NYC Custodian Engineer Exam Practice Test (NEW VERSION) | Real
Updated Questions & Answers | NYC DOB License Study Guide |
LATEST UPDATE THIS YEAR.pdf Overview Prepare for the New York
City Custodian Engineer License Examination
SECTION 1: BOILER OPERATIONS & MAINTENANCE
Question 1
According to the NYC Mechanical Code, what is the maximum allowable
pressure for a boiler to be legally classified as a "low-pressure" steam
boiler?
• A) 5 psi
• B) 15 psi
• C) 100 psi
• D) 150 psi
Answer: B) 15 psi
Rationale: Under NYC Construction Code and DOB rules, a low-pressure
boiler operates at a steam pressure of 15 psi or less. Any boiler operating
above 15 psi is classified as high-pressure and requires a different class of
licensure and stricter operating protocols .
Question 2
Which boiler safety device is designed to prevent excessive pressure from
developing inside a boiler?
• A) Expansion tank
• B) Pressure gauge
• C) Safety relief valve
• D) Feedwater pump
,Answer: C) Safety relief valve
Rationale: Safety relief valves automatically release excess pressure to
prevent boiler explosions when pressure exceeds the safe operating limit.
The valve lifts at a predetermined pressure setting, venting excess steam to
the atmosphere .
Question 3
What is the primary purpose of a low-water cutoff 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 mandated safety device that shuts off
the fuel supply to the burner if the water level drops below the lowest safe
operating point, preventing catastrophic dry-firing and boiler explosion .
Question 4
What is the maximum allowable working pressure (MAWP) for a low-
pressure steam boiler under ASME and NYC codes?
• A) 5 psi
• B) 10 psi
• C) 15 psi
• D) 20 psi
Answer: C) 15 psi
,Rationale: Low-pressure steam boilers are limited to 15 psig (pounds per
square inch gauge). This is a fundamental code requirement that
distinguishes low-pressure from high-pressure boiler operation .
Question 5
If the water level inside a low-pressure steam boiler drops out of sight
below the bottom of the gauge glass while the burner is actively firing,
what immediate emergency action must the Custodian Engineer execute?
• A) Immediately open the city water supply bypass to flood the boiler
with cold water
• B) Shut off the fuel supply to the burner immediately, allow the boiler
to cool down naturally, and inspect for thermal structural damage
• C) Turn down the thermostat but leave the burner running
• D) Blow down the water column to see if the level returns
Answer: B) Shut off the fuel supply to the burner immediately, allow the
boiler to cool down naturally, and inspect for thermal structural damage
Rationale: Adding cold water to a hot, dry boiler causes instantaneous
thermal shock and metal contraction, which can trigger a catastrophic boiler
explosion. The fuel must be shut off immediately, and the unit must cool
before any water is introduced .
Question 6
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
water from being siphoned out of the boiler if a return line breaks,
protecting the crown sheet from overheating .
Question 7
A boiler's pressuretrol is designed to:
• A) Control burner firing to maintain steam pressure
• B) Measure water temperature
• C) Detect flue gas temperature
• D) Monitor fuel oil viscosity
Answer: A) Control burner firing to maintain steam pressure
Rationale: A pressuretrol (pressure controller) regulates burner operation
by turning the burner on and off to maintain the desired steam pressure
within the boiler's operating range .
Question 8
A Custodian Engineer observes "priming" or "foaming" in the boiler sight
glass. What is the most likely cause and appropriate response?
Updated Questions & Answers | NYC DOB License Study Guide |
LATEST UPDATE THIS YEAR.pdf Overview Prepare for the New York
City Custodian Engineer License Examination
SECTION 1: BOILER OPERATIONS & MAINTENANCE
Question 1
According to the NYC Mechanical Code, what is the maximum allowable
pressure for a boiler to be legally classified as a "low-pressure" steam
boiler?
• A) 5 psi
• B) 15 psi
• C) 100 psi
• D) 150 psi
Answer: B) 15 psi
Rationale: Under NYC Construction Code and DOB rules, a low-pressure
boiler operates at a steam pressure of 15 psi or less. Any boiler operating
above 15 psi is classified as high-pressure and requires a different class of
licensure and stricter operating protocols .
Question 2
Which boiler safety device is designed to prevent excessive pressure from
developing inside a boiler?
• A) Expansion tank
• B) Pressure gauge
• C) Safety relief valve
• D) Feedwater pump
,Answer: C) Safety relief valve
Rationale: Safety relief valves automatically release excess pressure to
prevent boiler explosions when pressure exceeds the safe operating limit.
The valve lifts at a predetermined pressure setting, venting excess steam to
the atmosphere .
Question 3
What is the primary purpose of a low-water cutoff 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 mandated safety device that shuts off
the fuel supply to the burner if the water level drops below the lowest safe
operating point, preventing catastrophic dry-firing and boiler explosion .
Question 4
What is the maximum allowable working pressure (MAWP) for a low-
pressure steam boiler under ASME and NYC codes?
• A) 5 psi
• B) 10 psi
• C) 15 psi
• D) 20 psi
Answer: C) 15 psi
,Rationale: Low-pressure steam boilers are limited to 15 psig (pounds per
square inch gauge). This is a fundamental code requirement that
distinguishes low-pressure from high-pressure boiler operation .
Question 5
If the water level inside a low-pressure steam boiler drops out of sight
below the bottom of the gauge glass while the burner is actively firing,
what immediate emergency action must the Custodian Engineer execute?
• A) Immediately open the city water supply bypass to flood the boiler
with cold water
• B) Shut off the fuel supply to the burner immediately, allow the boiler
to cool down naturally, and inspect for thermal structural damage
• C) Turn down the thermostat but leave the burner running
• D) Blow down the water column to see if the level returns
Answer: B) Shut off the fuel supply to the burner immediately, allow the
boiler to cool down naturally, and inspect for thermal structural damage
Rationale: Adding cold water to a hot, dry boiler causes instantaneous
thermal shock and metal contraction, which can trigger a catastrophic boiler
explosion. The fuel must be shut off immediately, and the unit must cool
before any water is introduced .
Question 6
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
water from being siphoned out of the boiler if a return line breaks,
protecting the crown sheet from overheating .
Question 7
A boiler's pressuretrol is designed to:
• A) Control burner firing to maintain steam pressure
• B) Measure water temperature
• C) Detect flue gas temperature
• D) Monitor fuel oil viscosity
Answer: A) Control burner firing to maintain steam pressure
Rationale: A pressuretrol (pressure controller) regulates burner operation
by turning the burner on and off to maintain the desired steam pressure
within the boiler's operating range .
Question 8
A Custodian Engineer observes "priming" or "foaming" in the boiler sight
glass. What is the most likely cause and appropriate response?
