,NYC Custodian Engineer (Board of Education) | Civil Service
Exam Complete Test Bank
300 Practice Questions with Detailed Rationales | DCAS Exam
No. 6042 | NYC Mechanical Code, NYC Fire Code, and NYC
Building Code | 2026/2027 Update
SECTION 1: BOILER OPERATIONS & STEAM SYSTEMS (Q1–Q50)
Question 1
According to the New York City Mechanical Code, what is the maximum allowable pressure for
a boiler to be legally classified and operated as a "low-pressure" steam boiler?
A) 5 psi
B) 15 psi
C) 100 psi
D) 150 psi
Correct Answer: B
Rationale: Low-pressure steam boilers are limited to 15 psig. Any boiler operating above 15 psi
is classified as high-pressure and requires a different class of licensure and stricter operating
protocols.
Question 2
What is the primary function of the "Hartford Loop" in a steam heating system found in many
older New York City public school buildings?
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
Correct Answer: C
Rationale: The Hartford Loop is a safety piping arrangement that prevents water from being
siphoned out of the boiler if a return line breaks, protecting the crown sheet from overheating.
,Question 3
If a Custodian Engineer observes "priming" or "foaming" in the boiler sight glass, which of the
following is the most likely cause and appropriate chemical treatment?
A) Low water level; add more feedwater immediately
B) High concentration of dissolved solids or oil in the water; perform a surface blowdown
C) Excessive oxygen in the system; add sodium sulfite
D) Scale buildup on the tubes; increase the dosage of phosphates
Correct Answer: B
Rationale: Foaming is caused by impurities on the surface of the water; a surface blowdown
removes these impurities to prevent water carryover into the steam lines.
Question 4
Which specific device is mandated by NYC code to shut off the fuel supply to the burner if the
water level in the boiler drops below the lowest safe operating point?
A) The pressurertrol
B) The aqua-stat
C) The low-water cutoff
D) The OS&Y valve
Question 5
In a centrifugal pump used for chilled water circulation, what is the purpose of the "wear
rings"?
A) To provide a seal that prevents water from leaking out of the pump shaft
B) To provide a replaceable surface that maintains internal efficiency by minimizing leakage
between the discharge and suction sides
C) To hold the impeller in place on the pump shaft
D) To lubricate the bearings during high-speed operation
Correct Answer: B
Rationale: Wear rings allow the pump to maintain high pressure by sealing the gap between
the rotating impeller and the stationary housing; they are designed to be replaced as they wear
down.
, Question 6
What is the primary fuel source for most boilers in NYC public schools?
A) Coal
B) Natural gas
C) Fuel oil
D) Wood
Correct Answer: B
Rationale: Most NYC public school boilers use natural gas as their primary fuel source, though
many are dual-fuel and can switch to fuel oil (#2 or #4) during periods of high demand or supply
interruptions.
Question 7
What is the purpose of a boiler's aquastat?
A) To measure water pressure
B) To control water temperature
C) To measure steam pressure
D) To control fuel flow
Correct Answer: B
Rationale: An aquastat is a temperature control device used on hot water boilers. It senses the
water temperature and turns the burner on or off to maintain the desired setpoint. It is not
used on steam boilers (which use a pressurertrol).
Question 8
What is the purpose of a steam boiler's pressurertrol?
A) To control water temperature
B) To control steam pressure
C) To control fuel flow
D) To control water level
Correct Answer: B
Exam Complete Test Bank
300 Practice Questions with Detailed Rationales | DCAS Exam
No. 6042 | NYC Mechanical Code, NYC Fire Code, and NYC
Building Code | 2026/2027 Update
SECTION 1: BOILER OPERATIONS & STEAM SYSTEMS (Q1–Q50)
Question 1
According to the New York City Mechanical Code, what is the maximum allowable pressure for
a boiler to be legally classified and operated as a "low-pressure" steam boiler?
A) 5 psi
B) 15 psi
C) 100 psi
D) 150 psi
Correct Answer: B
Rationale: Low-pressure steam boilers are limited to 15 psig. Any boiler operating above 15 psi
is classified as high-pressure and requires a different class of licensure and stricter operating
protocols.
Question 2
What is the primary function of the "Hartford Loop" in a steam heating system found in many
older New York City public school buildings?
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
Correct Answer: C
Rationale: The Hartford Loop is a safety piping arrangement that prevents water from being
siphoned out of the boiler if a return line breaks, protecting the crown sheet from overheating.
,Question 3
If a Custodian Engineer observes "priming" or "foaming" in the boiler sight glass, which of the
following is the most likely cause and appropriate chemical treatment?
A) Low water level; add more feedwater immediately
B) High concentration of dissolved solids or oil in the water; perform a surface blowdown
C) Excessive oxygen in the system; add sodium sulfite
D) Scale buildup on the tubes; increase the dosage of phosphates
Correct Answer: B
Rationale: Foaming is caused by impurities on the surface of the water; a surface blowdown
removes these impurities to prevent water carryover into the steam lines.
Question 4
Which specific device is mandated by NYC code to shut off the fuel supply to the burner if the
water level in the boiler drops below the lowest safe operating point?
A) The pressurertrol
B) The aqua-stat
C) The low-water cutoff
D) The OS&Y valve
Question 5
In a centrifugal pump used for chilled water circulation, what is the purpose of the "wear
rings"?
A) To provide a seal that prevents water from leaking out of the pump shaft
B) To provide a replaceable surface that maintains internal efficiency by minimizing leakage
between the discharge and suction sides
C) To hold the impeller in place on the pump shaft
D) To lubricate the bearings during high-speed operation
Correct Answer: B
Rationale: Wear rings allow the pump to maintain high pressure by sealing the gap between
the rotating impeller and the stationary housing; they are designed to be replaced as they wear
down.
, Question 6
What is the primary fuel source for most boilers in NYC public schools?
A) Coal
B) Natural gas
C) Fuel oil
D) Wood
Correct Answer: B
Rationale: Most NYC public school boilers use natural gas as their primary fuel source, though
many are dual-fuel and can switch to fuel oil (#2 or #4) during periods of high demand or supply
interruptions.
Question 7
What is the purpose of a boiler's aquastat?
A) To measure water pressure
B) To control water temperature
C) To measure steam pressure
D) To control fuel flow
Correct Answer: B
Rationale: An aquastat is a temperature control device used on hot water boilers. It senses the
water temperature and turns the burner on or off to maintain the desired setpoint. It is not
used on steam boilers (which use a pressurertrol).
Question 8
What is the purpose of a steam boiler's pressurertrol?
A) To control water temperature
B) To control steam pressure
C) To control fuel flow
D) To control water level
Correct Answer: B
