NGWA Vertical Closed Loop Drilling
Certification Exam Practice Questions
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
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1. What is the primary purpose of a vertical closed loop geothermal
system?
A) Provide natural gas
B) Transfer heat to or from the ground
C) Pump water to the surface
D) Store electricity
Rationale: Closed loop systems circulate a fluid to exchange heat
with the ground for heating or cooling.
,2. Which material is most commonly used for vertical loop piping in
geothermal systems?
A) Steel
B) Copper
C) High-density polyethylene (HDPE)
D) PVC
Rationale: HDPE is preferred due to its flexibility, corrosion
resistance, and durability underground.
3. How deep do most vertical closed loop boreholes typically extend?
A) 50–100 feet
B) 100–200 feet
C) 150–500 feet
D) 500–1000 feet
Rationale: Depth depends on system load and ground thermal
properties; most range from 150–500 feet.
4. What is the standard spacing between boreholes in a vertical closed
loop field?
A) 10–15 feet
B) 15–20 feet
C) 25–30 feet
D) 30–40 feet
, Rationale: Proper spacing prevents thermal interference between
boreholes.
5. Which fluid is commonly used in vertical closed loop systems?
A) Mineral oil
B) Water with antifreeze
C) Gasoline
D) Saltwater
Rationale: A water/antifreeze mixture prevents freezing while
transferring heat efficiently.
6. What is the main advantage of vertical loops over horizontal loops?
A) Lower installation cost
B) Smaller land footprint
C) Easier excavation
D) Requires less drilling expertise
Rationale: Vertical loops are installed deep, requiring less surface
area than horizontal loops.
7. What type of drilling method is most commonly used for vertical
closed loop boreholes?
A) Auger drilling
, B) Rotary drilling
C) Cable tool drilling
D) Percussion drilling
Rationale: Rotary drilling allows deep, straight boreholes suitable for
vertical loops.
8. When designing a vertical closed loop, which factor is most critical for
heat transfer?
A) Pipe color
B) Soil pH
C) Ground thermal conductivity
D) Atmospheric humidity
Rationale: Ground thermal conductivity directly affects system
efficiency.
9. What is the recommended diameter of vertical closed loop boreholes
for residential systems?
A) 1–2 inches
B) 2–3 inches
C) 4–6 inches
D) 8–10 inches
Rationale: Borehole diameter is sized to accommodate the pipe and
grout while ensuring proper heat transfer.
Certification Exam Practice Questions
And Correct Answers (Verified Answers)
Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of a vertical closed loop geothermal
system?
A) Provide natural gas
B) Transfer heat to or from the ground
C) Pump water to the surface
D) Store electricity
Rationale: Closed loop systems circulate a fluid to exchange heat
with the ground for heating or cooling.
,2. Which material is most commonly used for vertical loop piping in
geothermal systems?
A) Steel
B) Copper
C) High-density polyethylene (HDPE)
D) PVC
Rationale: HDPE is preferred due to its flexibility, corrosion
resistance, and durability underground.
3. How deep do most vertical closed loop boreholes typically extend?
A) 50–100 feet
B) 100–200 feet
C) 150–500 feet
D) 500–1000 feet
Rationale: Depth depends on system load and ground thermal
properties; most range from 150–500 feet.
4. What is the standard spacing between boreholes in a vertical closed
loop field?
A) 10–15 feet
B) 15–20 feet
C) 25–30 feet
D) 30–40 feet
, Rationale: Proper spacing prevents thermal interference between
boreholes.
5. Which fluid is commonly used in vertical closed loop systems?
A) Mineral oil
B) Water with antifreeze
C) Gasoline
D) Saltwater
Rationale: A water/antifreeze mixture prevents freezing while
transferring heat efficiently.
6. What is the main advantage of vertical loops over horizontal loops?
A) Lower installation cost
B) Smaller land footprint
C) Easier excavation
D) Requires less drilling expertise
Rationale: Vertical loops are installed deep, requiring less surface
area than horizontal loops.
7. What type of drilling method is most commonly used for vertical
closed loop boreholes?
A) Auger drilling
, B) Rotary drilling
C) Cable tool drilling
D) Percussion drilling
Rationale: Rotary drilling allows deep, straight boreholes suitable for
vertical loops.
8. When designing a vertical closed loop, which factor is most critical for
heat transfer?
A) Pipe color
B) Soil pH
C) Ground thermal conductivity
D) Atmospheric humidity
Rationale: Ground thermal conductivity directly affects system
efficiency.
9. What is the recommended diameter of vertical closed loop boreholes
for residential systems?
A) 1–2 inches
B) 2–3 inches
C) 4–6 inches
D) 8–10 inches
Rationale: Borehole diameter is sized to accommodate the pipe and
grout while ensuring proper heat transfer.
