CO Steam & Hot Water Heating
Contractor Exam Practice Questions
And Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf.
1. Which component in a hydronic heating system is primarily
responsible for removing entrained air from the circulating water
before it can cause noise, corrosion, or circulation problems?
A. Pressure-reducing valve
B. Air separator
C. Backflow preventer
D. Check valve
B. Air separator
An air separator is designed to remove entrained and dissolved air from
hydronic water. Removing air helps prevent corrosion, noise, poor heat
transfer, and air binding of circulators or terminal units.
2. In a closed hot-water heating system, what is the primary purpose
of an expansion tank?
A. To increase boiler firing rate
B. To provide additional combustion air
,C. To accommodate the expansion and contraction of system water
D. To prevent all system pressure changes
C. To accommodate the expansion and contraction of system water
Water expands as its temperature increases. The expansion tank
provides a compressible volume that absorbs this change and helps
maintain acceptable system pressure.
3. A hydronic boiler system has a normal operating pressure of
approximately 12 psi when cold. What is the principal function of
the boiler's pressure-relief valve?
A. Maintain minimum flow through the boiler
B. Prevent excessive system pressure from damaging equipment
C. Reduce incoming water pressure continuously
D. Remove dissolved oxygen from the water
B. Prevent excessive system pressure from damaging equipment
The pressure-relief valve is a safety device that opens when pressure
reaches its rated setpoint, protecting the boiler and piping from
dangerous overpressure.
4. Why is a low-water cutoff particularly important on a steam boiler?
A. It increases steam pressure during peak demand
B. It prevents the burner from operating when the boiler water level is
dangerously low
C. It automatically removes scale from the boiler
D. It controls the building's room temperature
,B. It prevents the burner from operating when the boiler water level is
dangerously low
A steam boiler must maintain adequate water coverage over heated
surfaces. A low-water condition can expose heat-transfer surfaces,
causing overheating, damage, or potentially dangerous boiler failure.
5. In a one-pipe steam heating system, what is the principal function
of a steam radiator air vent?
A. Admit air during heating and allow air to escape while steam enters
B. Increase boiler pressure
C. Supply make-up water to the radiator
D. Return condensate directly to the water main
A. Admit air during heating and allow air to escape while steam enters
The air vent allows air to leave the radiator as steam approaches and
closes when steam reaches it. Proper venting permits steam to distribute
through the system without trapping air.
6. What is the primary purpose of a condensate return system in a
steam heating installation?
A. Convert steam into combustion air
B. Return condensed steam to the boiler or condensate receiver
C. Increase the temperature of incoming fuel
D. Eliminate the need for boiler-water treatment
B. Return condensed steam to the boiler or condensate receiver
, Steam releases heat as it condenses. The resulting condensate can be
collected and returned to the boiler, conserving treated water and
reducing the energy required to heat replacement water.
7. Which condition most commonly causes water hammer in a steam
heating system?
A. Properly pitched condensate piping
B. Condensate accumulating in steam piping and being propelled by
moving steam
C. Correctly sized air vents
D. Excessive insulation on return piping
B. Condensate accumulating in steam piping and being propelled by
moving steam
Water hammer occurs when moving steam encounters pooled
condensate and accelerates the water into fittings, valves, or pipe ends.
Proper pipe pitch, drainage, and steam velocity control help prevent it.
8. In a steam distribution system, why must horizontal steam piping
generally be installed with appropriate pitch?
A. To allow condensate to drain toward designated collection points
B. To increase combustion efficiency
C. To prevent the boiler from producing steam
D. To increase the static water pressure in the system
A. To allow condensate to drain toward designated collection points
Contractor Exam Practice Questions
And Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A|
Instant Download Pdf.
1. Which component in a hydronic heating system is primarily
responsible for removing entrained air from the circulating water
before it can cause noise, corrosion, or circulation problems?
A. Pressure-reducing valve
B. Air separator
C. Backflow preventer
D. Check valve
B. Air separator
An air separator is designed to remove entrained and dissolved air from
hydronic water. Removing air helps prevent corrosion, noise, poor heat
transfer, and air binding of circulators or terminal units.
2. In a closed hot-water heating system, what is the primary purpose
of an expansion tank?
A. To increase boiler firing rate
B. To provide additional combustion air
,C. To accommodate the expansion and contraction of system water
D. To prevent all system pressure changes
C. To accommodate the expansion and contraction of system water
Water expands as its temperature increases. The expansion tank
provides a compressible volume that absorbs this change and helps
maintain acceptable system pressure.
3. A hydronic boiler system has a normal operating pressure of
approximately 12 psi when cold. What is the principal function of
the boiler's pressure-relief valve?
A. Maintain minimum flow through the boiler
B. Prevent excessive system pressure from damaging equipment
C. Reduce incoming water pressure continuously
D. Remove dissolved oxygen from the water
B. Prevent excessive system pressure from damaging equipment
The pressure-relief valve is a safety device that opens when pressure
reaches its rated setpoint, protecting the boiler and piping from
dangerous overpressure.
4. Why is a low-water cutoff particularly important on a steam boiler?
A. It increases steam pressure during peak demand
B. It prevents the burner from operating when the boiler water level is
dangerously low
C. It automatically removes scale from the boiler
D. It controls the building's room temperature
,B. It prevents the burner from operating when the boiler water level is
dangerously low
A steam boiler must maintain adequate water coverage over heated
surfaces. A low-water condition can expose heat-transfer surfaces,
causing overheating, damage, or potentially dangerous boiler failure.
5. In a one-pipe steam heating system, what is the principal function
of a steam radiator air vent?
A. Admit air during heating and allow air to escape while steam enters
B. Increase boiler pressure
C. Supply make-up water to the radiator
D. Return condensate directly to the water main
A. Admit air during heating and allow air to escape while steam enters
The air vent allows air to leave the radiator as steam approaches and
closes when steam reaches it. Proper venting permits steam to distribute
through the system without trapping air.
6. What is the primary purpose of a condensate return system in a
steam heating installation?
A. Convert steam into combustion air
B. Return condensed steam to the boiler or condensate receiver
C. Increase the temperature of incoming fuel
D. Eliminate the need for boiler-water treatment
B. Return condensed steam to the boiler or condensate receiver
, Steam releases heat as it condenses. The resulting condensate can be
collected and returned to the boiler, conserving treated water and
reducing the energy required to heat replacement water.
7. Which condition most commonly causes water hammer in a steam
heating system?
A. Properly pitched condensate piping
B. Condensate accumulating in steam piping and being propelled by
moving steam
C. Correctly sized air vents
D. Excessive insulation on return piping
B. Condensate accumulating in steam piping and being propelled by
moving steam
Water hammer occurs when moving steam encounters pooled
condensate and accelerates the water into fittings, valves, or pipe ends.
Proper pipe pitch, drainage, and steam velocity control help prevent it.
8. In a steam distribution system, why must horizontal steam piping
generally be installed with appropriate pitch?
A. To allow condensate to drain toward designated collection points
B. To increase combustion efficiency
C. To prevent the boiler from producing steam
D. To increase the static water pressure in the system
A. To allow condensate to drain toward designated collection points
