NABCEP Sample Exam Questions

 

Q1: An insolation measurement takes into account these factors:

a. solar power, unit area

b. solar energy, unit area

c. solar efficiency, unit area

d. solar power, time

 

Q2: All of the following reduce or enhance solar irradiation received at a particular location except:

a. Module Efficiency

b. Ozone

c. Earth’s position in relation to the sunday

d. Altitude

Q3: What is the maximum number of series connected Kyocera KC200GT (Vmp= 26.3) modules that would be in the operating range of the SMA 2500 U inverter? Assume STC conditions.

a. 18

b. 19

c. 22

d. 23

 

Q4: Your customer’s solar array has 12 Kyocera KC85T modules arranged in 2 series of 6 modules per each string. Which of the following do you expect to see as the output parameters under STC conditions?

a. 43.4 volts @ 32.04 amps

b. 104 volts @ 10.04 amps

c. 130.2 volts @ 10.68

d. 34.8 volts @ 30.12 amps

Given:

Kyocera KC85T module

Vmp=17.4

Imp=5.02 Amps

 

Q5: The highest average winter insolation will fall on a solar module with a tilt angle equal to :

a. The location’s latitude minus 15 degrees

b. The location’s latitude

c. The location’s latitude plus 15 degrees

 

Q6: You are trying to determine the cause of a PV system failure.  Which of the following would you check last?

a. Blown Fuses

b. Bad Connections

c. Tripped Breakers

d. Shorted Solar Cells

 

Q7. If the open circuit voltage (Voc) of a crystalline silicon PV array is 315V at 25° C (STC), then, according to the NEC (National Electric Code) chart, if the array is operated at -20° F, maximum system voltage must be corrected to

a. 269 V

b. 315 V

c. 382 V

d. 394 V

 

Q8: In order to determine the expected maximum PV array voltage, the module voltage at Standard Test Conditions must be corrected for

a. The highest expected solar insolation at the installed location

b. The lowest expected solar insolation at the installed location

c. The highest anticipated air temperature

d. The lowest anticipated air temperature

 

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 ANSWER KEY:

Q1: An insolation measurement takes into account these factors:

a. solar power, unit area

b. solar energy, unit area

c. solar efficiency, unit area

d. solar power, time

 

Q2: All of the following reduce or enhance solar irradiation received at a particular location except:

a. Module Efficiency

b. Ozone

c. Earth’s position in relation to the sunday

d. Altitude

Q3: What is the maximum number of series connected Kyocera KC200GT (Vmp= 26.3) modules that would be in the operating range of the SMA 2500 U inverter? Assume STC conditions.

a. 18

b. 19

c. 22

d. 23

Hint:

600 V inverter max/26.3 Vmp = 22.8 =22 modules (ROUND DOWN)

Q4: Your customer’s solar array has 12 Kyocera KC85T modules arranged in 2 series of 6 modules per each string. Which of the following do you expect to see as the output parameters under STC conditions?

Given:

Vmp=17.4

Imp=5.02 Amps

a. 43.4 volts @ 32.04 amps

b. 104 volts @ 10.04 amps

c. 130.2 volts @ 10.68

d. 34.8 volts @ 30.12 amps

Hint:

amps= 5.02 times 2 strings in parallel= 10.04

volts= Vmp 17.4V times 6 modules in each string =104.4

 

Q5: The highest average winter insolation will fall on a solar module with a tilt angle equal to :

a. The location’s latitude minus 15 degrees

b. The location’s latitude

c. The location’s latitude plus 15 degrees

 Hint:

The sun is lower in the sky, so to create a more perpendicular angle, you increase the angle (from horizontal)

Q6: You are trying to determine the cause of a PV system failure.  Which of the following would you check last?

a. Blown Fuses

b. Bad Connections

c. Tripped Breakers

d. Shorted Solar Cells

Hint:

The AC panel and shutoffs should be checked first, often this resets due to lightning or simple problems.

 

Q7. If the open circuit voltage (Voc) of a crystalline silicon PV array is 315V at 25° C (STC), then, according to the NEC (National Electric Code) chart, if the array is operated at -20° F, maximum system voltage must be corrected to

a. 269 V

b. 315 V

c. 382 V

d. 394 V

Hint:

Change -20° F to -28.9°C (-29), use temp correction factor 1. 21,  387.45= 381.15V  from  table NEC 690.7.  See below for chart.

 

Q8: In order to determine the expected maximum PV array voltage, the module voltage at Standard Test Conditions must be corrected for

a. The highest expected solar insolation at the installed location

b. The lowest expected solar insolation at the installed location

c. The highest anticipated air temperature

d. The lowest anticipated air temperature

Hint:

Temperature correction factors are used because at cooler temperatures voltage of a PV module spikes, and you could potentially over power your inverter.   Correct for these low temperatures using coefficients from  table NEC 690.7.  –See below for chart with Answers.

Temperature Correction Factor

% Change in module maximum power voltage (Vmp) as a function of cell temperature=

  • [(operating cell temperature C° - 25°C) x (-0.5%/C°)]

National Electric Code Table 690.7 (2011)

 

 

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29 Responses to “NABCEP Sample Exam Questions”

  • Arnol Tolbert on December 8, 2009

    i’m taking entry test this saturday 12/12/09.. do you have any further sample questions or study guides.

  • Arnol Tolbert on December 8, 2009

    i’m taking NACEP entry test saturday 12/12/09.. do you have any other sample questions or study guides… thanks in advance

    Arnol tolbert

  • Mark on February 24, 2010

    Is this sample exam for the NABCEP PV entry level COK? or the PV entry level installers exam?

  • admin on February 24, 2010

    Hey Mark, It is for the Entry Level COK.

  • MarkC on April 23, 2010

    I think the answer posted for question #3 is wrong. 23 modules times 26.3 volts Vmpp equals 604.9 which is over the 600 volts max. The correct answer should be 22 modules which gives an acceptable 578.6 volts.

  • admin on April 23, 2010

    What you have here, seems right. I’ll have to look it up…seems like there was a reason I rounded up.

  • Seth on May 13, 2010

    question # 8.

    When I use the formula to change F to C, I get -28C. This number doesn’t correspond to the correction factor of 1.17. It corresponds to 1.25. Please explain. What am I doing wrong?

  • admin on May 13, 2010

    I think you are referring to Q7. I think you are right and I have updated this–good catch. The main idea of this question is to always check and make sure you are using the right kind of degrees, C or F.

  • Chris on June 3, 2010

    On Q3 how did you come up with 600 volts max on the inverter? An SMA 2500 is 600vmax but a Fronius 2500 is 500vmax.

  • admin on June 7, 2010

    The 600 volt max is a given for that kind of inverter. Just as a Fronius 2500 volt max is 500. (it will usually be given in the question).

  • Tim on August 8, 2010

    Q-4 OK, 6x,s 17.4 = 104.4 the Amp’s remain at 5.02 times 2 strings 10.4 “But” NEC requires 5.02 times 2 strings, for 10.4 x 1.25 X 1.25 total of 16.25 Amps. so the correct ans/ would be 104.4 Volts @16.25amps..

  • Tim on August 8, 2010

    Q-6 On a Grid interactive system, a power failure will cause a shut down.To prevent Islanding. again,.refer to NEC

  • Tim on August 8, 2010

    Q-8 In order to determine the “Expected Max PV Voltage” The max STC must be corrected for: should be A/D A gives the max power per/hr under STC at the install location and (d) colder air temp will increase voltage with reduced resistance affected by ambient air temp. So.. What am I missing here?….

  • admin on August 8, 2010

    Temperature Correction Factor chart on table NEC 690.7 (which is in the study guide and formulas article), to correct the lowest temperature anticipated.

  • admin on August 8, 2010

    Is this an added factor per string?

  • marty on August 14, 2010

    How many q. on this practice test

  • marty on August 14, 2010

    im getting ready to take a 10 week class to help prepare for the entry level exam. wondering how many Questions will be on the test.

  • admin on August 15, 2010

    60 multiple choice http://greencredential.com/nabcep-entry-level-certificate-exam/

  • Kemal Betin on December 2, 2010

    Hello
    Thanks for posting these questions.
    1 ) Do you think we have to memorize formulas such as temperature coefficients for Module Power/Voltage/current, like we need for Q7 ?
    2 ) Do they allow us to bring a cheat sheet to the exam?

  • Gail Burrington on December 11, 2010

    Here’s some of my thoughts on some items under discussion. In Q3, NEC says that Voc is used to calc. Vmax, so 18 is best answer; Q4 asks for expected parameters ( as in being measured) so the deratings used for “edge of cloud” and safety factors in wire and OCPD planning should not apply..; Q7, with NEC 2008(used for exam),now has 1.23 factor in table 690.7; but I really appreciate the sample Q.s, those taking the recent exam seemed to do more poorly than previously..any thoughts?

  • Eric S. on December 14, 2010

    how many of this question are on the test? and where can i get the actual study questions for the test?

  • admin on December 14, 2010

    There are 60 questions on the test.

  • elias taweh on January 5, 2011

    can they be specific which book or books we have to study for the entry level exam

  • PRKR on January 6, 2011

    These are the most common text books http://greencredential.com/solar-textbooks/, but they cover more information than necessary.
    The Green Credential study guide has just the info regarding the NABCEP Entry Level exam and can be purchased here: http://greencredential.com/nabcep-study-guide/

  • George Horrocks on January 27, 2011

    I was going to let it go, but there are just too many fundamental errors here to let it pass.

    In Question#3, you refer to a discontinued SMA 2500 inverter and “operating range”. Operating range by definition is not the maximum voltage necessarily, but the MPPT voltage, as indicated on data sheets by Solectria Renewables, SMA, and others. The word “range” is only used in conjuntion with MPPT voltage – not max and min or strike voltages. Since you are using Vmp, the module operating or maximum power point voltage, you should obviously use the inverter operating range. And you really should update to use a currently manufactured inverter, or use a fictitious one entirely. The 2500 had an MPPT voltage of 234-550V (@240V), so 550/26.3 = 20.9 AND YOU ROUND DOWN, so the correct answer is 20. We would only use Vmax of 600V, if you were given Voc – which is really the only thing that is critical – assuming a single string.

    On Question#4, Tim says that NEC says we should correct with the 1.56 factor, but that is just WRONG. The question is not what should we select for overvoltage protection, but what we would expect to see (or measure) at STC, so the answers are straight multiplication for 104.4V @ 10.04A.

    In the first Question#6 (yes there are two), of the available choices, ONLY #d is correct – the Breaker is tripped – and ONLY, if we are connected to the grid with a load side connection – downstream from the backfeed breaker and/or the main breaker. There are lots of other good answers, but none are listed – as pointed out, the utility grid could be down, a separate AC disconnect (as required in many jurisdictions) could be off or if fusible,its fuse(s) could be blown, etc. In the second Question#6, you indicate that the answer is that one of the fuses is blown, but that is only true if there are two fuses – what if there are four fused strings and you have 50% output, then answer “a” would not be correct. BUT, if you had a poorly designed system, and a particularly hot summer, the strings could be undersized, and even though you had very sunny weather, the string voltage might drop below the minimum operating voltage required by the inverter. If it did this half the days of the month, you would have 50% production, even though NO fuses were blown.

    In Question#7, you are using NEC 2005′s Table 690.7, which is not used for the NABCEP exam currently. The NEC2008 Table has greater granularity, so the correction factor at -28.9C (-20F) would be 1.21, not 1.25, for an answer of (315 x 1.21) 381.15VDC. Question#8 should really not refer to the “module voltage”, but the open circuit voltage, otherwise the question is really just vague. But the answer is still only “d”, not “a” at all. We are talking STC and STC defines the intensity of the sunlight as 1000W/m2, so “a” does not apply – the insolation is already corrected for STC.

    Whew! It is important to get the basics right, so we don’t have a lot of uninformed installers giving the industry a bad name.

  • Drew on April 29, 2011

    I was looking at this because I took the NABCEP PV entry level test yesterday. These questions are at the right level for the entry level test.

  • victor on May 24, 2011

    in question # 7 if the array is at 25 degrees celcius at (STC) acording to N.E.C. 690.7 correction factor -20 must be 1.18 and not 1.25, 315 v x 1.18 =371.7 v and not 393.75 v

  • gary on May 22, 2013

    Are these real questions from real exams? I have a few issues.

    Question #2: What is “the sunday?” Is that a typo?

    Question #7: -20F = -29C. According to your chart, that is a 1.21 factor. That should be 381.15 V.

  • PRKR on May 22, 2013

    Gary,
    not a typo, you know you can eliminate the obviously wrong answer. I corrected number 7, think the 1.21 correction factor is correct and I updated the question 5-22-13. Thanks for commenting.

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