NYC Custodian Engineer Exam
2026/2027 | Complete Practice Test Bank
& 300 Questions with Answers and
Rationales Guaranteed Pass (GRADED
A+)
1. What is the primary purpose of a boiler safety valve?
A. Increase steam pressure
B. Regulate water temperature
C. Release excess pressure when a predetermined limit is
reached
D. Increase combustion efficiency
Rationale: A safety valve protects the boiler and connected
system from excessive pressure by automatically relieving
pressure when its set point is reached.
2. Which instrument is commonly used to measure boiler
steam pressure?
A. Thermocouple
B. Hydrometer
C. Pressure gauge
D. Tachometer
Rationale: A pressure gauge provides a direct indication of the
pressure inside the boiler or steam system.
3. What is the primary function of a boiler burner?
,A. Remove dissolved solids
B. Provide controlled combustion to generate heat
C. Reduce steam pressure
D. Remove condensate
Rationale: The burner mixes fuel and combustion air and
produces controlled combustion that transfers heat to the boiler
water.
4. What should an engineer do if a boiler's water level
suddenly becomes dangerously low?
A. Immediately add cold water
B. Increase burner firing
C. Follow the emergency shutdown procedure
D. Increase steam pressure
Rationale: A dangerously low water condition can expose
heating surfaces and cause severe damage. The appropriate
response is to follow the established emergency procedure
rather than adding water indiscriminately.
5. What is the purpose of a low-water cutoff?
A. Increase water temperature
B. Prevent burner operation when the boiler water level is
dangerously low
C. Increase steam pressure
D. Remove sediment
Rationale: A low-water cutoff is a safety control designed to
shut down the burner when the water level falls below a safe
operating point.
,6. What is condensate?
A. Fresh boiler feedwater
B. Fuel vapor
C. Water formed when steam loses heat and condenses
D. Compressed air
Rationale: When steam transfers heat to another surface or
medium, it cools and changes back into liquid water called
condensate.
7. What is the purpose of a steam trap?
A. Increase steam pressure
B. Add chemicals to boiler water
C. Remove condensate while limiting the loss of live steam
D. Increase burner temperature
Rationale: Steam traps automatically discharge condensate and
non-condensable gases while helping retain usable steam in the
system.
8. Why is boiler water treatment important?
A. To increase fuel consumption
B. To make the boiler heavier
C. To reduce scale, corrosion, and other water-related
problems
D. To eliminate the need for inspections
Rationale: Proper water treatment helps control scale and
corrosion, improving heat transfer and protecting boiler
components.
, 9. What is scale in a boiler?
A. A type of fuel
B. A pressure-control device
C. Mineral deposits that accumulate on heating surfaces
D. A combustion gas
Rationale: Scale consists primarily of mineral deposits that can
reduce heat transfer and contribute to overheating of heating
surfaces.
10. What is the purpose of a blowdown operation?
A. Increase boiler pressure
B. Increase fuel flow
C. Remove accumulated dissolved and suspended solids from
boiler water
D. Add oxygen to the boiler
Rationale: Blowdown removes concentrated impurities from
boiler water and helps maintain acceptable water chemistry.
11. What is the main purpose of a boiler feedwater pump?
A. Remove combustion gases
B. Deliver water into the boiler at sufficient pressure
C. Reduce room temperature
D. Remove soot
Rationale: Feedwater pumps supply the boiler with water
against the pressure existing within the boiler or feedwater
system.
2026/2027 | Complete Practice Test Bank
& 300 Questions with Answers and
Rationales Guaranteed Pass (GRADED
A+)
1. What is the primary purpose of a boiler safety valve?
A. Increase steam pressure
B. Regulate water temperature
C. Release excess pressure when a predetermined limit is
reached
D. Increase combustion efficiency
Rationale: A safety valve protects the boiler and connected
system from excessive pressure by automatically relieving
pressure when its set point is reached.
2. Which instrument is commonly used to measure boiler
steam pressure?
A. Thermocouple
B. Hydrometer
C. Pressure gauge
D. Tachometer
Rationale: A pressure gauge provides a direct indication of the
pressure inside the boiler or steam system.
3. What is the primary function of a boiler burner?
,A. Remove dissolved solids
B. Provide controlled combustion to generate heat
C. Reduce steam pressure
D. Remove condensate
Rationale: The burner mixes fuel and combustion air and
produces controlled combustion that transfers heat to the boiler
water.
4. What should an engineer do if a boiler's water level
suddenly becomes dangerously low?
A. Immediately add cold water
B. Increase burner firing
C. Follow the emergency shutdown procedure
D. Increase steam pressure
Rationale: A dangerously low water condition can expose
heating surfaces and cause severe damage. The appropriate
response is to follow the established emergency procedure
rather than adding water indiscriminately.
5. What is the purpose of a low-water cutoff?
A. Increase water temperature
B. Prevent burner operation when the boiler water level is
dangerously low
C. Increase steam pressure
D. Remove sediment
Rationale: A low-water cutoff is a safety control designed to
shut down the burner when the water level falls below a safe
operating point.
,6. What is condensate?
A. Fresh boiler feedwater
B. Fuel vapor
C. Water formed when steam loses heat and condenses
D. Compressed air
Rationale: When steam transfers heat to another surface or
medium, it cools and changes back into liquid water called
condensate.
7. What is the purpose of a steam trap?
A. Increase steam pressure
B. Add chemicals to boiler water
C. Remove condensate while limiting the loss of live steam
D. Increase burner temperature
Rationale: Steam traps automatically discharge condensate and
non-condensable gases while helping retain usable steam in the
system.
8. Why is boiler water treatment important?
A. To increase fuel consumption
B. To make the boiler heavier
C. To reduce scale, corrosion, and other water-related
problems
D. To eliminate the need for inspections
Rationale: Proper water treatment helps control scale and
corrosion, improving heat transfer and protecting boiler
components.
, 9. What is scale in a boiler?
A. A type of fuel
B. A pressure-control device
C. Mineral deposits that accumulate on heating surfaces
D. A combustion gas
Rationale: Scale consists primarily of mineral deposits that can
reduce heat transfer and contribute to overheating of heating
surfaces.
10. What is the purpose of a blowdown operation?
A. Increase boiler pressure
B. Increase fuel flow
C. Remove accumulated dissolved and suspended solids from
boiler water
D. Add oxygen to the boiler
Rationale: Blowdown removes concentrated impurities from
boiler water and helps maintain acceptable water chemistry.
11. What is the main purpose of a boiler feedwater pump?
A. Remove combustion gases
B. Deliver water into the boiler at sufficient pressure
C. Reduce room temperature
D. Remove soot
Rationale: Feedwater pumps supply the boiler with water
against the pressure existing within the boiler or feedwater
system.
