NYC Custodian Engineer Exam – Complete Civil Service Practice
Test Bank with Verified Answers & Technical Rationales | Newest
2026
Secure a top tier score on the highly competitive New York City Department of
Education civil service hiring roster with this definitive NYC Custodian Engineer exam
preparation guide. This comprehensive test bank features realistic practice questions
with verified correct answers and detailed technical rationales covering high-pressure
boiler operations, HVAC maintenance, structural building safety, electrical systems, and
administrative labor regulations. It is an indispensable resource for facility managers
and mechanical professionals looking to pass the DCAS examination on their very first
attempt.
1. What is the primary function of a building's condensate return system in a
steam heating plant?
A. To supply fresh water to the boiler
B. To collect and return condensed steam (water) to the boiler for reuse
C. To vent air from the radiators
D. To increase steam pressure in the mains
Rationale: The condensate return system is a critical component of a steam heating plant.
It collects the water that has condensed after giving up its heat, and returns it to the boiler.
This conserves water, saves energy (as the returned water is already hot), and reduces the
need for water treatment .
2. An engineer notices a water stain on the ceiling near a sprinkler head. What is
the most appropriate first step?
A. Paint over the stain
B. Investigate the source of the leak and determine if the sprinkler head is
damaged or leaking
C. Replace the sprinkler head immediately
D. Ignore the stain and monitor it
Rationale: A water stain near a sprinkler head could indicate a slow leak from the sprinkler
system. Left unchecked, a small leak could become a larger problem, or the sprinkler head
itself may be damaged and could fail in a fire. The source of the leak must be investigated
and corrected.
,3. The compressed air supply for a pneumatic HVAC control system is found to be
consistently low. What is the most likely cause?
A. A leaking actuator on a VAV box
B. A dirty air filter on the air compressor or a failing compressor
C. A failed thermostat
D. A stuck-open heating valve
Rationale: A system-wide low-pressure issue in a pneumatic system points to the central
air source: the compressor or its intake filter. A clogged filter restricts airflow, reducing the
compressor's output. A failed or undersized compressor can also be the cause. A single
leaking actuator would only affect the branch it is on .
4. What is the function of a fusible link on a fire door assembly?
A. To automatically close the door in response to a smoke detector.
B. To hold the fire door open and melt at a specific temperature, allowing the door
to close.
C. To provide a manual release for the door.
D. To lock the door in the closed position.
Rationale: A fusible link is a heat-sensitive device used to hold fire doors open. It consists
of two metal pieces joined by solder that melts at a predetermined temperature (e.g.,
135°F or 165°F). When the solder melts, the link separates, and the door closes by gravity
or a spring mechanism to contain the fire .
5. After a fire alarm is triggered and the FDNY has cleared the scene, the building
engineer should:
A. Reset the alarm before FDNY arrives to prevent a false alarm report.
B. Notify the principal that the system is offline.
C. Wait for the Fire Department to give the order to reset the fire alarm panel.
D. Silence the alarm and leave the system as is.
Rationale: It is a violation of fire code to reset a fire alarm panel before the Fire
Department has completed its investigation. The responding firefighters must determine
,the cause of the alarm and ensure the scene is safe before the system is restored to normal
operation .
6. A centrifugal chiller is experiencing reduced cooling capacity, and the condenser
water temperature is higher than normal. What is the most likely cause?
A. Low refrigerant charge
B. Dirty condenser tubes
C. Faulty expansion valve
D. Compressor failure
Rationale: Elevated condenser water temperature is a common indicator of reduced heat
transfer. This is often due to fouling or scaling on the inside of the condenser tubes. Dirt
and scale act as an insulator, preventing the heat from the refrigerant from transferring to
the condenser water, thus reducing the chiller's efficiency .
7. What is the purpose of a cooling tower in a building's HVAC system?
A. To cool the refrigerant
B. To reject heat from the condenser water to the atmosphere
C. To supply chilled water to the building
D. To provide ventilation air
Rationale: Cooling towers are a key component of water-cooled chiller systems. They reject
the heat absorbed by the condenser water into the atmosphere, primarily through the
process of evaporation. This allows the chiller to continue removing heat from the
building's chilled water loop .
8. What is the most important preventive maintenance task for an Air Handling
Unit (AHU)?
A. Lubricating the motor bearings
B. Changing the air filters regularly
C. Painting the exterior
D. Calibrating the thermostat
, Rationale: While lubrication, painting, and calibration are valid tasks, regularly changing
the air filters is the most important preventive maintenance task for an AHU. Clogged
filters restrict airflow, reducing system efficiency, increasing energy consumption, and can
lead to motor or component failure .
9. A sump pump in a basement is running continuously. What is the most likely
cause?
A. Low water level
B. Burned-out motor
C. Stuck float switch
D. Clogged discharge pipe
Rationale: A sump pump that runs continuously is most often caused by a float switch that
is stuck in the "on" position. If the float cannot drop, it will keep the pump running even
when the water level is low. A burned-out motor would not run at all; a clogged discharge
pipe would cause the pump to run but not move water .
10. Which of the following is a key symptom of a failing capacitor on a single-
phase HVAC compressor or fan motor?
A. The motor runs but at a slower speed.
B. The motor hums but does not start, or starts slowly.
C. The motor runs faster than normal.
D. The motor trips the circuit breaker immediately.
Rationale: A failing capacitor is a common cause of motor failure. In a single-phase motor,
the capacitor provides the phase shift needed to start the motor. If the capacitor is weak or
failed, the motor may just hum when power is applied, or it may start slowly and draw
high current, leading to overheating .
11. What component of a hot-water heating system maintains constant system
pressure by accommodating water expansion?
A. Circulator pump
Test Bank with Verified Answers & Technical Rationales | Newest
2026
Secure a top tier score on the highly competitive New York City Department of
Education civil service hiring roster with this definitive NYC Custodian Engineer exam
preparation guide. This comprehensive test bank features realistic practice questions
with verified correct answers and detailed technical rationales covering high-pressure
boiler operations, HVAC maintenance, structural building safety, electrical systems, and
administrative labor regulations. It is an indispensable resource for facility managers
and mechanical professionals looking to pass the DCAS examination on their very first
attempt.
1. What is the primary function of a building's condensate return system in a
steam heating plant?
A. To supply fresh water to the boiler
B. To collect and return condensed steam (water) to the boiler for reuse
C. To vent air from the radiators
D. To increase steam pressure in the mains
Rationale: The condensate return system is a critical component of a steam heating plant.
It collects the water that has condensed after giving up its heat, and returns it to the boiler.
This conserves water, saves energy (as the returned water is already hot), and reduces the
need for water treatment .
2. An engineer notices a water stain on the ceiling near a sprinkler head. What is
the most appropriate first step?
A. Paint over the stain
B. Investigate the source of the leak and determine if the sprinkler head is
damaged or leaking
C. Replace the sprinkler head immediately
D. Ignore the stain and monitor it
Rationale: A water stain near a sprinkler head could indicate a slow leak from the sprinkler
system. Left unchecked, a small leak could become a larger problem, or the sprinkler head
itself may be damaged and could fail in a fire. The source of the leak must be investigated
and corrected.
,3. The compressed air supply for a pneumatic HVAC control system is found to be
consistently low. What is the most likely cause?
A. A leaking actuator on a VAV box
B. A dirty air filter on the air compressor or a failing compressor
C. A failed thermostat
D. A stuck-open heating valve
Rationale: A system-wide low-pressure issue in a pneumatic system points to the central
air source: the compressor or its intake filter. A clogged filter restricts airflow, reducing the
compressor's output. A failed or undersized compressor can also be the cause. A single
leaking actuator would only affect the branch it is on .
4. What is the function of a fusible link on a fire door assembly?
A. To automatically close the door in response to a smoke detector.
B. To hold the fire door open and melt at a specific temperature, allowing the door
to close.
C. To provide a manual release for the door.
D. To lock the door in the closed position.
Rationale: A fusible link is a heat-sensitive device used to hold fire doors open. It consists
of two metal pieces joined by solder that melts at a predetermined temperature (e.g.,
135°F or 165°F). When the solder melts, the link separates, and the door closes by gravity
or a spring mechanism to contain the fire .
5. After a fire alarm is triggered and the FDNY has cleared the scene, the building
engineer should:
A. Reset the alarm before FDNY arrives to prevent a false alarm report.
B. Notify the principal that the system is offline.
C. Wait for the Fire Department to give the order to reset the fire alarm panel.
D. Silence the alarm and leave the system as is.
Rationale: It is a violation of fire code to reset a fire alarm panel before the Fire
Department has completed its investigation. The responding firefighters must determine
,the cause of the alarm and ensure the scene is safe before the system is restored to normal
operation .
6. A centrifugal chiller is experiencing reduced cooling capacity, and the condenser
water temperature is higher than normal. What is the most likely cause?
A. Low refrigerant charge
B. Dirty condenser tubes
C. Faulty expansion valve
D. Compressor failure
Rationale: Elevated condenser water temperature is a common indicator of reduced heat
transfer. This is often due to fouling or scaling on the inside of the condenser tubes. Dirt
and scale act as an insulator, preventing the heat from the refrigerant from transferring to
the condenser water, thus reducing the chiller's efficiency .
7. What is the purpose of a cooling tower in a building's HVAC system?
A. To cool the refrigerant
B. To reject heat from the condenser water to the atmosphere
C. To supply chilled water to the building
D. To provide ventilation air
Rationale: Cooling towers are a key component of water-cooled chiller systems. They reject
the heat absorbed by the condenser water into the atmosphere, primarily through the
process of evaporation. This allows the chiller to continue removing heat from the
building's chilled water loop .
8. What is the most important preventive maintenance task for an Air Handling
Unit (AHU)?
A. Lubricating the motor bearings
B. Changing the air filters regularly
C. Painting the exterior
D. Calibrating the thermostat
, Rationale: While lubrication, painting, and calibration are valid tasks, regularly changing
the air filters is the most important preventive maintenance task for an AHU. Clogged
filters restrict airflow, reducing system efficiency, increasing energy consumption, and can
lead to motor or component failure .
9. A sump pump in a basement is running continuously. What is the most likely
cause?
A. Low water level
B. Burned-out motor
C. Stuck float switch
D. Clogged discharge pipe
Rationale: A sump pump that runs continuously is most often caused by a float switch that
is stuck in the "on" position. If the float cannot drop, it will keep the pump running even
when the water level is low. A burned-out motor would not run at all; a clogged discharge
pipe would cause the pump to run but not move water .
10. Which of the following is a key symptom of a failing capacitor on a single-
phase HVAC compressor or fan motor?
A. The motor runs but at a slower speed.
B. The motor hums but does not start, or starts slowly.
C. The motor runs faster than normal.
D. The motor trips the circuit breaker immediately.
Rationale: A failing capacitor is a common cause of motor failure. In a single-phase motor,
the capacitor provides the phase shift needed to start the motor. If the capacitor is weak or
failed, the motor may just hum when power is applied, or it may start slowly and draw
high current, leading to overheating .
11. What component of a hot-water heating system maintains constant system
pressure by accommodating water expansion?
A. Circulator pump
