1|Page
FDNY Z51 EXAM AND STUDY GUIDE EXAM NEWEST
2025 QUESTIONS AND VERIFIED ANSWERS (100%
CORRECT ANSWERS) ALREADY GRADED A+
The efficiency of the refrigerant cycle is affected by the operation of the
condenser. of the following. a more efficient centrifugal compressor operation
results from: - ..(ANSWER)...Lowering the condensing pressure
The heat removed from the refrigerant in a condenser is: - ..(ANSWER)...Sensible
and latent heat
The refrigerant unit that you have been assigned to is being taken out of service
for a major repair. you have been assigned to withdraw refrigerant for storage in
suitable containers. according to the new York city fire code, you must ensure
that the containers: - ..(ANSWER)...Are approved by the US department of
transportation
Which of the following best describes how the cylinder unloader work? -
..(ANSWER)...Keep in the suction valve opened while the compressor is in the
return stroke
In most semi hermetic compressors, the suction vapor is used to: -
..(ANSWER)...Cool the motor
The amount of refrigerant that flows through the orifices of a economizer is
determined by the: - ..(ANSWER)...Difference between the high side and load side
pressure
,2|Page
The installation of an inline refrigerant cleaning system is advisable: -
..(ANSWER)...To remove impurities from the system
The type of refrigerant system that is least likely to leak refrigerant into the
building space that are cooled - ..(ANSWER)...The indirect system
The suction pressure of a reciprocating compressor is 65PSIG. the discharge
pressure of this compressor is 120PSIG. the atmospheric is 14.7 PSI. the
compression ratio for the given condition is closet to: - ..(ANSWER)...1.69
A super heated vapor is a ? - ..(ANSWER)...Dry vapor above the saturation
temperature
A refrigerant engineer verifies that a condenser water pump is cavitating. of the
following the most likely cause for this condition is: - ..(ANSWER)...A faulty cooling
tower water level controller
A centrifugal water pump is known as a lift pump when the: - ..(ANSWER)...The
water supply to the pump suction inlet is below the pump level
A TXV is used to maintain constant: - ..(ANSWER)...Evaporator superheat
,3|Page
The chilled water supply to the building is 55F. if the chiller is being used for
human comfort, should you be concerned about this , and why? -
..(ANSWER)...Yes, this temperature is too high for human comfort purpose
The packing gland of a centrifugal pump serves to: - ..(ANSWER)...The drip part of
the packing gland gives evidence that there is water in the pump
Capacity control of a reciprocating hermetic compressor is typically achieved
through - ..(ANSWER)...Operation of the hot gas bypass valve
The most important reason to sub-cool the refrigerant in the condenser is to
ensure that: - ..(ANSWER)...A pure liquid refrigerant will enter the metering device
A refrigeration engineer is logging reading from a reciprocating system.
compressor discharge temperature have dropped significantly and the suction
line pressure is high. which of the following that may be causing this set of
condition. - ..(ANSWER)...An expansion valve that is open to wide
A low side float valve is used to maintain: - ..(ANSWER)...The level of the
refrigerant in the evaporator
Regarding fire safety, which ASHARE refrigerant safety classification indicates no
flammability and lower the toxicity? - ..(ANSWER)...A1
When an expansion valve is operating properly, at the end of the evaporator will
contain: - ..(ANSWER)...Only superheated vapor
, 4|Page
What information is not contained in a material safety data sheet-MSDS? -
..(ANSWER)...Cost of 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 be 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)...Lever type tubing bender
A reciprocating compressor is making a knocking sound during operation. if the
refrigerant worn parts are not causing the knocking, what is probably the cause -
..(ANSWER)...The slugging of the liquid refrigerant
In order for a refrigerant to become superheated in a section of the lowside
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 removed
FDNY Z51 EXAM AND STUDY GUIDE EXAM NEWEST
2025 QUESTIONS AND VERIFIED ANSWERS (100%
CORRECT ANSWERS) ALREADY GRADED A+
The efficiency of the refrigerant cycle is affected by the operation of the
condenser. of the following. a more efficient centrifugal compressor operation
results from: - ..(ANSWER)...Lowering the condensing pressure
The heat removed from the refrigerant in a condenser is: - ..(ANSWER)...Sensible
and latent heat
The refrigerant unit that you have been assigned to is being taken out of service
for a major repair. you have been assigned to withdraw refrigerant for storage in
suitable containers. according to the new York city fire code, you must ensure
that the containers: - ..(ANSWER)...Are approved by the US department of
transportation
Which of the following best describes how the cylinder unloader work? -
..(ANSWER)...Keep in the suction valve opened while the compressor is in the
return stroke
In most semi hermetic compressors, the suction vapor is used to: -
..(ANSWER)...Cool the motor
The amount of refrigerant that flows through the orifices of a economizer is
determined by the: - ..(ANSWER)...Difference between the high side and load side
pressure
,2|Page
The installation of an inline refrigerant cleaning system is advisable: -
..(ANSWER)...To remove impurities from the system
The type of refrigerant system that is least likely to leak refrigerant into the
building space that are cooled - ..(ANSWER)...The indirect system
The suction pressure of a reciprocating compressor is 65PSIG. the discharge
pressure of this compressor is 120PSIG. the atmospheric is 14.7 PSI. the
compression ratio for the given condition is closet to: - ..(ANSWER)...1.69
A super heated vapor is a ? - ..(ANSWER)...Dry vapor above the saturation
temperature
A refrigerant engineer verifies that a condenser water pump is cavitating. of the
following the most likely cause for this condition is: - ..(ANSWER)...A faulty cooling
tower water level controller
A centrifugal water pump is known as a lift pump when the: - ..(ANSWER)...The
water supply to the pump suction inlet is below the pump level
A TXV is used to maintain constant: - ..(ANSWER)...Evaporator superheat
,3|Page
The chilled water supply to the building is 55F. if the chiller is being used for
human comfort, should you be concerned about this , and why? -
..(ANSWER)...Yes, this temperature is too high for human comfort purpose
The packing gland of a centrifugal pump serves to: - ..(ANSWER)...The drip part of
the packing gland gives evidence that there is water in the pump
Capacity control of a reciprocating hermetic compressor is typically achieved
through - ..(ANSWER)...Operation of the hot gas bypass valve
The most important reason to sub-cool the refrigerant in the condenser is to
ensure that: - ..(ANSWER)...A pure liquid refrigerant will enter the metering device
A refrigeration engineer is logging reading from a reciprocating system.
compressor discharge temperature have dropped significantly and the suction
line pressure is high. which of the following that may be causing this set of
condition. - ..(ANSWER)...An expansion valve that is open to wide
A low side float valve is used to maintain: - ..(ANSWER)...The level of the
refrigerant in the evaporator
Regarding fire safety, which ASHARE refrigerant safety classification indicates no
flammability and lower the toxicity? - ..(ANSWER)...A1
When an expansion valve is operating properly, at the end of the evaporator will
contain: - ..(ANSWER)...Only superheated vapor
, 4|Page
What information is not contained in a material safety data sheet-MSDS? -
..(ANSWER)...Cost of 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 be 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)...Lever type tubing bender
A reciprocating compressor is making a knocking sound during operation. if the
refrigerant worn parts are not causing the knocking, what is probably the cause -
..(ANSWER)...The slugging of the liquid refrigerant
In order for a refrigerant to become superheated in a section of the lowside
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 removed
