NYC Custodian Engineer Practice Exam
Questions and Answers with Rationales
Latest Versions
Question 1
A steam boiler's water level is significantly below the normal operating level. What
should the custodian engineer do FIRST?
A. Immediately add cold water to the hot boiler
B. Increase the burner firing rate
C. Determine why the water level is low and follow the boiler's safe
shutdown/water-level procedure
D. Open the steam outlet valve fully
Correct Answer: C
Rationale:
A dangerously low boiler water level can expose heating surfaces and cause severe
damage or a boiler failure. The engineer should not immediately introduce cold
water into an overheated boiler, because rapid temperature changes can cause
thermal shock. The cause of the low-water condition should be investigated and the
manufacturer's/emergency operating procedure followed.
Question 2
What is the primary purpose of a boiler low-water cutoff?
A. To increase steam pressure
B. To prevent the burner from operating when the boiler water level is dangerously
low
C. To increase combustion efficiency
D. To regulate building temperature
Correct Answer: B
,Rationale:
A low-water cutoff (LWCO) is a critical boiler safety device. It shuts down the
burner when the water level falls below a safe limit, helping prevent overheating
and potentially catastrophic boiler damage.
Question 3
A centrifugal pump is running, but little or no water is being delivered. Which
condition should be checked FIRST?
A. Paint condition on the motor
B. Whether the pump is properly primed and whether the suction supply is
available
C. Room lighting
D. Thermostat calibration
Correct Answer: B
Rationale:
A centrifugal pump generally requires an adequate liquid supply and, depending on
the installation, proper priming. A closed suction valve, blocked strainer,
inadequate water supply, or loss of prime can result in little or no flow.
Question 4
What is the primary function of a pressure relief valve on a boiler?
A. Increase operating pressure
B. Remove sediment from the boiler
C. Automatically relieve excessive pressure
D. Control combustion air
Correct Answer: C
Rationale:
The pressure relief valve is a safety device designed to open when pressure
,reaches its set point, preventing pressure from exceeding the safe design limits of
the equipment.
Question 5
A boiler flame repeatedly goes out shortly after ignition. Which is the BEST initial
approach?
A. Disable the flame safeguard
B. Increase the fuel pressure without testing
C. Investigate fuel supply, ignition, combustion air, and flame-sensing/safety
controls
D. Permanently bypass the safety control
Correct Answer: C
Rationale:
Repeated flame failure can result from inadequate fuel, ignition problems,
insufficient combustion air, dirty burners, flame-sensing problems, or control
faults. Safety controls should never be bypassed merely to keep equipment
operating.
Question 6
What is the purpose of a steam trap?
A. To increase steam pressure
B. To remove condensate and non-condensable gases while retaining steam as
designed
C. To introduce cold water into the boiler
D. To increase burner output
Correct Answer: B
Rationale:
Steam traps automatically discharge condensate and, depending on trap design, air
, and other non-condensables from steam systems while minimizing the loss of live
steam.
Question 7
A water gauge glass on a steam boiler provides the engineer with information
about:
A. Fuel pressure
B. Boiler water level
C. Steam temperature only
D. Combustion-air pressure
Correct Answer: B
Rationale:
The gauge glass provides a direct visual indication of the boiler's water level.
Maintaining the correct water level is essential for safe boiler operation.
Question 8
What is cavitation in a centrifugal pump?
A. Electrical arcing inside the motor
B. Formation and collapse of vapor bubbles caused by inadequate suction
conditions
C. Excessive lubrication of bearings
D. A condition caused only by high discharge pressure
Correct Answer: B
Rationale:
Cavitation occurs when pressure at the pump suction falls sufficiently for liquid to
vaporize. The vapor bubbles subsequently collapse, producing noise, vibration,
reduced performance, and potential damage to the impeller.
Questions and Answers with Rationales
Latest Versions
Question 1
A steam boiler's water level is significantly below the normal operating level. What
should the custodian engineer do FIRST?
A. Immediately add cold water to the hot boiler
B. Increase the burner firing rate
C. Determine why the water level is low and follow the boiler's safe
shutdown/water-level procedure
D. Open the steam outlet valve fully
Correct Answer: C
Rationale:
A dangerously low boiler water level can expose heating surfaces and cause severe
damage or a boiler failure. The engineer should not immediately introduce cold
water into an overheated boiler, because rapid temperature changes can cause
thermal shock. The cause of the low-water condition should be investigated and the
manufacturer's/emergency operating procedure followed.
Question 2
What is the primary purpose of a boiler low-water cutoff?
A. To increase steam pressure
B. To prevent the burner from operating when the boiler water level is dangerously
low
C. To increase combustion efficiency
D. To regulate building temperature
Correct Answer: B
,Rationale:
A low-water cutoff (LWCO) is a critical boiler safety device. It shuts down the
burner when the water level falls below a safe limit, helping prevent overheating
and potentially catastrophic boiler damage.
Question 3
A centrifugal pump is running, but little or no water is being delivered. Which
condition should be checked FIRST?
A. Paint condition on the motor
B. Whether the pump is properly primed and whether the suction supply is
available
C. Room lighting
D. Thermostat calibration
Correct Answer: B
Rationale:
A centrifugal pump generally requires an adequate liquid supply and, depending on
the installation, proper priming. A closed suction valve, blocked strainer,
inadequate water supply, or loss of prime can result in little or no flow.
Question 4
What is the primary function of a pressure relief valve on a boiler?
A. Increase operating pressure
B. Remove sediment from the boiler
C. Automatically relieve excessive pressure
D. Control combustion air
Correct Answer: C
Rationale:
The pressure relief valve is a safety device designed to open when pressure
,reaches its set point, preventing pressure from exceeding the safe design limits of
the equipment.
Question 5
A boiler flame repeatedly goes out shortly after ignition. Which is the BEST initial
approach?
A. Disable the flame safeguard
B. Increase the fuel pressure without testing
C. Investigate fuel supply, ignition, combustion air, and flame-sensing/safety
controls
D. Permanently bypass the safety control
Correct Answer: C
Rationale:
Repeated flame failure can result from inadequate fuel, ignition problems,
insufficient combustion air, dirty burners, flame-sensing problems, or control
faults. Safety controls should never be bypassed merely to keep equipment
operating.
Question 6
What is the purpose of a steam trap?
A. To increase steam pressure
B. To remove condensate and non-condensable gases while retaining steam as
designed
C. To introduce cold water into the boiler
D. To increase burner output
Correct Answer: B
Rationale:
Steam traps automatically discharge condensate and, depending on trap design, air
, and other non-condensables from steam systems while minimizing the loss of live
steam.
Question 7
A water gauge glass on a steam boiler provides the engineer with information
about:
A. Fuel pressure
B. Boiler water level
C. Steam temperature only
D. Combustion-air pressure
Correct Answer: B
Rationale:
The gauge glass provides a direct visual indication of the boiler's water level.
Maintaining the correct water level is essential for safe boiler operation.
Question 8
What is cavitation in a centrifugal pump?
A. Electrical arcing inside the motor
B. Formation and collapse of vapor bubbles caused by inadequate suction
conditions
C. Excessive lubrication of bearings
D. A condition caused only by high discharge pressure
Correct Answer: B
Rationale:
Cavitation occurs when pressure at the pump suction falls sufficiently for liquid to
vaporize. The vapor bubbles subsequently collapse, producing noise, vibration,
reduced performance, and potential damage to the impeller.
