NABCEP’s Solar PV Installer Exam is notoriously hard.

Here are 50 practice questions to help you pass.

NABCEP Certification Exam Prep
1. NEC section ________ shows the requirements for working spaces
around live electrical equipment?

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NABCP Certification Exam Prep
1. Answer:

110.26

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NABCEP Certification Exam Prep
2. What is the maximum latitude at which the sun can achieve a
90º altitude angle?

a. 30.45º

b. 23.45º

c. 18.45º

d. 40.45º

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NABCEP Certification Exam Prep

2. Answer:

b. Approx. 23.45º north and south of the equator, but like magnetic
declination, the latitude of the Tropics varies over time.

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NABCEP Certification Exam Prep
3. If the open circuit voltage of a polycrystalline silicon PV module
is 37.0V, the module Vmp is 29.9V, the inverter max voltage is
600VDC and its MPPT voltage range is 300 to 480VDC, and the
minimum temperature is -24°C. What is the maximum number of
modules per source circuit according to the NEC? List the NEC
section where the answer is found.

a. 11
b. 14
c. 13
d. None of the above

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NABCEP Certification Exam Prep
3. Answer C:

37V x 1.20 = 44.4V

600V max ÷ 44.4V = 13.4 → 13 modules

NEC Table 690.7 – 1.20 correction factor

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NABCEP Certification Exam Prep
4. A PV array of Suniva 300 Watt modules consists of 3 rows
and 10 columns of racked modules mounted in landscape and
facing south at latitude 30°. The modules are tilted at 20⁰. The
mounting posts are installed 3 ft. deep. How long must the
posts be? Module dimensions are 77.6” x 38.7”.

a. 94.05”
b. 62.54”
c. 75.7”
d. 39.7”

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NABCEP Certification Exam Prep
4. Answer

Answer: C
Sin(angle) = opposite ÷ hypotenuse

Sin(20⁰) = Height ÷ 38.7” x 3

Height = sin(20⁰) x 116.1”
Height = 0.342 x 116.1” = 39.7 ”
39.7” + 36” = 75.7”
for your test with Sea

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NABCEP Certification Exam Prep
5. An array located at 30⁰N latitude consists of two rows racked facing
south. Both rows are on a level surface and the height from the
ground to the highest point on the module is 39.7”. Calculate the
minimum distance in feet needed between rows so the modules will
not be shaded at 9AM on December 21. Use the sun chart provided.

10
Dr. Sean White teaches HeatSpring’s NABCEP Prep Course.
Study for your test with Sean: http://bit.ly/NABCEPprep

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NABCEP Certification Exam Prep
5. Answers:

a. 103.3”
b. 8.6’
c. 9’
d. 5.7’

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NABCEP Certification Exam Prep
5. Answer: b

Tan(angle) = opposite ÷ adjacent where opposite is array height and

adjacent is row-to-row spacing

Tan(21°) = 39.7“ ÷ Row-to-row

Row-to-row = 39.7" ÷ 0.384
Row-to-row = 103.4“ or 8.6’

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NABCEP Certification Exam Prep
6. At 43⁰ North latitude on the winter solstice, the solar altitude
angle at noon is____.

a. 43⁰
b. 23.45⁰
c. 90⁰
d. 70.45⁰

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NABCEP Certification Exam Prep
6. Answer:
d. 23.55⁰

90° - 43° (latitude) + (-23.45°) = 23.55°

For the Summer Solstice, the third number is +23.45°C, resulting in

70.45°.

For either equinox, the last number is zero.

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NABCEP Certification Exam Prep

Dr. Sean White teaches HeatSpring’s NABCEP Prep Course.

Study for your test with Sean: http://bit.ly/NABCEPprep

16
NABCEP Certification Exam Prep
7. An array is comprised of 22 modules. Each module is 64.5” x 38.7”
and weighs 44.1 lbs. The site will experience 50 psf. of uplift force.
What is the approximate total uplift on the array?

a. 48,000 lbs.
b. 19,000 lbs.
c. 13,000 lbs.
d. 16,000 lbs.

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NABCEP Certification Exam Prep
7. Answer:
a. 19,000 lbs.

64.5” x 38.7” ÷ 144 sq. in/sq. ft. = 17.33 sq. ft.

17.33 sq. ft. x 22 modules x 50 psf = 19063 lbs.

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NABCEP Certification Exam Prep
8. What is the temperature correction factor if the module correction
factor is -0.335 %/⁰C and the cell temperature is 54⁰C?

a. 0.903
b. 1.181
c. 1.097
d. 0.819

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NABCEP Certification Exam Prep
8. Answer:
a. 0.903

1 + (-0.00335 x (54 – 25)) = 0.903

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NABCEP Certification Exam Prep
9. A module has dimensions of 64.5” x 38.7” and is in a landscape
orientation on a flat roof. The position of the sun at 9am on Dec 21 is
11° elevation and 130° azimuth. What is the maximum tilt angle the
modules can have so that there is no inter-row shading. A 2 foot
walkway is required between adjacent rows?

a. 10°
b. 15°
c. 20°
d. 25°

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NABCEP Certification Exam Prep
9. Answer:
a. 10° is the closest to 10.8°

Module width x SIN(tilt angle) = module height

Module height x COS(azimuth angle) ÷ TAN(elevation angle) =

minimum row spacing

The azimuth angle is 180 – 130 = 50°

The height is 24” x TAN(11) ÷ COS (50) = 7.26”
SIN-1(7.26” ÷ 38.7”) = 10.8° tilt angle

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NABCEP Certification Exam Prep
10. Where no overcurrent protection is provided for the PV dc circuit,
an assumed overcurrent device rated at the PV circuit Isc is used to size
the equipment grounding conductor in accordance with NEC ____.

a. Article 250.122
b. Article 250.66
c. Table 250.122
d. Table 250.66

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NABCEP Certification Exam Prep
10. Answer:
c. Table 250.122

NEC Article 690.45(A) refers to Table 250.122

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NABCEP Certification Exam Prep
11. There are to be two critical loads on a PV system. Your
analysis shows that one uses 1900 Wh/day and operates for 6 hrs.
per day and the other uses 1200 Wh/day and operates for 3.5 hrs.
What is the weighted average operating time?

a. 4.9 hrs./day
b. 5 hrs./day
c. 9.5 hrs./day
d. 5.3 hrs./day

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NABCEP Certification Exam Prep
11. Answer: b. 5 hrs./day

(1900 Wh/day x 6 hrs.) + (1200 Wh/day x 3.5 hrs.)

= 5 hrs.
(1900 Wh/day + 1200 Wh/day)

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NABCEP Certification Exam Prep
12. What is the combined effect in wattage of the 2 loads in the
previous question?

a. 3500 Watts
b. 620 Watts
c. 140 Watts
d. 1.9 Watts

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NABCEP Certification Exam Prep
12. Answer: b 620 Watts

(1900 Wh/day + 1200 Wh/day)

= 620W
5.0 hrs.

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NABCEP Certification Exam Prep
13. The critical design month is the worst case scenario where the
load and the _____________ are used to design the PV system.

a. Peak demand
b. Total power demand
c. Duty cycle
d. Insolation data

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NABCEP Certification Exam Prep
13. Answer: d. Insolation data

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NABCEP Certification Exam Prep
14. Active means of charge control is required by the NEC
unless the maximum array charge current for 1 hour is less than
____ % of the rated battery capacity measured in amp/hours.

a. 1
b. 3
c. 5
d. 10

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NABCEP Certification Exam Prep
14. Answer: b. 3%

See NEC 690.72

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NABCEP Certification Exam Prep
15. When battery temperature is high, temperature compensation
________ the VR set point to minimize the excessive over
charging and reduce electrolyte losses.

a. lowers
b. raises
c. does not change
d. none of the above

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NABCEP Certification Exam Prep
15. Answer: a Lowers

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NABCEP Certification Exam Prep
16. A 48 volt battery bank is used to provide power for critical
loads requiring 7458 Wh/day. Three days of autonomy are
required. What is the required capacity of the battery bank?

a. 155.4 Ah
b. 466 Ah
c. 604 Ah
d. None of the above

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NABCEP Certification Exam Prep
16. Answer: b. 466 Ah

7458 Wh ÷ 48V = 155.4 Ah/day

155.4 Ah/day x 3 days autonomy = 466 Ah

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NABCEP Certification Exam Prep
17. Critical loads operate for 12 hours. Three days of autonomy are
required and the preferred depth of discharge of 50%. What is the
average discharge rate?

a. C/180
b. C/72
c. C/36
d. C/24

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NABCEP Certification Exam Prep
17. Answer: b. C/72

12 hrs./day x 3 days autonomy = 36 hrs

36 hrs. ÷ 0.5 DOD = 72 hrs. ! C/72

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NABCEP Certification Exam Prep
18. A battery bank of 500 Ah is required. The depth of discharge is
50%, the minimum operating temperature is -10ºC and the average
discharge rate is C/128. According to the manufacturer’s specs. this
yields a temperature and discharge rate derating factor of
approximately 73%. What is the required battery bank capacity?

a. 250 Ah
b. 1370 Ah
c. 684 Ah
d. 1000 Ah

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NABCEP Certification Exam Prep
18. Answer: b. 1370Ah

Given 50% DOD, the battery bank must be:

500 Ah ÷ 0.5 = 1000 Ah

Because 27% of the capacity is lost due to cold temperatures per the
manufacturer:

1000 Ah ÷ 0.73 = 1369.9 Ah ! 1370Ah

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NABCEP Certification Exam Prep
19. A battery bank must supply 1200 Ah and will operate at 48V.
The battery selected is an 800 Ah battery. How many 6V batteries
will be required in this battery bank?

a. 8
b. 16
c. 24
d. None of the above

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NABCEP Certification Exam Prep
19. Answer: b. 16

48V bank ÷ 6V battery = 16 batteries in series to achieve voltage

1200 Ah ÷ 800Ah = 1.5 ! 2 parallel strings of batteries

8 x 2 = 16

Nothing was mentioned about DOD.

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NABCEP Certification Exam Prep
20. A PV system needs to supply 5834 Wh per day. The daily
average insolation is 4.8 peak sun hours. The battery system
charging efficiency is 0.9. The nominal voltage is 48V. What is the
required array current not including any additional deration
factors?

a. 27.9A
b. 28.1A
c. 64.8A
d. 25.3A

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NABCEP Certification Exam Prep
20. Answer: b. 28.1A

5834 Wh/day ÷ 4.8 Peak Sun Hours = 1215.4W

1215.4W ÷ 0.9 charging efficiency = 1350.5W

1350.5W ÷ 48V = 28.1A

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NABCEP Certification Exam Prep
21. You are an installer called to move a residential two-axis tracker
system from Yuma, AZ to Duluth, MN. Before reinstalling the
system what should you check?

a) The system open circuit voltage

b) The new house branch circuit amperage
c) The breaker size of the main panel
d) The insolation difference

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NABCEP Certification Exam Prep
21. Answer: a. Check the Voc.

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NABCEP Certification Exam Prep
22. For a PV array to directly face the sun at 11 AM solar time
on June 21st at 30⁰N latitude, at what tilt and azimuth angles
should the modules be mounted? Use the sun-path chart
provided.

47
Dr. Sean White teaches HeatSpring’s NABCEP Prep Course.
Study for your test with Sean: http://bit.ly/NABCEPprep

48
NABCEP Certification Exam Prep
22. Answer:

Approximately 14⁰ elevation and 63⁰E azimuth

Elevation = 90⁰ - 76⁰ = 14⁰

Note: The sum of all angles in any triangle = 180⁰

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NABCEP Certification Exam Prep
23. The purpose of a linear current booster is to:
a. Keep its output voltage the same as its input voltage and boost the
output current to a value larger than the input current.
b. Convert a high input voltage and low input current to a lower
output voltage and a higher output current.
c. Convert a low input voltage and high input current to a higher
input voltage and a lower input current.
d. Keep its output current the same as its input current and boost the
output voltage to a value larger than the input voltage.

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NABCEP Certification Exam Prep
23. Answer: b. Convert a high input voltage and low input current
to a lower output voltage and a higher output current

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NABCEP Certification Exam Prep
24. Where the removal of the utility-interactive inverter or other
equipment disconnects the bonding connection between the
grounding electrode conductor and the photovoltaic source and/or
the photovoltaic output circuit grounded conductor, a____ shall be
installed to maintain the system grounding while the inverter or
other equipment is removed.

a. Grounding-electrode conductor
b. Fuse
c. Bonding jumper
d. Overcurrent device

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NABCEP Certification Exam Prep
24. Answer:
c. Bonding jumper

NEC Article 690.49

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NABCEP Certification Exam Prep
25. In addition to NEC Article 690. where else in the NEC are over-
current devices are addressed?

a. Article 250
b. Article 300
c. Article 100
d. Article 240

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NABCEP Certification Exam Prep
25. Answer:
d. Article 240

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 NABCEP Certification Exam Prep
26. You are inspecting a PV system in Oregon. The array is facing south on a 6/12
pitch roof and the PV equipment is on the east side of the house 60 feet from the
combiner. You see an SMA inverter with a #6 GEC run to the ground rod. To the
right, is a 30A disconnect with EMT extending to the roof. Inside the disconnect
you see two black PV conductors landed onto the terminals. Your inspection of the
combiner box on the roof shows two black PV wires. Each one is terminated on a
fuse holder and the ground wire is terminated on the ground bus. What type of PV
system are you inspecting?

a. Positive ground system

b. Bi-polar
c. Ungrounded
d. Negative ground system

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 NABCEP Certification Exam Prep
26. Answer:

c. Ungrounded

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 NABCEP Certification Exam Prep
27. USE-2 wire must be strapped and secured between modules at
intervals no more than:

a. 6’
b. 3’
c. 4.5’
d. 10’

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NABCEP Certification Exam Prep
27. Answer:

c. 4.5’

Installation methods for exterior USE-2 conductors, commonly

used in PV arrays, are stated in NEC 338.10(B)(4). This section
refers to Article 334.30 for support methods. Article 334 is
entitled Non-Metallic Sheathed Cable (often referred to by the
trade name Romex).

The requirements for fastening NM cable are well understood by

AHJ. (Field Inspection Guidelines by Bill Brooks)

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 NABCEP Certification Exam Prep
28. If the uplift force on a system is 1,200 pounds with a safety
factor of 1.5, what is the uplift force with a safety factor of 2?

a. 800 lbs
b. 1200 lbs
c. 1400 lbs
d. 1600 lbs

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NABCEP Certification Exam Prep
28. Answer:

d. 1600 lbs

1200 lbs ÷ 1.5 = 800 lbs

800 lbs x 2 = 1600 lbs

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NABCEP Certification Exam Prep
29. When GFP is used on an inverter, the grounded and grounding
conductors should be:

a. Grounded: Isolated, grounding: Isolated from case

b. Grounding: Isolated, grounded: Connected to case
c. Both: Connected to case
d. Grounding: Connected to case, Grounded: Bonded to grounding

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NABCEP Certification Exam Prep
29. Answer:

d. Grounding: Connected to case, Grounded: Bonded to grounding

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 NABCEP Certification Exam Prep
30. A customer in New Mexico has a 6000W grid-tied PV system.
Every day around noon during the summer, the 25A solar breaker
trips. The inverter is on the south side of the house. The conduit run
from the inverter to the transition box is 200 ft. The array is facing
true south at latitude. What should be done to prevent the breaker
from tripping?

a. Move the inverter out of the sun to lower its internal temperature
b. Increase the breaker size
c. Increase the wire size between the transition box and the inverter
to compensate for voltage drop
d. Decrease the tilt of the array to lower production

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NABCEP Certification Exam Prep
30. Answer:

b. Increase the breaker size.

6000W ÷ 1.2 = 5000W inverter

5000W ÷ 240V = 20.8A
20.8A x 1.25 = 26.04A

A 30 amp breaker was needed for this system

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NABCEP Certification Exam Prep
31. You are on a roof in December to check system production
compared with the expected production. You know there will be
some shading around 3 p.m. In addition to a multi-meter, what tools
will you need?

a. Pathfinder and Temp. gauge

b. Pathfinder and Irradiance meter
c. Irradiance meter and temp. gauge
d. Temp. gauge and inclinometer

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NABCEP Certification Exam Prep
31. Answer:

c. Irradiance meter and temp. gauge

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NABCEP Certification Exam Prep
32. When checking short-circuit current on a string of modules, what
do you do first?

a. Measure short circuit current

b. Inspect for shading
c. Measure voltage
d. Measure operating current

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NABCEP Certification Exam Prep
32. Answer:

d. Measure operating current

You must verify that the circuit is in the open position before you
loosen any terminals to which the conductor is attached.

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 NABCEP Certification Exam Prep
33. When troubleshooting modules, what do you do?

a. Disconnect all loads to prevent module arcing when unplugged

b. Open DC disconnect on the inverter
c. Open AC disconnect
d. Pull fuses in combiner box

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NABCEP Certification Exam Prep
33. Answer:

a. Disconnect all loads to prevent module arcing when unplugged

All are correct: 1. Open the AC disconnects. 2. Open the DC

disconnects. 3. Pull fuses in the combiner box.

Taking all these steps ensures that all loads are disconnected. Then it
is safe to work on modules.

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 NABCEP Certification Exam Prep
34. If an inverter is being used in sell mode, the PV charge controller bulk and
float voltages and the inverter bulk and float voltages should be set as
follows:

a. Charge controller bulk and float should be higher than bulk and float of
inverter

b. Charge controller bulk and float should be lower the bulk and float of
inverter

c. Bulk should be higher than float on the inverter

d. Float should be higher than float on the inverter

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NABCEP Certification Exam Prep
34. Answer:

a. Charge controller bulk and float should be higher

than bulk and float of inverter

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NABCEP Certification Exam Prep
35. At 75⁰C which wire would be used?

a. THW-2, XHHW, RHH

b. THHN, THW, USE
c. THW, XHHW, THWN
d. USE-2, RHW-2, THW

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NABCEP Certification Exam Prep
35. Answer:

c. THW, XHHW, THWN

NEC 310.15(B)(16)

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NABCEP Certification Exam Prep
36. What should be done if USE-2 wires are found to resting
against a roof?

a. Lift them and strap at 3’ distances.

b. Lift them and strap them at 5’ distances.
c. Put them in EMT conduit.
d. Put them in liquid-tight conduit.

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NABCEP Certification Exam Prep
36. Answer:

a. Lift them and strap at 3’ distances

NEC 338.10(B) (4).

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NABCEP Certification Exam Prep
37. A potential customer wants a PV system. His average monthly
usage is 450kWh. He has a southeast facing roof that is 15 degrees
off true south with a 30 degree tilt. He receives 4.9 peak sun hours
on average per day. He has a 240V split-phase panel with a 200A
breaker. What is the maximum inverter output that can be
connected to his electrical panel?
a. 25A
b. 30A
c. 32A
d. 35A

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NABCEP Certification Exam Prep
37. Answer:

c. 32A

200A bus bar X 120% = 240A

(NEC 705.12(D)(2)

240A – 200A main breaker = 40A max solar breaker

40A ÷ 125% = 32A

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NABCEP Certification Exam Prep
38. You are installing a ground wire to the rebar on a pole mount.
What size rebar must be used?
a. #2
b. #4
c. #6
d. #8

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NABCEP Certification Exam Prep
38. Answer:
b. #4
NEC 250.52(A)(3)(1)

Rebar comes in 1/8 in. increments. Rebar is required to be no

smaller than ½ in.
1/8 = 0.125
0.5 ÷ 0.125 = 4

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NABCEP Certification Exam Prep
39. A 55 foot tree will grow 25 feet during the life of the PV system.
How far away does a ground mount system need to be? The system is
located at 40 degrees latitude, the sun’s lowest altitude angle is 14
degrees and the azimuth angle is 41 degrees.
a. 263’
b. 280’
c. 240’
d. 330’

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 NABCEP Certification Exam Prep
39. Answer:

d. 330’

55’ + 25’ (tree height at leading edge) = 320.8’

Tan(14⁰)

I did not multiply by the COS (41) because the question does not say
that the array is due north of the tree.

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 NABCEP Certification Exam Prep
40. A weather vane falls onto an array and there is broken glass. The system is
still working. What is the main safety concern and how do you handle it?

a. No concern. Open AC disconnect, remove vane, unplug broken modules

and replace them.
b. Little concern. Open AC disconnect, put on gloves for broken glass, remove
vane and unplug modules to be replaced.
c. Medium concern. Open DC disconnect, remove vane and unplug modules
to be replaced.
d. Vane has high potential. Open DC disconnect, unplug all modules and
remove vane with voltage rated gloves.

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NABCEP Certification Exam Prep
40. Answer:

d. Vane has high potential. Open DC disconnect, unplug all

modules and remove vane with voltage rated gloves.

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 NABCEP Certification Exam Prep
41. What is the most important consideration for construction of a
ground mount array in a heavy snow area?
a. Tilt angle
b. Distance from ground to bottom of array
c. Row-to-row shading
d. All of the above

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 NABCEP Certification Exam Prep
41. Answer:
b. Distance from ground to bottom of array

Incorrect answers:
a, Tilt angle. Typically on a ground-mount the array will be at latitude.
Even at latitude -15⁰ in areas where there is lots of snow this angle will
allow snow shedding.
b. Row-to-row shading. The question did not mention multiple rows.
c. Could be correct but not the most accurate choice.

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NABCEP Certification Exam Prep
42. System drawings call for #10 wire. The system calls for a 50 amp
breaker. What size should the wire be?
a. #10
b. #8
c. #12
d. #6

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 NABCEP Certification Exam Prep
42. Answer:

b. #8

NEC 240.4(D) (7) Copper #10 limited to a 30A overcurrent device.

NEC Table 310.15(B)(16) in either 75 or 90 degree column shows #8

good for a 50A breaker

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 NABCEP Certification Exam Prep
43. At what depth should a 1/0 ground wire be buried?
a. 12”
b. 18”
c. 30”
d. It shouldn’t be buried

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NABCEP Certification Exam Prep
43. Answer:
c. 30”

A 1/0 ground wire is actually a ground ring, per Article 250.52 (A) (4)
Article 250.53 (F) states that a 30” minimum burial depth for a
ground ring is required.

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NABCEP Certification Exam Prep
44. An inverter is on the north side of a house and the array is on the
south. Where should the DC and AC disconnects be?
a. The DC disconnect should be close to the array and the AC disconnect
should be next to the inverter.

b. Both the DC and AC disconnects should be close to the main service.

c. The AC disconnect should be close to the array and the DC next to the
inverter.

d. The DC and AC disconnects should be on either side of the inverter.

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 NABCEP Certification Exam Prep
44. Answer:
d. The DC and AC disconnects should be on either side of the inverter.

NEC 690.17
Incorrect answers:
a. and c. Neither of these satisfy the “readily accessible” requirement.
b. Since we don’t know from the question that the main service is in an
accessible location, stipulating that the disconnects go close to the
main service does not by itself satisfy 690.17.

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 NABCEP Certification Exam Prep
45. At what distance from the junction box must USE-2 wire be
secured?
a. 10”
b. 12”
c. 18”
d. 36”

40
NABCEP Certification Exam Prep
45. Answer:
b. 12”

NEC 334.30

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 NABCEP Certification Exam Prep
46. The power loss due to temperature for a silicon module is listed as -0.5%/
⁰C in the manufacturer’s specifications. The manufacturer recommends
two array mounting options; one with a ¾” air gap between the module
and the roof and one with a 3” air gap. The closer mounting system
causes the array to operate 10⁰C hotter on average throughout the year.
Which mounting system will produce the most energy? How much?

a. ¾” gap by 5%
b. 3” gap by 5%
c. 3” gap by 10%
d. Both will produce the same

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 NABCEP Certification Exam Prep
46. Answer: b. 3” gap by 5%

NEC Section: Technically none, but Table 310.15(B)(3)(c) serves as a guide.

Solution:

It should be intuitive based on the Table that a 3” gap will be cooler than a ¾”
gap. So answers “a” and “d” can be eliminated. Since the temperature change
is 10⁰C, the larger gap will produce 5% more power:

0.5%/⁰C x 10⁰C = 5%

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 NABCEP Certification Exam Prep
47. A 7kW PV system using 3 utility interactive inverters listed to UL 1741 is planned for the roof of a duplex. The inverters may
be installed on the roof near the PV array if which of the following conditions are met?

a. All inverters are mounted in a readily accessible location. DC disconnects are at the inverters. AC disconnects are at the
point of interconnection with the service equipment. An array wiring plaque is installed at the inverter location.

b. Although the inverters are not mounted in a readily accessible location, there is an additional readily accessible AC
disconnect for the system. AC and DC disconnects for all 3 inverters are mounted in or near the inverters. A power
rating plaque is mounted on each inverter.

c. All inverters are mounted where they can be serviced from a service platform. AC and DC disconnects for all 3 inverters are
mounted in or near the inverters. There is an additional readily accessible AC disconnect for the system. A power rating
plaque is mounted on each inverter.

d. Although none of the inverters are mounted in a readily accessible location, there is an additional readily accessible AC
disconnect for the system at the service entrance equipment. AC and DC disconnects for each inverter are mounted in
or near the inverters. Plaques with a system description showing all power sources are mounted at the inverters and the
service equipment.

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 NABCEP Certification Exam Prep
47. Answer: d. Although none of the inverters are mounted in a readily accessible location,
there is an additional readily accessible AC disconnect for the system at the service
entrance equipment. AC and DC disconnects for each inverter are mounted in or near the
inverters. Plaques with a system description showing all power sources are mounted at the
inverters and the service equipment.

Solution
NEC 2011 Article 690.14 (D) (1-4) Utility-interactive inverters mounted in not-readily –
accessible-locations.
NEC 2011 Article 690.14 (C)(1) Requirements and location for Disconnecting Means
NEC 2011 Article 705.10 Permanent plaque or directory.

a. Does not meet 690.14 D 2, 4.

b. Meets 690.14 D 1- 2, does not meet 4.
c. Meets 690.14 D 1-2, does not meet 4.
d. Meets all definitions provided by 690.14(D)(1-4) and 705.70

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 NABCEP Certification Exam Prep
Use the following system specifications to answer questions 23 and
24.

PV array size: 9kW

Modules: 200W, 39 lbs each
Location: flat roof of a two-story commercial structure
Mounting: 9’ x 5’, 43 lb aluminum frames holding 3 modules each
Total weight required: 925 lbs per mounting frame
Ballast: 8’”x8”x16” concrete blocks, 27 lbs each

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NABCEP Certification Exam Prep
48. What is the total number of concrete blocks required to ballast
the system?

a. 765
b. 29
c. 435
d. 514

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 NABCEP Certification Exam Prep
48. Answer: c. 435

Solution
Number of modules:
9000 (System Watts) ÷ 200 (Watts/module) = 45 modules
45 modules ÷ 3 modules/frame = 15 frames for the system
43 lbs./frame + (3 x 39 lbs./module) = 160 lbs. (frame & modules)
925 lbs. (required weight per frame) – 160 lbs. = 765 lbs. of ballast
765 lbs. ÷ 27 lbs. (block weight) = 28.3 ! 29 blocks per frame
15 (frames required) x 29 (blocks) = 435 blocks to ballast the system

Note: The early answer “b. 29” is included to catch test takers who are rushing or not fully understanding what has
actually been asked.

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 NABCEP Certification Exam Prep
49. What is the approximate dead load within the system footprint
that the roof must withstand?

a. 7 lbs./sq. ft.
b. 21 lbs./sq. ft.
c. 42 lbs./sq. ft.
d. 63 lbs./sq. ft.

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NABCEP Certification Exam Prep

49. Answer: b. 21 lbs./sq. ft.

925 lbs. ÷ (9 ft. x 5 ft.) = 20.56 lbs./sq. ft.

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 NABCEP Certification Exam Prep
50. A utility interactive PV system is installed on a commercial building. The array is roof
mounted and operates at 372Vmp with an operating current of 8.56A. When inspecting
the source circuit combiner box located next to the array, you observe the following: the
ungrounded PV source circuit conductor is black USE-2/RHW-2, the frame grounding
conductor is #6 solid Cu, the box is a NEMA4 rated metal box, the PV output conductors
leave the (+) and (–) terminal busses and pass into a male EMT adapter secured with a
locknut. What is required to bring the combiner box into compliance with the NEC?

a. A 600VDC 15A fuse with touch-safe fuse holder must be installed

on the ungrounded source circuit conductor.
b. A grounding bushing must be installed on the EMT adapter.
c. The frame grounding conductor must be changed to #8 stranded Cu.
d. None of the above.

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 NABCEP Certification Exam Prep
50. Answer: d. None of the above

Solution
250.97 states that, for circuits of over 250V to ground, the electrical continuity
of metal raceways … shall be ensured by one or more of the methods
specified for services in 250.92(B)
250.92(B)(1-4)

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 NABCEP Certification Exam Prep
50. Notes Part 1:
a. Could be correct, but the presence or lack thereof of an OCPD was not
specifically mentioned and the language reads the ungrounded not one of
the ungrounded, etc.

Plus, not all single string circuits need OCP to satisfy Code- see J Wiles To
Fuse or Not to Fuse.

b. To provide a reliable bonding connection, a bonding bushing would be

required only if the box had concentric knockouts which are not
encountered in NEMA4 boxes unless listed.

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 NABCEP Certification Exam Prep
50. Notes Part 2:

c. This choice is a trap. There are instances where the frame ground would
need to be increased from #8 to #6, i.e. if it was subject to physical damage.
This is meant as a trick for people who think they are positive about the
Code but don’t bother checking.

This question is important because this issue is seen quite regularly from both
novice PV installers and licensed electricians unfamiliar with the Code.

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