NABCEP PV Associate Exam - Questions With Correct
Solutions
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 monthly energy use? Right
Ans - 68KWh
1HP = 746W
746W * 0.1 * 24hours * 30days = 53712Wh
20W * 24hrs * 30days = 14400Wh
14400 + 53712 = 68112Wh
68kWh
What kind of ground faults do most inverters detect? Right Ans - DC
Inverters detect dc ground faults. AC ground faults are detected on the AC side
of the inverter at the distribution paned (MSP, load center). Most inverters are
not connected to high or medium voltage. Medium voltage is thousands of
volts, large utility scale inverters are connected to medium voltage via a
transformer
Current carrying ability of a conductor (wire) is called Right Ans -
Ampacity
According to ohms law and voltage drop, the relationship between voltage
drop and current is Right Ans - Proportional. Ohms law: V = I*R
More current makes more voltage drop. This is a reason why we need a larger
wire with more current, so the wire resistance is less with a larger wire and
there will be less voltage drop.
An array in a hot and dry place is not producing as expected in summer time.
Which of the following is NOT a likely problem:
a) Decreased ac wire size and voltage loss
b) String size too short
C) String size too long
D) Soiling Right Ans - C) String size too short. When it is hot, voltage can be
low. Too long of a string would be a problem when it is too cold not too hot.
When using a digital multimeter, what is the first thing you should do?
Right Ans - Inspect the meter. Always inspect first, look before you touch
, is the worst design error?
A) BIPV on a commercial job
B) A fast-growing tree to the north of an array in Idaho
C) PV at 5-degree tilt at 40 degrees latitude
D) Different tilt angles in a PV source circuit Right Ans - D) Different tilt or
azimuth operation within a source circuit is bad. Series connections should
not have different orientations
MPPT is for Right Ans - MPPT is maximum power point tracking and will
optimize the energy harnessed from PV. Some inverters have multiple MPPTs.
Charge controllers often, but don't always, have MPPTs
Concentrated PV:
A) Only works with direct sunlight
B) Usually has a single axis tracker
C) Will get 30% power during cloudy conditions
D) Is using heat to make electricity Right Ans - A) Only works in direct
sunlight. usually works with 2-axis trackers to always point at the sun and will
not work at all in cloudy conditions. Concentrated PV =! Concentrating Solar
thermal
Fall protection should be used at heights over Right Ans - 6 feet
Parallel PV circuit connections increase Right Ans - Parallel increase
current. Series increase voltage
Optimal tilt for off-grid PV system in the winter Right Ans - Latitude + 15
degrees is Optimal tilt to maximize winter production. The sun is lower in the
winter, requiring a higher tilt angle
What is the most acceptable rating of an enclosure for exposed circuit
conductors mounted on an outside wall? Right Ans - NEMA 3R
Bypass diodes are located in the
A) Combiner box
B) Inverter
C) Wiring harness
Solutions
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 monthly energy use? Right
Ans - 68KWh
1HP = 746W
746W * 0.1 * 24hours * 30days = 53712Wh
20W * 24hrs * 30days = 14400Wh
14400 + 53712 = 68112Wh
68kWh
What kind of ground faults do most inverters detect? Right Ans - DC
Inverters detect dc ground faults. AC ground faults are detected on the AC side
of the inverter at the distribution paned (MSP, load center). Most inverters are
not connected to high or medium voltage. Medium voltage is thousands of
volts, large utility scale inverters are connected to medium voltage via a
transformer
Current carrying ability of a conductor (wire) is called Right Ans -
Ampacity
According to ohms law and voltage drop, the relationship between voltage
drop and current is Right Ans - Proportional. Ohms law: V = I*R
More current makes more voltage drop. This is a reason why we need a larger
wire with more current, so the wire resistance is less with a larger wire and
there will be less voltage drop.
An array in a hot and dry place is not producing as expected in summer time.
Which of the following is NOT a likely problem:
a) Decreased ac wire size and voltage loss
b) String size too short
C) String size too long
D) Soiling Right Ans - C) String size too short. When it is hot, voltage can be
low. Too long of a string would be a problem when it is too cold not too hot.
When using a digital multimeter, what is the first thing you should do?
Right Ans - Inspect the meter. Always inspect first, look before you touch
, is the worst design error?
A) BIPV on a commercial job
B) A fast-growing tree to the north of an array in Idaho
C) PV at 5-degree tilt at 40 degrees latitude
D) Different tilt angles in a PV source circuit Right Ans - D) Different tilt or
azimuth operation within a source circuit is bad. Series connections should
not have different orientations
MPPT is for Right Ans - MPPT is maximum power point tracking and will
optimize the energy harnessed from PV. Some inverters have multiple MPPTs.
Charge controllers often, but don't always, have MPPTs
Concentrated PV:
A) Only works with direct sunlight
B) Usually has a single axis tracker
C) Will get 30% power during cloudy conditions
D) Is using heat to make electricity Right Ans - A) Only works in direct
sunlight. usually works with 2-axis trackers to always point at the sun and will
not work at all in cloudy conditions. Concentrated PV =! Concentrating Solar
thermal
Fall protection should be used at heights over Right Ans - 6 feet
Parallel PV circuit connections increase Right Ans - Parallel increase
current. Series increase voltage
Optimal tilt for off-grid PV system in the winter Right Ans - Latitude + 15
degrees is Optimal tilt to maximize winter production. The sun is lower in the
winter, requiring a higher tilt angle
What is the most acceptable rating of an enclosure for exposed circuit
conductors mounted on an outside wall? Right Ans - NEMA 3R
Bypass diodes are located in the
A) Combiner box
B) Inverter
C) Wiring harness
