Arizona AZ C-74 Boilers,
Steamfitting & Process Piping,
Including Solar Contractor
Practice Exam | Questions,
Verified Answers & Detailed
Rationales | Complete
Contractor License Exam Prep
Study Guide | Updated 2026
Boilers
1. What is the primary purpose of a boiler safety relief
valve?
A. Increase boiler pressure
B. Control fuel consumption
C. Prevent excessive pressure from damaging the boiler
D. Increase water temperature
Correct answer: Prevent excessive pressure from
damaging the boiler
Rationale: A safety relief valve automatically releases
pressure when pressure reaches its set point,
protecting the boiler and connected system from
dangerous overpressure.
2. What condition is most likely to cause scale buildup
on boiler heat-transfer surfaces?
A. Properly treated feedwater
B. High concentrations of dissolved minerals
,C. Excessive insulation
D. Low combustion temperature
Correct answer: High concentrations of dissolved
minerals
Rationale: Minerals such as calcium and magnesium can
precipitate on heated surfaces and form scale, reducing
heat transfer and potentially causing overheating.
3. What is the primary function of boiler blowdown?
A. Increase steam pressure
B. Remove concentrated impurities from boiler water
C. Increase burner efficiency
D. Add oxygen to the boiler
Correct answer: Remove concentrated impurities from
boiler water
Rationale: Blowdown removes dissolved and suspended
solids that become concentrated as water is converted
to steam.
4. What happens to water when it is converted into
saturated steam at a constant pressure?
A. Its temperature necessarily falls
B. It absorbs latent heat
C. Its density increases substantially
D. It loses all internal energy
Correct answer: It absorbs latent heat
Rationale: During the phase change from saturated
liquid to saturated vapor, heat is absorbed as latent
heat while the pressure and saturation temperature
remain essentially constant.
,5. What is the purpose of a low-water cutoff on a boiler?
A. Increase water circulation
B. Shut down the burner when the water level becomes
dangerously low
C. Increase steam pressure
D. Reduce chimney draft
Correct answer: Shut down the burner when the water
level becomes dangerously low
Rationale: A low-water cutoff protects the boiler from
firing without adequate water coverage, which can
result in severe overheating and equipment failure.
6. Why is maintaining proper boiler water level
important?
A. It eliminates the need for a relief valve
B. It protects heat-transfer surfaces from overheating
C. It increases fuel pressure
D. It prevents all corrosion
Correct answer: It protects heat-transfer surfaces from
overheating
Rationale: Adequate water coverage allows heat to be
transferred safely from the furnace and heating
surfaces into the water.
7. What is the purpose of an expansion tank in a closed
hot-water heating system?
A. Store fuel
B. Absorb thermal expansion of the water
C. Increase burner capacity
D. Remove sediment from the boiler
Correct answer: Absorb thermal expansion of the water
, Rationale: Heated water expands. The expansion tank
provides a compressible space that accommodates the
volume increase and helps control system pressure.
8. What is a common result of excessive boiler pressure?
A. Improved safety
B. Reduced water temperature
C. Activation of pressure safety devices
D. Elimination of steam formation
Correct answer: Activation of pressure safety devices
Rationale: When pressure rises to an unsafe level,
properly selected and maintained safety devices
operate to prevent further pressure increase.
9. What is the purpose of refractory material in a boiler
furnace?
A. Conduct electricity
B. Protect furnace components from high temperatures
C. Increase water hardness
D. Lubricate boiler tubes
Correct answer: Protect furnace components from high
temperatures
Rationale: Refractory materials withstand high
temperatures and protect furnace surfaces while
helping contain and direct combustion heat.
10. What is the primary purpose of a boiler water-gauge
glass?
A. Measure fuel pressure
B. Indicate boiler water level
C. Measure stack temperature
D. Measure steam velocity
Steamfitting & Process Piping,
Including Solar Contractor
Practice Exam | Questions,
Verified Answers & Detailed
Rationales | Complete
Contractor License Exam Prep
Study Guide | Updated 2026
Boilers
1. What is the primary purpose of a boiler safety relief
valve?
A. Increase boiler pressure
B. Control fuel consumption
C. Prevent excessive pressure from damaging the boiler
D. Increase water temperature
Correct answer: Prevent excessive pressure from
damaging the boiler
Rationale: A safety relief valve automatically releases
pressure when pressure reaches its set point,
protecting the boiler and connected system from
dangerous overpressure.
2. What condition is most likely to cause scale buildup
on boiler heat-transfer surfaces?
A. Properly treated feedwater
B. High concentrations of dissolved minerals
,C. Excessive insulation
D. Low combustion temperature
Correct answer: High concentrations of dissolved
minerals
Rationale: Minerals such as calcium and magnesium can
precipitate on heated surfaces and form scale, reducing
heat transfer and potentially causing overheating.
3. What is the primary function of boiler blowdown?
A. Increase steam pressure
B. Remove concentrated impurities from boiler water
C. Increase burner efficiency
D. Add oxygen to the boiler
Correct answer: Remove concentrated impurities from
boiler water
Rationale: Blowdown removes dissolved and suspended
solids that become concentrated as water is converted
to steam.
4. What happens to water when it is converted into
saturated steam at a constant pressure?
A. Its temperature necessarily falls
B. It absorbs latent heat
C. Its density increases substantially
D. It loses all internal energy
Correct answer: It absorbs latent heat
Rationale: During the phase change from saturated
liquid to saturated vapor, heat is absorbed as latent
heat while the pressure and saturation temperature
remain essentially constant.
,5. What is the purpose of a low-water cutoff on a boiler?
A. Increase water circulation
B. Shut down the burner when the water level becomes
dangerously low
C. Increase steam pressure
D. Reduce chimney draft
Correct answer: Shut down the burner when the water
level becomes dangerously low
Rationale: A low-water cutoff protects the boiler from
firing without adequate water coverage, which can
result in severe overheating and equipment failure.
6. Why is maintaining proper boiler water level
important?
A. It eliminates the need for a relief valve
B. It protects heat-transfer surfaces from overheating
C. It increases fuel pressure
D. It prevents all corrosion
Correct answer: It protects heat-transfer surfaces from
overheating
Rationale: Adequate water coverage allows heat to be
transferred safely from the furnace and heating
surfaces into the water.
7. What is the purpose of an expansion tank in a closed
hot-water heating system?
A. Store fuel
B. Absorb thermal expansion of the water
C. Increase burner capacity
D. Remove sediment from the boiler
Correct answer: Absorb thermal expansion of the water
, Rationale: Heated water expands. The expansion tank
provides a compressible space that accommodates the
volume increase and helps control system pressure.
8. What is a common result of excessive boiler pressure?
A. Improved safety
B. Reduced water temperature
C. Activation of pressure safety devices
D. Elimination of steam formation
Correct answer: Activation of pressure safety devices
Rationale: When pressure rises to an unsafe level,
properly selected and maintained safety devices
operate to prevent further pressure increase.
9. What is the purpose of refractory material in a boiler
furnace?
A. Conduct electricity
B. Protect furnace components from high temperatures
C. Increase water hardness
D. Lubricate boiler tubes
Correct answer: Protect furnace components from high
temperatures
Rationale: Refractory materials withstand high
temperatures and protect furnace surfaces while
helping contain and direct combustion heat.
10. What is the primary purpose of a boiler water-gauge
glass?
A. Measure fuel pressure
B. Indicate boiler water level
C. Measure stack temperature
D. Measure steam velocity
