FDNY Z51 EXAM 3 2026 FULL QUESTION BANK
AND MOCK TEST WITH SOLVED ANSWERS
AND EXPLANATIONS
◉ A low side float valve is used to maintain:
Answer: The level of the refrigerant in the evaporator
◉ Regarding fire safety, which ASHRAE refrigerant safety
classification indicates no flammability and lower toxicity?
Answer: A1
◉ When an expansion valve is operating properly, at the end of the
evaporator will contain:
Answer: Only superheated vapor
◉ What information is not contained in a Material Safety Data
Sheet?
Answer: Cost of the material
◉ In a steam turbine, what is the function of the Kingsbury thrust
bearing?
Answer: Maintain axial positioning of the rotor shaft
,◉ A centrifugal water pump is considered to the fully primed when?
Answer: The pump is full of liquid
◉ Copper tubing refrigerant lines must be installed for a new
system. It is a well known service practice that tubing collapses at
bends that must be made, the refrigerant engineer should use?
Answer: Level type tubing bender
◉ A reciprocating compressor is making a knocking sound during
operation. If the refrigerant worn parts are not causing the knocking,
what probably the cause?
Answer: Slugging of the liquid refrigerant
◉ In order for a refrigerant to become superheated, it must be
heated in a section of the low side refrigerant line:
Answer: Where no liquid refrigerant is present
◉ All liquid has been recovered from a system to be overhauled, the
system:
Answer: Should not be opened until all vapor has been recovered
,◉ When a refrigerant engineer uses a portable compressor recovery
unit to remove vapor refrigerant from a refrigeration system the
removal rate of the refrigerant will gradually slow down because?
Answer: The compressor efficiency is decreasing
◉ You are the engineer running a 2000-ton (steam driven turbine)
centrifugal refrigeration system, a refrigeration system supplies
chilled water to a college campus with multiple buildings. During the
course of making your rounds, you check the 9 cell cooling tower on
the roof. You note the water level in all of the cooling tower cells is
very low. Which one of the following immediate actions would take?
Answer: Add additional make up water to the cooling tower
◉ A rooftop water cooling tower is connected to a water pump in the
building basement with a 12 inch diameter pipe. With the pipe
turned off, a pressure gauge at the pumps inlet show a pressure of
140 PSIG the height of the water column, in feet, would be closest to:
Answer: 323
◉ What device protects the steam turbine from excessive speed?
Answer: Governor assembly
◉ A refrigeration compressor has failed to turn on. The refrigeration
engineer on duty verifies that the electrical circuit to the motor,
including all switches and circuit breakers, is complete according to
, recommended service practice, the next item to be checked would
likely be the:
Answer: Temperature and pressure controls
◉ Refrigerants are characterized by their physical properties
included flashpoint, refrigeration effect, and others. Of the
refrigerants in commercial and industrial, the one with the highest
latent heat and refrigerant effect is:
Answer: Ammonia
◉ Of what characteristics is ASHRAE refrigerant safety group
classification system:
Answer: Flammability and toxicity
◉ Of the following, an example of an in line refrigerant cleaning
system that may be used with a centrifugal compressor containing
R-123 refrigerant is:
Answer: Recycling
◉ Information about the physical and chemical properties of a
hazardous material can be found in:
Answer: Material Safety Data Sheet
◉ What is the function of the turbine auxiliary oil pump?
AND MOCK TEST WITH SOLVED ANSWERS
AND EXPLANATIONS
◉ A low side float valve is used to maintain:
Answer: The level of the refrigerant in the evaporator
◉ Regarding fire safety, which ASHRAE refrigerant safety
classification indicates no flammability and lower toxicity?
Answer: A1
◉ When an expansion valve is operating properly, at the end of the
evaporator will contain:
Answer: Only superheated vapor
◉ What information is not contained in a Material Safety Data
Sheet?
Answer: Cost of the material
◉ In a steam turbine, what is the function of the Kingsbury thrust
bearing?
Answer: Maintain axial positioning of the rotor shaft
,◉ A centrifugal water pump is considered to the fully primed when?
Answer: The pump is full of liquid
◉ Copper tubing refrigerant lines must be installed for a new
system. It is a well known service practice that tubing collapses at
bends that must be made, the refrigerant engineer should use?
Answer: Level type tubing bender
◉ A reciprocating compressor is making a knocking sound during
operation. If the refrigerant worn parts are not causing the knocking,
what probably the cause?
Answer: Slugging of the liquid refrigerant
◉ In order for a refrigerant to become superheated, it must be
heated in a section of the low side refrigerant line:
Answer: Where no liquid refrigerant is present
◉ All liquid has been recovered from a system to be overhauled, the
system:
Answer: Should not be opened until all vapor has been recovered
,◉ When a refrigerant engineer uses a portable compressor recovery
unit to remove vapor refrigerant from a refrigeration system the
removal rate of the refrigerant will gradually slow down because?
Answer: The compressor efficiency is decreasing
◉ You are the engineer running a 2000-ton (steam driven turbine)
centrifugal refrigeration system, a refrigeration system supplies
chilled water to a college campus with multiple buildings. During the
course of making your rounds, you check the 9 cell cooling tower on
the roof. You note the water level in all of the cooling tower cells is
very low. Which one of the following immediate actions would take?
Answer: Add additional make up water to the cooling tower
◉ A rooftop water cooling tower is connected to a water pump in the
building basement with a 12 inch diameter pipe. With the pipe
turned off, a pressure gauge at the pumps inlet show a pressure of
140 PSIG the height of the water column, in feet, would be closest to:
Answer: 323
◉ What device protects the steam turbine from excessive speed?
Answer: Governor assembly
◉ A refrigeration compressor has failed to turn on. The refrigeration
engineer on duty verifies that the electrical circuit to the motor,
including all switches and circuit breakers, is complete according to
, recommended service practice, the next item to be checked would
likely be the:
Answer: Temperature and pressure controls
◉ Refrigerants are characterized by their physical properties
included flashpoint, refrigeration effect, and others. Of the
refrigerants in commercial and industrial, the one with the highest
latent heat and refrigerant effect is:
Answer: Ammonia
◉ Of what characteristics is ASHRAE refrigerant safety group
classification system:
Answer: Flammability and toxicity
◉ Of the following, an example of an in line refrigerant cleaning
system that may be used with a centrifugal compressor containing
R-123 refrigerant is:
Answer: Recycling
◉ Information about the physical and chemical properties of a
hazardous material can be found in:
Answer: Material Safety Data Sheet
◉ What is the function of the turbine auxiliary oil pump?
