### 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

** 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)

{ 18 comments… add one }

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

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.

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?

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..

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

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?….

How many q. on this practice test

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.

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?

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?

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

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

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/

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.

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.

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

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.

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.