NYC Custodian Engineer Exam Practice Test | 200 Questions with
Verified Answers & Rationales | DCAS Civil Service Exam Prep |
NYC DOE Custodian Engineer Certification .pdf
Boiler Operations & Steam Systems
Q1. According to the NYC Mechanical Code, what is the maximum allowable
pressure for a low-pressure steam boiler?
A) 5 psi
B) 15 psi
C) 100 psi
D) 150 psi
Answer: B) 15 psi
Rationale: Low-pressure steam boilers are legally limited to 15 psig in NYC. Any
boiler operating above this pressure is classified as high-pressure and requires a
different class of licensure and stricter operating protocols.
Q2. What is the primary function of a low-water cutoff (LWCO) on a steam
boiler?
A) Increase steam pressure
B) Shut down the burner if the water level becomes unsafe
C) Improve fuel efficiency
D) Reduce condensate flow
Answer: B) Shut down the burner if the water level becomes unsafe
Rationale: The low-water cutoff is a critical safety device mandated by NYC code.
Its primary purpose is to shut off the fuel supply to the burner if the water level
drops below the lowest safe operating point, preventing boiler damage or
explosion.
Q3. What is the primary purpose of a safety relief valve on a boiler?
A) Increase steam pressure
B) Regulate water temperature
C) Relieve excess pressure
D) Measure fuel consumption
Answer: C) Relieve excess pressure
Rationale: Safety relief valves are designed to automatically release excess
,pressure when it exceeds the maximum allowable working pressure, preventing a
catastrophic boiler explosion.
Q4. What is the purpose of a "boiler blowdown" valve?
A) To reduce steam pressure
B) To remove sediment and dissolved solids from the boiler water
C) To test the safety valve
D) To increase boiler efficiency by lowering water temperature
Answer: B) To remove sediment and dissolved solids from the boiler water
Rationale: Blowdown removes impurities (sludge, sediment, dissolved solids) that
accumulate at the bottom of the boiler. This prevents scale buildup, maintains
water quality, and improves efficiency.
Q5. What is the primary function of the "Hartford Loop" in a steam heating
system?
A) To increase the velocity of steam as it travels to the furthest radiator
B) To provide a bypass route for steam when the main header is closed
C) To prevent the boiler from losing its water level below a safe point in the event
of a leak in the return line
D) To trap air and vent it out of the system before it reaches the boiler
Answer: C) To prevent the boiler from losing its water level below a safe point in
the event of a leak in the return line
Rationale: The Hartford Loop is a safety piping arrangement that prevents the
boiler's water from being siphoned out if a return line breaks, protecting the
critical "crown sheet" from overheating and potential catastrophic failure.
Q6. A Custodian Engineer notices a faint odor of natural gas in a school boiler
room. What is the FIRST course of action?
A) Locate the main gas shut-off valve and close it
B) Open all windows and doors to ventilate the area
C) Evacuate the area and call 911 from a remote location
D) Attempt to locate the leak using a soapy water solution
Answer: C) Evacuate the area and call 911 from a remote location
Rationale: Safety is the absolute priority. Any action that could create a spark
(including using a phone or operating electrical switches) poses an ignition risk.
, Evacuation and calling from a safe remote location is the mandated first step per
FDNY safety protocols.
Q7. What device is used to control the burner operation based on steam
pressure?
A) Aquastat
B) Pressuretrol
C) Low-water cutoff
D) Thermostat
Answer: B) Pressuretrol
Rationale: A pressuretrol is a pressure-operated switch that cycles the burner on
and off to maintain the desired steam pressure within a set range.
Q8. What is the purpose of the "try lever" on a boiler safety valve?
A) To manually test the valve to ensure it opens freely
B) To lock the valve in the closed position
C) To adjust the pressure setting
D) To drain the valve
Answer: A) To manually test the valve to ensure it opens freely
Rationale: The try lever (or test lever) allows the operator to manually lift the
safety valve. This verifies that the valve is not seized and will function properly in
an overpressure event.
Q9. Which instrument is used to measure boiler operating pressure?
A) Thermostat
B) Flow switch
C) Pressure gauge
D) Hygrometer
Answer: C) Pressure gauge
Rationale: A pressure gauge is used to measure and display the steam or water
pressure inside the boiler, which is essential for safe and efficient operation.
Q10. What is the primary function of an aquastat in a boiler system?
A) To shut off the burner if water level drops too low
B) To control the burner based on water temperature
C) To relieve excess pressure
D) To measure steam pressure
Verified Answers & Rationales | DCAS Civil Service Exam Prep |
NYC DOE Custodian Engineer Certification .pdf
Boiler Operations & Steam Systems
Q1. According to the NYC Mechanical Code, what is the maximum allowable
pressure for a low-pressure steam boiler?
A) 5 psi
B) 15 psi
C) 100 psi
D) 150 psi
Answer: B) 15 psi
Rationale: Low-pressure steam boilers are legally limited to 15 psig in NYC. Any
boiler operating above this pressure is classified as high-pressure and requires a
different class of licensure and stricter operating protocols.
Q2. What is the primary function of a low-water cutoff (LWCO) on a steam
boiler?
A) Increase steam pressure
B) Shut down the burner if the water level becomes unsafe
C) Improve fuel efficiency
D) Reduce condensate flow
Answer: B) Shut down the burner if the water level becomes unsafe
Rationale: The low-water cutoff is a critical safety device mandated by NYC code.
Its primary purpose is to shut off the fuel supply to the burner if the water level
drops below the lowest safe operating point, preventing boiler damage or
explosion.
Q3. What is the primary purpose of a safety relief valve on a boiler?
A) Increase steam pressure
B) Regulate water temperature
C) Relieve excess pressure
D) Measure fuel consumption
Answer: C) Relieve excess pressure
Rationale: Safety relief valves are designed to automatically release excess
,pressure when it exceeds the maximum allowable working pressure, preventing a
catastrophic boiler explosion.
Q4. What is the purpose of a "boiler blowdown" valve?
A) To reduce steam pressure
B) To remove sediment and dissolved solids from the boiler water
C) To test the safety valve
D) To increase boiler efficiency by lowering water temperature
Answer: B) To remove sediment and dissolved solids from the boiler water
Rationale: Blowdown removes impurities (sludge, sediment, dissolved solids) that
accumulate at the bottom of the boiler. This prevents scale buildup, maintains
water quality, and improves efficiency.
Q5. What is the primary function of the "Hartford Loop" in a steam heating
system?
A) To increase the velocity of steam as it travels to the furthest radiator
B) To provide a bypass route for steam when the main header is closed
C) To prevent the boiler from losing its water level below a safe point in the event
of a leak in the return line
D) To trap air and vent it out of the system before it reaches the boiler
Answer: C) To prevent the boiler from losing its water level below a safe point in
the event of a leak in the return line
Rationale: The Hartford Loop is a safety piping arrangement that prevents the
boiler's water from being siphoned out if a return line breaks, protecting the
critical "crown sheet" from overheating and potential catastrophic failure.
Q6. A Custodian Engineer notices a faint odor of natural gas in a school boiler
room. What is the FIRST course of action?
A) Locate the main gas shut-off valve and close it
B) Open all windows and doors to ventilate the area
C) Evacuate the area and call 911 from a remote location
D) Attempt to locate the leak using a soapy water solution
Answer: C) Evacuate the area and call 911 from a remote location
Rationale: Safety is the absolute priority. Any action that could create a spark
(including using a phone or operating electrical switches) poses an ignition risk.
, Evacuation and calling from a safe remote location is the mandated first step per
FDNY safety protocols.
Q7. What device is used to control the burner operation based on steam
pressure?
A) Aquastat
B) Pressuretrol
C) Low-water cutoff
D) Thermostat
Answer: B) Pressuretrol
Rationale: A pressuretrol is a pressure-operated switch that cycles the burner on
and off to maintain the desired steam pressure within a set range.
Q8. What is the purpose of the "try lever" on a boiler safety valve?
A) To manually test the valve to ensure it opens freely
B) To lock the valve in the closed position
C) To adjust the pressure setting
D) To drain the valve
Answer: A) To manually test the valve to ensure it opens freely
Rationale: The try lever (or test lever) allows the operator to manually lift the
safety valve. This verifies that the valve is not seized and will function properly in
an overpressure event.
Q9. Which instrument is used to measure boiler operating pressure?
A) Thermostat
B) Flow switch
C) Pressure gauge
D) Hygrometer
Answer: C) Pressure gauge
Rationale: A pressure gauge is used to measure and display the steam or water
pressure inside the boiler, which is essential for safe and efficient operation.
Q10. What is the primary function of an aquastat in a boiler system?
A) To shut off the burner if water level drops too low
B) To control the burner based on water temperature
C) To relieve excess pressure
D) To measure steam pressure
