FDNY WRITTEN Z51 EXAM REVISION WITH CORRECT ANSWERS
2025. SAMPLE EXAM REVISION PRACTICE QUESTIONS WITH
CORRECT ANSWERS (2025 UPDATE)
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
,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
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
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
2025. SAMPLE EXAM REVISION PRACTICE QUESTIONS WITH
CORRECT ANSWERS (2025 UPDATE)
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
,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
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
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
