + 14,400Wh = 68,112Wh 68,112Wh/1000 = 68kWh NABCEP requires you know that 746W = 1 horsepower (HP). Often pumps are rated in horsepower. These are typical load energy calculations and you should be comfortable converting units and performing energy calculations when given power and time.
A 50kW interactive PV system has 15% system losses in a location getting 5.4 peak sun hours per day average throughout the year. What would be the expected annual energy output?
83,768 kWh We are given some data and need to use it in a logical way. All the data we are given is relevant. Often, we are given irrelevant data that we have to sift through. The Math: If we lose 15%, then we keep 85% 100% - 15% - 85% 50kW x 0.85 = 42.5kW after losses 42.5kW x 5.4 PSH = 229.5kWh/day 229.5kWh/day x 365 days = 83,768 kWh per year
A 100kW STC PV system with 8% system losses, using PV that is +3 − 0% production tolerance, a 95% efficient inverter, what would be the expected ac output if 1000W/m2 irradiance?
87.4kW to 90kW 100kW × 0.92 × 1 × 0.95 = 87.4kW 100kW × 0.92 × 1.03 × 0.95 = 90kW For +3 - 0% production tolerance the derating factor is 1 to 1.03. Many designers only look at the low end of the tolerance and would just give you the answer of 87.4kW, but if an answer has a range, go with both sides of the range for the correct answer
Which of the following is an example of a diversion load?
A water pump filling tanks on a stand-alone system when the battery is charged and there are no other significant loads requiring electricity. A diversion load (sometimes called a dump load) is when you divert excess electricity to a load that is not critical. Three examples of the more common diversion loads can be a water pump filling a tank, a heating element in a hot water tank or a heating element heating your home. Sometimes people will just dump the extra electricity by converting it to heat outside. Just imagine that your batteries are full, and you would like to still make use of your PV array, rather than not producing power. (Not producing power with a PV system is sometimes called curtailment). Here is an example of one use of a diversion load in an ac-coupled stand-alone (off-grid) PV system. You have a battery connected to an inverter that makes an ac microgrid of sorts. You then connect interactive inverter to the ac side of that battery inverter along with all of your loads (things that use electricity). When the battery is charging, it often goes through different stages of charging where the battery cannot accept the full power of the array, but partial power of the array, depending on the battery technology and sometimes with a fully charged lithium battery, no power from the array. Lead-acid batteries on the other hand always like a least a trickle charge. With some ac-coupled systems the only way to control the interactive inverters (which are connected to PV and not the battery) is by frequency regulation. What will happen is when the batteries reach a certain level of charge, then the inverter connected to the battery will change the frequency so that the interactive inverters will anti-island (turn off). Interactive inverters, unless programmed specially will always produce as much power as they can. Since in this situation, since we cannot throttle down the interactive inverters, we can instead have a diversion load that will take power out of the system when the batteries need less power to charge than the array has to offer. Some people consider the grid to be a type of diversion load when you have a grid-tie battery backup PV system. After a power outage, the PV will have the first priority to charge the batteries and then as the batteries cannot accept the full power of the array, the excess power will be diverted to the grid. solarsean.com solarsean.com 22 This explanation has been on the more advanced side for this class and if you feel comfortable with this explanation, you may be a good candidate for the NABCEP PV Installation Professional Exam. For a simpler explanation, just remember that a diversion load will take extra power when the batteries can accept no more.
Which code or standard is used for calculating building structural loads?
ASCE 7 ASCE is the acronym for American Society of Civil Engineers An integral part of building codes in the United States, Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE/SEI 7-16) describes the means for determining dead, live, soil, flood, tsunami, snow, rain, atmospheric ice, earthquake, and wind loads, and their combinations for general structural design. Structural engineers, architects, and building code officials will find the structural load requirements essential to their place.
Concentrated PV
Only works with direct sunlight Concentrated PV only works with direct sunlight. Also concentrated PV usually works with 2-axis trackers that always point at the sun and will not work at all during cloudy conditions. We need direct sunlight, so we can focus sunbeams to make concentrating solar technologies work. Many people confuse concentrating PV with concentrating solar thermal. PV is converting sunlight directly to electricity, whereas thermal is working with heat. Concentrating PV is very rare, especially since solar cells have gone down in price over the last 2 decades. Concentrating solar thermal is not as rare, but not common.
What is a primary factor(s) in performing wire sizing calculations?
Temperature and ampacity In order to perform wire sizing calculations, you need to know the current, the ampacity (ability of the wire to carry current), the ambient temperature, which we often get from www.solarabcs.org/permitting and how many conductors are together in a raceway. Having more conductors together in a small place causes the wire to hold onto heat.
Where can you find the requirements for rapid shutdown of PV systems on buildings?
NFPA 70 NFPA 70 is also called the National Electrical Code (NEC) and 690.12 is where you find the rapid shutdown requirements.
What is the C rate of a 100Ah battery at 5A?
0.05C or C/20 0.05 because at a discharge rate of 5A only 0.05 of the 100Ah battery would be discharged in 1 hour
A 12V light is left on for 13 hours at 1.5A with a 12V battery. How much energy is used?
0.234 kWh 12V × 1.5A × 13hr = 234Wh 234Wh/1000 = 0.234kWh
How long do PV module manufacturers generally warranty their modules for?
10 years for material and 25 years for performance Most PV manufacturers offer a 10 year warranty for materials and a 25 year warranty for performance. Sometimes you will see numbers slightly higher than this. The material warranty, in my opinion, is more important, since that is often where your problems would be if you ever had any, such as the connectors falling off or the bypass diodes breaking. PV, as long as it is put together right, performs well beyond the performance warranty specifications for decades, as far as we can tell. Oftentimes performance warranty will warranty performance above 80% of STC values for 20 years. Something has to be really wrong if a PV module will work at less than 80% power.
What power percentage of PTC is STC?
108% : I looked at the datasheet of a typical crystalline solar module and the STC rating was 260W, while the PTC was 240W. STC/PTC = 260W/240W = 108%
What is the best voltage for charging a 12V lead-acid battery?
14.1V Best voltage for charging a 12V battery is 14.1V (best of the choices given). A 12V lead-acid battery will sit charged at 12.6V and often charge somewhere between 14 and 15V. If a 12V lead-acid battery is at 50% depth of discharge, it will measure about 12V. Note: for a 3.6V lithium-ion battery cell, you may be charging at 4.2V. 3.6V here is the nominal voltage and 4.2V the charging voltage
Which is the smallest conductor?
18 AWG 18 AWG is the smallest conductor. From small to large the conductors listed are 18AWG, 10AWG, 0 AWG, 3/0 AWG. 0 AWG is also called 1/0 AWG. Most of the world does not use AWG (American Wire Gauge) wire sizes and uses a very simple to understand system. Most of the world uses the crosssectional area of a conductor in square millimeters. For example, a 10AWG wire is 5.26 mm2
If a 12V PV module has 36 cells, then how many volts is a 54-cell module?
18V 12V / 36 cells = 0.333V/cell 0.333V/cell × 54 cells = 18V
A 12V light is left on for 13 hours at 1.5A with a 12V battery, how many Ah are used?
19.5 Ah 1.5A × 13hrs = 19.5 Ah
What do you often see in a solar service agreement (SSA) to ensure system performance?
1:4 A solar service agreement can be a power purchase agreement (PPA) or a solar lease. As for ensuring performance, remote monitoring is very important. If you want to go beyond the scope of this exam and course, you may learn more about this at: https://www.greentechmedia.com/articles/read/why-solaras-a-service-is-not-going-away-anytime-soon Be aware that this article was written by a solar financial service provider, which may have opinions in it. I have always liked them. (There is another type of service in electrical terms that you should know and that is an electrical service, which is where the utility "serves" you electricity, through the "service conductors".
What is the proper slope of an extension ladder?
1:4 slope is required for a ladder according to OSHA. This means that for every 1 unit of distance towards you, the ladder will go up 4 units of distance. Many people that use ladders say that if you are standing with your feet at the base of a ladder and put your arms straight in front of you, if they touch the ladder, that is about a 1:4 slope. Note: If you use the length of the ladder from where it touches the ground to the roof for the "4" part of 1:4 that is what it says in the OSHA regulations, but most tests have it the other way, but the difference in the angle of the ladder is very small. This part of the triangle is called the hypotenuse.
If a PV module produces 350W at Standard Testing Conditions and the dimensions of the PV module are 998mm wide and 1681mm long, what would be the efficiency of the PV module?
20.8% Efficiency of a PV module is determined by comparing how much power the module puts out in watts per square meter and comparing that the STC power going into the module during testing, which is 1000W per square meter. The Math: Size of PV module in square meters: Convert mm to m 998mm = 0.998m 1681mm = 1.681m Length x Width = Area 1.681m x 0.998m = 1.68 square meters Power per area calculation: 350W / 1.68 square meters = 208W/square meter Compare to STC irradiance: 208W / 1000W = 0..208 Turn into percentage: 0.208 x 100% = 20.8% efficient PV
Standard Testing Conditions (STC) temperature is:
25C Cell Temperature STC is 25C cell temperature, 1000 watts per square meter irradiance and 1.5 Air Mass. You should know this by memory. Note: All other testing conditions (such as NOCT, PTC and PVUSA) temperature is 20C ambient, which is actually a hotter cell temperature than 25C, since the cells will often heat up around 30C hotter than ambient when in the sun.
What would be the most practical way to add battery backup to an existing gridtied system?
Ac-coupled If you have an existing interactive inverter, you can keep your same PV system and then add batteries, switch around some loads that you want to backup to a subpanel and then add a battery inverter for ac-coupling. This way you do not have to replace your existing inverter and re-design your PV system. It is also possible to do whole-house backup without using a subpanel, however with these systems, either the battery cost is huge, or your battery will often go dead soon after the power goes off. Those selling dc-coupled solutions would argue that dc-coupling is more efficient, since you are not going from dc PV to ac and back to dc in the battery. However, there are complicated answers that ac-coupling manufacturers will argue. I prefer to remain neutral as an educator. Note: In the future the terms ac-coupled and dc-coupled may be changed to acinterconnected and dc-interconnected on NABCEP exams to follow the 2023 NEC terminology. This is not something to worry about at the moment, but something to keep in mind. The PVA exam has very little focus on the NEC. NABCEP currently uses the 2017 NEC. Do not let this concern you, just study the current practice exams and whenever NABCEP changes, we will change the practice exams. We will make big announcements when NABCEP announces any changes.
A PV system that uses an interactive PV inverter and a battery inverter is called:
Ac-coupled system A PV system that uses an interactive (grid-tied) inverter and a battery inverter is called and ac-coupled system. If you have a battery that is connected to PV via ac, then it is ac-coupled. A dc-coupled system on the other hand will have only a battery inverter and it will also have a charge controller, which is connected to the PV. Or the battery inverter and charge controller can be in one unit. The charge controller function can also be shared by an energy storage system and inverter. A hybrid system will have PV and then another source of energy besides the utility or batteries. The most typical hybrid application is having a backup generator on a stand-alone (off-grid) system. A bimodal inverter (more commonly called a multimode inverter) is an inverter that has an output that will anti-island (interactive inverter output) and an output that will work in island mode (power stand-alone loads). Note: In the future the terms ac-coupled and dc-coupled may be changed to acinterconnected and dc-interconnected on NABCEP exams to follow the 2023 NEC terminology. This is not something to worry about at the moment, but something to keep in mind. The PVA exam has very little focus on the NEC. NABCEP currently uses the 2017 NEC. Do not let this concern you, just study the current practice exams and whenever NABCEP changes, we will change the practice exams. We will make big announcements when NABCEP announces any changes.
Which of these are required parts of a personal fall arrest system?
Anchorage, lifeline, connector, body harness Personal fall arrest systems are used limit the length of a fall to minimize injury from falling from a working level. They consist of anchorage, connectors, and a body harness. Lifelines are themselves a type of connector which attach the body harness to the anchorage point, but other types of connectors such as D rings or carabiners may be used to attach lifelines to the anchor or the body harness. Anchors must be secured to a point capable of supporting at least 5000lbs per person attached to the anchor.
How often should an employer evaluate a safety program?
Annually At the OSHA website below, you can read in the second sentence that the employer shall evaluate the safety program at least annually. You can read about it here: https://www.osha.gov/safety-management/program-evaluation Obviously, you can evaluate more often than that, but who is going to reevaluate their safety plan every 30 seconds?
There is a system with 4 concrete pavers (weights) securing it on a rooftop. What kind of system is this?
Ballast rack mount A ballast is something with weight and a ballasted PV system uses weight, rather than penetrations to hold PV down. A ballasted system often has a rack, so a ballast rack mount is the best answer. A standoff, is an alternative to a ballasted system and standoffs are sometimes fastened to rooftops to secure racks with penetrations.
Why is it important to install a dc combiner box according to manufacturer's instructions?
Because it is listed for use this way Anything that is UL listed was tested to the listing using the manufacturer's instructions. You should always install listed equipment according to the manufacturer's instructions. A combiner box is a sort of a junction box. In the earlier days of solar, installers would make their own combiner boxes out of junction boxes, terminals, busbars and fuses. I have never heard of dc rated wire. Wire does not care if the current is dc or ac. The language of the answer d is confusing and does not make as much as answer c.
Which is the best solution of the following for multiple orientations when designing a PV system?
Microinverter A Microinverter will do maximum power point tracking on a PV module level, so that the PV source circuit is one module. Every module will work independently. Dc-to-dc converters (power optimizers) can also have maximum power point tracking on a PV module level. Note: It is possible to have 2 or 3 modules in series with a microinverter, which may be more common in the future. Some microinverters can work with 4 modules, which are not in series and each have their own MPP.
Microinverters connected together in a cable are best called a
Branch Microinverters are connected together in parallel, in a cable, which is electrically much the same as when you have a few plug sockets on your living room wall that share the same circuit breaker. When you have a load or loads, including outlets in a wall, connected to a circuit breaker, it is called a branch circuit. Microinverters are almost the same thing, except instead of being loads, they are sources. Many solar professionals call the microinverter circuit a branch. This is often wrongly confused with PV modules and dc-to-dc converters (optimizers) connected together in series (not parallel). A string is a term solar professionals often use to indicate a series connection and microinverters are connected together in parallel, not in series.
Which is an NRTL?
CSA NRTL stands for Nationally Recognized Testing Lab and the NRTLs most often used in the PV industry in the US and Canada are UL (underwriters laboratory), CSA (Canadian Standards Association), TUV (German language acronym), Intertech and a few others. To research the list, do a search for NRTL and OSHA. You can find the NRTLs for different products listed at the OSHA website. NRTLs are not just used to list renewable energy system equipment, but many different things, such as your computer and your TV. You can often see the different listings written on small print on your things. It is interesting that our PV equipment needs to be UL listed, so UL makes up the test, however there are other organizations besides UL that can perform the UL tests. UL sells instructions how to do the test for a high price. Sounds monopolistic to me. In China, where many things are manufactured, there is a big testing lab industry. In order to sell PV in the US, testing has to be done to UL standards. People buying PV in a small country in Africa may ask for UL or CE (European standard) listed equipment even if it is not required, to ensure quality. When large solar farm contracts are drawn up, there are often more testing requirements than just UL. Large multi-billion-dollar PV factories often have UL testing done onsite.
Maintenance of sealed valve regulated lead-acid batteries includes
Cleaning terminals On a sealed lead-acid battery (also known as maintenance free), one does not have access to the electrolyte fluids. Equalization is not done on sealed batteries, since equalization requires distilled water to be added to the battery. All batteries can have their terminals cleaned.
What is the most important and safest measurement to take before disconnecting PV Modules at the MC connector?
Current Using a clamp-on ammeter that measures dc current lets you see if there is any current without touching any wires and is very safe. Many clamp-on ammeter's only measure ac current and some measure both dc and ac. Most PV module MC connectors are disconnected with voltage present, so measuring voltage will not tell us if there is dangerous current going through the circuit. If there is current, there can be an arc when disconnecting. If there is voltage alone, then there should not be an arc when disconnecting. Often the connectors are marked "do not disconnect under load", which means current is present. If you did measure energy or power, you would have to measure current and voltage at the same time, and measuring voltage at a connected MC connector is not done and measuring voltage requires touching live parts with your multimeter probes.
The definitions of the difference of a PV output circuit (circuit coming out of a dc combiner) and inverter input circuit for a grid-tied system are very similar and some believe overlap. In many diagrams, what is the point where the PV output circuit becomes an inverter input circuit?
DC disconnect Often times on diagrams, a PV output circuit goes from a dc combiner to a dc disconnect and then from the dc disconnect to the inverter it is labeled as an inverter input circuit. Both of these circuits will carry the same current. Note: NABCEP is not yet using the 2023 NEC, however the 2023 NEC removed the term PV output circuit.
Interactive inverters come with
Dc ground fault protection Most PV systems are required to have dc ground fault protection for the solar array. Interactive inverters are connected to the solar array, so they will have the dc ground fault protection. If you had a dc coupled system using a charge controller between the battery and the PV array and the inverter, then the charge controller is where you would find the dc ground fault protection. The NEC exception to the dc ground fault protection is when you have one or two PV source circuits (strings) not on a building. You would not be able to find an interactive inverter without dc ground fault protection. It is possible to find a charge controller without dc array ground fault protection. If you had a ground fault on the ac side, then the inrush current would come from the utility and that ground fault would be cleared by the ac circuit breaker or fuse, just like with a typical ac appliance. PV arrays also have dc arc fault protection requirements usually done on the string level. There was at one time something in the NEC about PV ac arc fault protection, but that was removed, because it was difficult to accomplish by the circuit breaker manufacturers for backfeed currents. Arc flashes are dangerous, however if there were an arc flash, it would likely open the circuit with an explosion. There is no arc flash detection equipment on inverters. Arc flash protection is typically the gear that you wear when working in dangerous conditions, such as with high voltage switchgear. Not something an entry level solar installer would come into contact with. There has been, according to rumors, a mystery arc flash question on the advanced NABCEP PVIP exam.
How to reach optimum voltage for each module
Dc-to-dc converter With a string inverter, the voltage is that of the string and not an individual module. Connecting modules in series adds each module voltage to the string voltage. A charge controller often has more than 1 module in series, so in that case you would not always have module level "optimum" voltage. A pulse with modulation (PWM) charge controller is either a cheap charge controller or an old charge controller. PWM is an alternative to MPPT (maximum power point tracking). MPPT will keep the voltage at its optimal spot on the IV curve and PWM will just open and close the connection between the battery and the PV really fast in order to slow down the charge. The nominal voltage of the battery and the PV have to match with PWM. Dc-to-dc converters will do MPPT on a module level, so the voltage and current parameters you would see on an IV curve are optimized for each individual module. Note: Some dc-to-dc converters can take more than one module in series. It is probably going to be more common in the future to see two- or even three-module dc-to-dc converters.
Undersized PV array
Decreases battery life Decreased array size decreases battery life (due to not charging battery fully). Not fully charging a lead-acid battery often is not good for the battery. This is not the case for lithium-ion batteries. Lead-acid batteries get lead-phosphate crystals building up on the plates when they do not receive a full charge often.
Name for the type of monetary charge from the utility for the most power a customer has used in a 15-minute interval for that billing period.
Demand charge Most utility charges are for energy used. Demand charges are a charge for power. Remember that energy is over time and power is all at once (rate). Demand charges are usually for places like businesses which use large amounts of power at a time such as a factory turning on all lights and machines when a shift starts. Because the utility must always be ready to provide the power needed by the customer, they sometimes charge a fee for the most power used in that billing period. Often the utility uses 15 minute intervals to bill the customer for the most power used in any one interval in that month. Because demand charges often happen during times when PV is not producing, solar alone will not usually help lower demand charges. Batteries, however, can help reduce demand charges by providing power when a large amount of power is needed so, not as much power needs to be drawn from the utility.
What is a tax benefit for a business when deducting expenses for durable goods and equipment such as PV systems?
Depreciation A deduction lowers your net income, so you pay less taxes. Depreciation is like a deduction, but it is based on the loss of value of something often over years
What is the main purpose of a diversion charge controller?
Divert current from the battery to specific loads A diversion charge controller will take PV energy and when the battery is already charged more than it would need from the full PV array power, some or all of the power from the array will be directed to the diversion load, rather than overcharging the battery or just curtailing the PV array. Curtailing means turning off or reducing power from the array. A diversion load is often a water pump or a heating element in a hot water heater.
Which of the following will show system components and connections?
Electrical diagram Electrical diagrams such as single line diagrams and 3 line diagrams are plans showing the electrical components and connections that will be part of the system. Electrical diagrams are usually required as part of the permitting process and interconnection agreement.
What part of the permit process addresses manufacturers' warranties?
Equipment specifications There is typically no requirement by the building department to address manufacturers warranties, however it is common that the AHJ will want to see the PV module datasheets and inverter datasheets, which do usually have information about the manufacturer's warranty on them. Some people buy used PV at low prices that do not come with a warranty, and there is no NEC rule against not having a manufacturer's warranty at all. Sometimes rebate programs will have rules against using used equipment, because in the past when PV was really expensive there were some unscrupulous PV installers who would install a PV system, get the rebate and then remove the same system to get the rebate in another place with the same PV.
Which of the following types of safety equipment will prevent a fall from a roof?
Fall restraint A fall restraint system is designed to prevent falls while a fall arrest system will not necessarily prevent a fall but is designed to minimize injury in the event of an accidental fall. Fall restraint and fall arrest systems are both comprised of anchors, connectors, lifelines, and harnesses or body belts and work in much the same way. Even fall arrest systems should limit the total length of a fall to 3.5 feet or less so the difference between the 2 types of systems is minimal but sometimes they like to throw in a few pretty specific OSHA related questions. If you plan on continuing on to any of the other NABCEP Certifications, most will require you complete an OSHA training program so, it could be helpful to spend a little time checking looking through some OSHA resources if you have time. Here is a way to remember this. If you get arrested, you were stopped after you already started the crime. Fall arrest stops you after you already started the fall.
How can you ensure that you do not void the warranty of a tile roof when installing a PV system?
Follow instructions provided by roof manufacturer With a tile roof, just like with any roof, you need to follow manufacturer's instructions in order to not avoid warranty. There may be different warranties involved, such as the roof, the PV and the racking system. Walking on the supported part of the tile is something that roofers are experts at, but always look for the warranty question to have a follow manufacturer's instruction kind of answer.
How do you ensure module manufacturer warranty is not voided?
Follow manufacturer installation instructions PV modules and other equipment were listed and tested according to the manufacturer's installation instructions and the warranty is voided if you do something that is not according to those instructions. The test that UL does is unknown by most and usually only manufacturers purchase the expensive UL testing requirements. If an AHJ tells you to install something in a way that is not according to manufacturer's instructions, then the warranty could be voided. We shall always install according to the NEC, however the NEC is a required code and not a recommendation and is not what will void the warranty or keep the warranty intact.
Which of these would cause an interactive inverter to turn off for safety?
Grid is out Interactive inverters are inverters that are connected to the grid and are capable of exporting power to the grid. When the grid goes out interactive inverters will anti-island, or disconnect from the grid, to protect workers that may be working on the utility wires during the outage. Clouds and warm temperatures both may cause the inverter to output less power and work less efficiently but should not cause an inverter to shut down for safety reasons. Having a relatively high PV to inverter ratio is a good thing for inverter efficiency. Typically, a ratio of around 1.25 kW of PV to 1 kW of inverter power works well to make sure the PV is producing enough to keep the inverter output close to its maximum efficiency and to get your money's worth out of your inverter and ac components. If there is way too much PV to inverter the inverter the inverter will not be able to use all of the potential power produced by the PV. That would be a waste of PV in some cases, but the inverter will only use as much as it is rated for so having a high PV to inverter ratio is not dangerous. Some people use a PV to inverter ratio as high as 2:1. This can also be called an ILR for inverter load ratio. When the PV could have produced more with a larger inverter, we call that missed power "clipping". It is often considered a good design to allow for some clipping.
To ensure electrical safety, which of the following should be done first?
Identify all power sources Remember as we said before in these exam explanations, that it is safer to look before you touch, so identifying all power sources is probably safer than opening disconnects. With a PV system, it is possible to have another energy storage system, a utility connection, old lead-acid battery system, etc. Take a good inventory of what you are working with, check the grounding system, see what is turned on or what is turned off. Look for wires that are missing insulation, look for squirrels or pigeons. Look for duct tape on a sloppy installation. Be aware of things that look out of place. See if the PV circuits are going through a puddle. Then after your visual inspection, you can also check for currents with a clamp on ammeter without touching anything. Then you can open the disconnects. It is possible that there could be a ground fault and if the grounding system was not fastened correctly, you could still get shocked after everything was turned off by touching the metal ac or dc disconnect box. Remember open means off.
The maximum power point is the place on the IV curve where these two parameters intersect.
Imp and Vmp Imp x Vmp = power and the MPP is the place on the IV curve where these two parameters intersect. Voc is turned off and Isc is shortened out, which are two places on the IV curve where there is no power.
Where should you direct a pyranometer to get the most accurate irradiance reading for your array?
In the plane of the array To find the irradiance that is reaching your array it is best to direct the pyranometer at the same direction and angle that your array is facing. When commissioning a system you will want to compare the actual production that you see on monitoring of the system to the expected output of the system. To find the expected output of the array you will need to know the derating factors to find what percent efficiency you should expect out of the array. One of the derating factors to consider is the actual irradiance reaching the array compared to the irradiance used in STC which is 1000W/m2 . By measuring the irradiance in the plane of the array with a pyranometer and dividing that number by 1000Wm2 you find the irradiance derating factor. Your irradiance is always better when facing the sun and it is extremely rare that a PV system is directly facing the sun, unless it is using a dual-axis tracker, which is expensive and also rare. If you want to see if your PV is operating properly, point the pyranometer in the same direction as the PV. Large expensive solar farms will also take different irradiance readings, besides the plane of array (POA), such as straight at the ground for albedo, on the back of the PV for bifacial readings on the back of the PV and horizontal (flat).
What is the scope of the NEC?
Installation and removal of conductors, equipment, and raceway Below is quoted from the NEC and if you read it, it pretty much gives you that a is the answer. Answers c and d would have more to do with UL listing of equipment. 90.2 Scope. (A) Covered. This Code covers the installation and removal of electrical conductors, equipment, and raceways; signaling and communications conductors, equipment, and raceways; and optical fiber cables for the following: (1) Public and private premises, including buildings, structures, mobile homes, recreational vehicles, and floating buildings (2) Yards, lots, parking lots, carnivals, and industrial substations (3) Installations of conductors and equipment that connect to the supply of electricity (4) Installations used by the electric utility, such as office buildings, warehouses, garages, machine shops, and recreational buildings, that are not an integral part of a generating plant, substation, or control center (5) Installations supplying shore power to ships and watercraft in marinas and boatyards, including monitoring of leakage current (6) Installations used to export electric power from vehicles to premises wiring or for bidirectional current flow
Which PPE should be used when working at voltages over 600V?
Insulated gloves Proper gloves should be used. A lifeline is the only other PPE on the list and a lifeline is part of a personal fall arrest system (PFAS) and should be used when working where you can fall over 6 feet. Often when working over 600V, someone is on the ground level.
Which building codes will be used in residential construction and adopted much like the NEC?
International Residential Code Most states adopt the International Code Council (ICC) codes (often called the building codes), which are not as international as they sound, since they are primarily used in the US. Here are the ICC Codes that most often used by solar professionals: IRC = International Residential Code is used for most dwellings. IBC = International Building Code is used for larger buildings. IFC = International Fire Code is to prevent fires, however the IRC is intended to be a stand-alone code, so it can be argued that the IFC does not apply to residential. Some states, such as Florida, adopt the NFPA-1 Fire Code rather than the IFC. They are very similar and it is just political.
Which code must be complied with for PV installs?
NEC Article 690 NEC (National Electrical Code) Article 690 Photovoltaic Systems contains the electrical installation rules used for PV systems in the USA and other places. The other articles of the NEC must also be adhered to in the NEC. For instance, Article 705 Interconnected Power Production Sources is used when connecting to the utility and Article 310 Conductors for General Wiring is used for wire sizing of PV systems. The NEC is also known as NFPA 70. The International Electrotechnical Commission (IEC) is an international standard and is not intended to be a code that is followed like a rule book, such as the NEC. UL 1741 is the standard for testing electronic equipment used in PV systems, such as inverters. IEEE (Institute or Electrical and Electronics Engineers) is also a standards organization.
A stand-alone PV system will work in this mode:
Island A stand-alone system is a system that works without the grid, which means it can be an island of power and work in island mode. Inverters working in island mode are regulating their own voltage, and the current is adjusted as the loads need it. Interactive inverters are also known as grid-tie inverters and will anti-island when the grid goes down, which means they will disconnect from the grid when there is no grid (primary power source). Inverters working in interactive mode use grid voltage and usually put out as much current as possible. (They can also limit current in some cases, such as is done with non-exporting PV systems in Hawaii). A multimode inverter is an inverter that will work in island mode or interactive mode. The best answer is a. Island mode. Advanced discussion (most people should skip this): Note that some high-level people will differentiate island-mode and stand-alone mode, where stand-alone means not ever connected to the grid and island means that can connect to and disconnect from the grid. I am only mentioning this, in case someone is high-level here, but this will probably not help you on the PVA exam. Another advance thing is you will sometimes see people talking about standalone energy storage being connected to the grid without solar. This standalone is usually without the hyphen. This is usually only talked about with large utility-scale energy storage projects.
Which of the following is the best way to compare the feasibility of different energy systems?
LCOE If you are comparing different energy systems, such as solar, wind, coal, nuclear and solar plus storage, the best way is to calculate the levelized cost of energy (sometimes called levelized cost of electricity). This is comparing the energy price after all is done and includes maintenance, project costs and everything. LCOE is the lifetime costs divided by the energy produced. ITC is the investment tax credit and is the main incentive for solar in the US. It does not directly help when comparing solar to other energy sources, which do not have an ITC. The ITC does help PV have a lower LCOE in the US. Price per watt is one way people price PV systems. Price per watt for residential solar in the US is about 3 times as much as utility scale solar. Price per watt does not take into consideration if the PV system is installed with a lot of shade or in a cloudy place, so it is not a good metric for calculating the value of the system when compared to other systems.
Bypass diodes
Limit effects of shading Bypass diodes reduce effects of shading and are wired in parallel in cells in the junction box on the back of the PV module
Stand-alone inverter output goes to
Loads Off-grid inverter output goes to loads. Loads are what use electricity.
Which level has the authority over enforcement of the NEC usually?
Local The Authority Having Jurisdiction (AHJ) that usually interprets the NEC and approves the permits is the local city or county building department. There are some exceptions, such as when doing a project on a federally owned property, you may have the federal government being the AHJ. Also, in some cases, such as a mobile home, you may have the state as the AHJ. Check your local rules. The NFPA just writes the NEC and does not enforce it. You could also say that the utility is the AHJ when it comes to the interconnection. Here is from the NEC: 90.4 Enforcement. This Code is intended to be suitable for mandatory application by governmental bodies that exercise legal jurisdiction over electrical installations, including signaling and communications systems, and for use by insurance inspectors. The authority having jurisdiction for enforcement of the Code has the responsibility for making interpretations of the rules, for deciding on the approval of equipment and materials, and for granting the special permission contemplated in a number of the rules.
A roof has a 2.5:12 slope. What kind of roof is it?
Low slope A roof with a 3:12 slope or less is considered a low-slope roof. Sometimes a slang term for a low-slope roof is a flat roof, however there should be no roof that has zero degrees slope, since it will not drain properly.
What is the function of a current transformer?
Measure current A current transformer (CT) is a small type of transformer that is placed around a conductor to measure its current. CTs are commonly used to measure solar production and energy consumption of residential or commercial buildings. They are required for energy storage systems when you want to prioritize use of the onsite solar energy production such as when there are utility feed-in restrictions and time-of-use rates. They may be required for performance based incentives or power purchase agreements (PPAs) to ensure the most accurate reporting of production and use. GFCIs also work by using CTs to detect differences between the input current and the current returning on the neutral line. If the current leaving the source and returning to source are not the same that indicates some of the electrons have taken a different path through a fault to ground. Another term used in place of current transformer is current transducer (CT).
What is the best tool for measuring wire insulation:
Megohmmeter Mega is the prefix for a million and we want our wire insulation to approach infinite resistance, so no current leaks through. Nothing is perfect, so millions of ohms is as close as we can get to infinity. Other names for a megohmmeter are insulation tester, insulation resistance tester and Megger (brand). An ohmmeter is the next best guess, but it is probably not sensitive enough to catch a small flaw in the insulation of the wire. Also, a digital multimeter usually has an ohmmeter built into it.
A supply-side connection will have the PV interconnection between the __________ and the __________.
Meter, main breaker A supply-side connection (aka source connection to a service or lineside tap) is made between the meter and the main breaker. This is always on the utility side of the first overcurrent protection.
Which is the best order of steps to complete before removing equipment during troubleshooting and maintenance.
Open ac and dc disconnects, isolate equipment, test voltages Ac and dc disconnects that are load break rated disconnects should be opened first since they are safe to open while under load. After those disconnects are open there is no current, then and can isolate equipment by opening the nonload break rated disconnects such as touch safe fuse holders or connectors between modules. Before removing any equipment, you should test voltage and current to make sure that everything was opened and isolated properly. You should not replace fuses before confirming the source of the problem has been corrected. Replacing a fuse before the problem has been corrected will result in a recurrence of the issue and could be a fire hazard, so if your fuse has blown, figure out why it blew before replacing the fuse (use common sense).
Microinverters are connected between the ________ and the _______.
PV module, service panel Microinverters (and other inverters) are between the PV and the service panel.
Which of the following would be considered a dead load on the roof of a building?
PV modules and racking A dead load is considered to be a permanent weight on the structure. All of the other answers would all be considered live loads because they are not constant throughout the life of the building. Dead load = Permanent Live load = Temporary
In order of most to least efficient, which is the best producer of energy?
Pole mount, ground mount, BIPV Think of airflow dissipating heat here. The most airflow will be on a pole mount, since the PV is sticking up in the air on a pole. The reason that pole mounts are rare is because they are more difficult to engineer than ground mounts (more likely to tip over) and the benefits of airflow do not outweigh the drawbacks. Building integrated PV (BIPV) on the other hand, which is PV built into the roof typically has little to no airflow and will have the worst airflow (unless you talk to a BIPV salesperson... haha). A ground mount is usually going to have airflow close to a pole mount, so that would come in second. There are several types of roof mounted systems here besides the BIPV. A flush mounted system is the most common for residential sloped roofs. These types of systems are usually on a rack and about 6 or so inches above the roof, with some room for the electronics, racks and wires. These systems have better airflow than BIPV, but worse than most others. Ballasted rooftop PV systems are common on commercial low slope (flat) roofs and usually have better airflow than flush mounted systems, however sometimes they will have wind deflectors that interrupt the airflow with the intention of preventing the wind from going up under the system and blowing it off the roof. With a greater wind and more uplift forces, it would take a greater ballast (weight) to hold it down and some roofs cannot take the extra weight, especially in areas where it snows.
Best sealant for residential rooftop
Polyurethane Polyurethane and silicone can both be used as rooftop sealants, but polyurethane better than silicone and is considered the best sealant for residential roofs.
Wind uplift forces in the construction industry in the US are measured in
Pounds per square foot Wind uplift is measured in pounds per square foot (psf) in the US.
An agreement in which a third party developer installs, owns, and operates a PV system on a customer's property and the customer purchases the energy produced by the system at an agreed upon rate which is generally lower than the rate of the utility.
Power Purchase Agreement Power Purchase Agreements (PPA) and solar leases are similar and provide most of the same benefits. The main difference between PPA and a lease is with a PPA the customer is purchasing power from the system owner at a specific rate (usually per kWh similar to how they would have been billed by the utility) and in a lease the customer is renting the system at a specific monthly payment. Both PPA and leases make solar accessible to customers who may not be approved for other financing or are not able to afford the large down payment typically required to purchase a system and both usually lower the amount the customer pays for electricity each month.
A typical interactive PV system will NOT.
Power a remote cabin isolated from the grid When you read a question like this, always pay close attention to a word like NOT. Typical residential interactive systems will: Reduce greenhouse gasses Reduce fossil fuel use Reduce air pollution Most interactive inverters do not power grids when the grid is down. Interactive means interactive with the utility, so if there is no utility, you probably will not have an interactive inverter. Note: Ac coupled PV systems do have interactive inverters and battery inverters that can work together without a utility, but this is not your average system.
Units for irradiance are
Power per area Irradiance is power per area, usually measured in watts per square meter. 1000W/m2 is the irradiance level called "peak sun" or irradiance at Standard Test Conditions. Energy per area is irradiation or insolation.
What is the NEC for?
Practical safeguarding of persons and property Here is the explanation of what the NEC is for right out of the beginning of the NEC: NEC 90.1 Purpose. (A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity. This Code is not intended as a design specification or an instruction manual for untrained persons. Practical safeguarding of persons and property does include installation of conductors, PV systems and interconnections, but the NEC is not an installation manual. The NEC is not concerned about efficiency, just safety.
Why do we need to know the lowest expected temperature?
Prevent over voltage Lower temperatures cause higher PV voltages. If the location gets very cold, we will not be able to connect as many modules in series as if we were in a location that never was cold. You can put more modules in series in Hawaii than you can in Alaska.
Which of the following must be included as part of an emergency action plan for OSHA?
Procedure for reporting of fires This is another OSHA requirement question you could be asked about. OSHA requires employers to have emergency action plans in place in case of an emergency in the workplace. An emergency action plan must include procedures for emergency evacuation and plans for reporting a fire or other emergency as well as employee training on the procedures. Just by
What is NOT an example of a typical performance-based incentive?
Rebate When a question uses NOT in a context like this, it is time to be careful and pay attention to what the question is asking (test psychology). This means that there are 3 things that are performance-based and one thing that is NOT performance-based. It is nice of the test writers when they capitalize NOT, so you do not miss the NOT. An SREC is a solar renewable energy certificate and is a common solar incentive on the East Coast in places such as NJ and MA. For each 1000kWh (1MWh) that the PV system generates, whether you export it or use it, you will have 1 SREC. The utility has a quota of SRECs to meet and has an incentive to buy the SREC from you. To learn more, go to www.srectrade.com. This is a performance-based incentive based on how much energy your PV system produces. A feed-in-tariff (FIT) is not unheard of, but uncommon in the US. There was a great FIT program in Ontario Canada in the years around 2010 that gave people with PV systems smaller than 10kW, 80.2 cents per kWh for 20 years! This was unrelated to, if they were using electricity, and the rate was about 10 times what they were paying for electricity. The FIT system was first invented in Germany and started the modern solar industry around the turn of the millennium. This is based on performance of the PV system. Net-metering is the main incentive for installing non-utility scale PV in the US. We get credit for exporting electricity to the grid and get to use that credit anytime in the year. We can make extra in the summer and use that credit in the dark of winter or on summer nights when there is no sun. At first with net-metering we would get full credit for the value of the energy we exported. As the solar installed gets greater on the grid, we are seeing netmetering export rates become less than what we pay for electricity. This is because if everyone had solar, then utilities would go broke and we don't want those beloved utilities to go broke, do we? There have been rebates that were performance based, but most rebates were not performance based, so the best answer is rebate. Rebates are much less common than they used to be and were usually on the state level.
. What is the most common maintenance of an array on a business's existing roof over the life of the system of the following
Removal of system for re-roof of building Oftentimes a roof needs to be replaced under a PV array. In some cases, the solar installer will include it in the contract. A smart buyer will ask to make sure that removing and re-installing the PV once during the life of the system is included.
Which of these environmental factors will have the greatest effect on a ballasted PV system on a flat roof?
Seismic loads While environmental temperatures can have significant effects on system design and production it is unlikely that daily temperature fluctuations are extreme enough to cause major issues if the yearly extreme temperatures were considered during the design process. PV is made to work in the sun all day long. Part of the testing for UL listing of PV modules includes impact from hail so modules should not receive significant damage from most hailstorms, but it could with Texas sized hail. Hail would affect all PV and not especially ballasted PV. Depending on the region where the system is being installed the potential for seismic loads could affect how much weight can safely be added to a roof. Earthquakes can affect ballasted systems more than other types of PV systems. Seismic refers to earthquake forces for those of you who are not in California or Hawaii. You will see some questions that we think are not perfect and perhaps this is one of them. Always take the best educated guess for success.
For a supply-side connection, the output of the inverter is limited by
Service entrance conductor ampacity Supply side inverter output is limited by the service entrance conductors. The loads are already protected from the utility by the main service disconnect (main breaker) and you are connecting to the supply-side (utility side) of that main breaker. Note: Other terms for supply-side connection are source connection to a service (2023 NEC) and line-side tap (slang).
A performance guarantee is:
Something that can be spelled out in the fine print of a solar service agreement, such as a PPA or a solar lease and often tells a minimum of how much energy you should expect from your system. A performance guarantee is based on what a PV system will produce and not to be confused with a solar module warranty. This performance guarantee may also depend on ongoing operations and maintenance (O&M) from an approved provider. If you do not have your modules washed in a dry dirty area, how can you expect them to perform?
What does a hydrometer measure?
Specific gravity of battery acid A hydrometer measures specific gravity of battery acid. The specific gravity of water is defined as 1 and a fully charged battery has a specific gravity of about 1.265. A hydrometer looks a bit like what is known in some circles as a turkey baster. Hydro = fluid Meter = measure
Which is a self-commutated inverter?
Stand-alone inverter Self-commutated definition: A commutation where the commutating voltage is supplied within the inverter. On the other hand, you can have a line commutated inverter where the line voltage will commute or turn off the inverter. Self-commutated is a stand-alone island mode and a line commutated inverter is an interactive or anti-islanding inverter output circuit. Trick: think of the word self and a PV system that works by itself is selfcommutated. Inverters that work off-grid keep a relatively constant voltage and inverters that work with the grid (interactive) send current into a grid that already has voltage.
An Array in Sacramento California in August (hot and dry) is not producing as expected. Which of the following is NOT a likely problem?
String size too long Late summer in Sacramento is hot and can be dry. When it is hot, voltage can be low. Too long of a string would be a problem when it too cold, not hot. Soiling could be a problem, since in a dry place, there can be dust without rain to wash it away. Pay attention to the word NOT in a question. Also, since there are 2 answers that are opposites, there is a good chance that one of them is the correct answer
Voltage drop of conductors is based on:
The length and diameter of the conductor Voltage drop is calculated by using ohm's law, which states V=IR. To determine V for voltage drop, we will need to know the current and the resistance of the wire I. To calculate R, we need to know the properties of the conductor. A thicker wire has less resistance (better for carrying current) and a shorter wire has less resistance that a longer wire. To reduce voltage drop, someone should reduce the length or increase the width of the wire. A more advanced topic is voltage drop percentage and this topic is not needed to answer this question. Voltage drop is how much voltage you lose on a wire. Voltage drop percentage is calculated by determining how much voltage you lose to: how much voltage you have. A lot of times PV systems have somewhere in the neighborhood of 1 to 3% voltage drop percentage, which means they are losing 1-3% of their power due to voltage drop (wire loss). As PV modules go down in price, it is more reasonable to save money on wire and have more voltage drop. Also, recall that Volts x Amps = Watts, so a decrease in voltage drop percentage is the same as power loss percentage. Using a transformer to increase voltage, while decreasing current is another strategy for decreasing voltage drop and voltage drop percentage. High voltage and low current has less power losses, but has a tendency to be more sparky.
When installing a ballasted PV system on a low slope roof, which is of greater concern to the AHJ?
The touching of dissimilar metals The AHJ is the Authority Having Jurisdiction and this acronym is used so much in the industry, that you should know it. The AHJ is usually the local building department. They are concerned with safety and not performance. Shading, PV module orientation and airflow under PV modules are all important for performance, but they are not safety issues. Having dissimilar metals come into contact with each other is a safety issue. For instance, copper should not be fastened to aluminum. If this happens you will have galvanic corrosion and the aluminum will corrode. This is the same chemical process of how a battery works, except with the batteries that we use, they can be recharged. When we attach a copper wire to an aluminum rail or ballast tray, we will attach them via an intermediary, which is not going to corrode, such as stainless steel or a tin-plated copper lug.
Which happens with heat?
Thermal expansion and decreased PV voltage Heat decreases PV voltage and since voltage x current = power, heat decreases power and since power x time = energy, heat decreases energy and money. Heat also causes thermal expansion, which means that rails and conduit can expand and get longer when it is hotter. Higher elevations are usually colder and also higher elevations have less atmosphere, which causes less filtering of light and can increase current, power and energy.
What is the main function of the Authority Having Jurisdiction?
To check Code compliance The inspecting and permitting agency, often referred to as the AHJ, will check to make sure that the solar plans and building of the solar system is done so that everything will adhere to the local Codes and standards.
What would be an engineering decision to use wind deflectors on a ballasted PV system?
To reduce required ballast weight Most ballasted systems are on low slope (flat) commercial rooftops. A wind deflector on a ballasted system is sometimes added so that the wind is less likely to lift up the system and we can then put less ballast weight to hold the system down. Many of these systems are designed in wind tunnels to be more aerodynamic and I have seen a ballasted PV system that mostly survived the eye of a hurricane! Especially in areas with snow, we have a concern with extra weight on the roof. In fact, in areas with snow there can be rare years when there are unusually high amounts of snow and people have to shovel off the roof to prevent collapse. These systems will almost always require a structural engineer's stamp in order to add PV. A byproduct of the wind deflector is that it will decrease the airflow and cause a slight decrease in voltage than without a wind deflector, which is a disadvantage, since voltage x current is power and power x time equals energy and energy is money!
Specification found in PV module installation manual
Torque for mounting Torque (how much pressure you tighten a screw, nut or bolt with), is a specification that should be in an installation manual. You may also have the other information in the installation manual, such as which region to mount the PV in, how to clean it and your maximum wind speed. I would pick torque for a specification, since it is the best answer, however like with many test questions, there can be other answers that can be argued, but torque in my opinion is the best answer
With a working, power-producing inverter with 4 PV source circuits, you put your current measuring clamp around each individual PV source circuit and discover that one of the PV source circuits (strings) does not register any current and the others do register current. What should be done first in order to troubleshoot this problem?
Turn off the inverter and disconnect the strings The safest thing to do here is to turn off the inverter first and then to disconnect all of the individual strings. With a test, always think of the safest thing to do first. First you look at things without touching them, then you turn things off before you touch wires. Short circuiting strings does not sound like a good idea. Sometimes strings can get short circuited through a dc disconnect when advanced commissioning of an array is done, but this is not common and could cause arcs if you just took the MC4 connectors and short circuited a string that way. If you accidentally did short circuit an array by connecting all of the MC4 type connectors together in a loop, then you should then wait for dark night to set in before opening that circuit. It is not a good idea to work on a string, while the other strings are producing power. The electricity from the working strings could possibly go back into the nonworking string. In fact, the non-working string could have a direct short from the other string in this scenario of one string not working.
In jurisdictions where class A fire rated roofing is required, what classification must PV modules have to be installed on buildings?
UL 1703 or 61730 and Class A Roofs are classified for fire resistance as Class A, Class B, or Class C. Class A is the most fire resistant. Some jurisdictions especially where wildfires are common may require roofs to have a Class A fire rating. When a specific fire rating is required for roofing, the PV modules must have the same rating or better. The testing for PV module fire rating is done as part of the UL listing for the module. The UL listing for PV modules is 1703 (or 61730) so the classification required for a module being installed where class A roofing is required is UL 1703 or 61730 and Class A.
What is the UL standard for PV modules?
UL 1703 or UL 61730 UL listing is done for much of the PV equipment. Here are the listings as follows: UL 1703 or UL 61703 = PV UL 1741 = Inverters, charge controllers, dc-to-dc converters, combiners. UL 2703 = Racking (PV mounting systems) UL 3741 = Rapid Shutdown Systems UL 9540 = Energy Storage Systems (there are other Energy Storage and battery UL listings) Note that there are different rules requiring UL listing. For instance, you always have to use UL 1703 (or 61730) PV and UL 1741 inverters in the US and Canada, however you do not have to use a UL 3741 Rapid Shutdown System, it is just one way of complying with rapid shutdown requirements. Also, you are not required to use a UL 2703 racking system and you can build your own, but most AHJs will require an engineer to approve of your home-made racking design, which would be expensive, since you are hiring an engineer to do calculations and analysis.
The interconnection of a PV system is approved by
Utility Interconnection is approved by the utility. They are who you are connecting to.
If installing a stand-alone 120V inverter using 120/240V distribution equipment what type of labelling is required?
Warning not to connect multiwire branch circuits Multiwire branch circuits cannot be used when using inverters that only produce 120 Volts. Systems that can produce 120 and 240 volts have 2 lines which are out of phase with each other so the currents on the neutral wire balance each other out. Systems that only produce 120 Volts do not have 2 out of phase lines so if a multiwire branch circuit was connected there would be an excess of current on the neutral wire which could potentially start a fire. Article 710 in the NEC about Stand Alone Systems tells us it is ok to use 120/240 service panels and subpanels with 120V inverters as long as we us a warning label that tells us not to use multiwire branch circuits. This is not a very common situation, but something you can be familiar with before taking your NABCEP exam. Think...120V inverter will probably require the "no multiwire branch circuits" sign, since you would be hard pressed to find 120V service equipment in the USA. 120V inverters are more likely to be used on small off-grid (stand-alone) systems.
What is the most likely maintenance to have to be done within the first 5 years of a PV installation?
Washing the dust and pollen It is inevitable that there will be pollen &/or dust on a PV array. In some locations it is worse than others, such as the western part of the US, where it does not rain for months at a time. That being said, many people never wash their PV. This can be because they can accept the losses in production vs. the hassle of washing the PV. They may install 10% more PV to make up for the losses. Replacing broken bypass diodes is not common. If the diodes break during the first 10 years that the PV module was installed, then it is likely that the module could be replaced under the materials part of the warranty. It is not as likely to see broken glass on a PV module, than it is to wash it during the first 5 years. The glass on a PV module is very strong and if the glass does break, you do not replace just the glass, you will have to replace the entire PV module. Many solar installers have had squirrels and pigeons under their arrays and there are guards that can help keep the critters out. It is still much more common for people to have to wash the PV. I live in a place where squirrels are on the trees every day, but have never seen any evidence of them under the array. In different regions, this can be different and in New York, for instance they are more famous for squirrels liking PV arrays. No matter where you are, your PV array could use a wash once in a while.
Which is the most important safety requirement for checking voltage?
Wear proper PPE It is always important to wear proper PPE while performing any job. Although the other answers could be correct, they are looking for the best answer. This is a tricky one so let's go through why we choose D over the other options.
Which of the following is true about PV wiring of single conductor cable under a PV array?
Wiring should be secured at least every 4.5 feet 2017 NEC or 24" 2020 NEC Depending on which version of the NEC being used the answer for this question may be different but we should still be able to determine the correct answer from these choices. According to NEC 690.31, exposed PV wiring should be held up off of the roof using clamps or cable ties. This is true in 2017, 2020, and 2023 versions of the code. The distance allowed between clamps or ties could be either 2 feet or 4.5 feet depending on the code being used though. The 4.5 feet was for the 2017 NEC and earlier and the 2 feet was new in the 2020 NEC. As of this writing, NABCEP is still using the 2017 NEC.
The reduction in solar module output caused by normal wear and tear and exposure to UV rays is referred to as?
performance degradation Solar modules slowly degrade at a rate of about 0.5% - 1% each year over the life of the module. Probably closer to 0.5% (or less) these days. This is called performance degradation and is usually the longest part of the PV module warranty, such as for 25 years.
How far above the roof should an extension ladder be?
≥ 3ft An extension latter, which is often used to climb onto a roof should be at least 3 feet above where it contacts the roof. It should also be at a 1:4 slope meaning for every 4 feet of height, it should come back 1 foot. This is the greater than symbol: ">" and the is the greater than or equal to symbol: "≥". C being the right answer means that the ladder must be greater than or equal to 3 feet above the roof.
