Z-51 TEST 2025 LATEST 400 REAL EXAM
QUESTIONS AND CORRECT ANSWERS/
Z-51 REFRIGERATION TEST EXAM
Efficiency of the refrigerant cycle is affected by the operations of the condenser. Of the
following, a more efficient centrifugal compressor operation results from: - answers
Lowering the condensing pressure
The heat removed from the refrigerant in a condenser is: - answers 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 NYC Fire Code, you must ensure that the containers: -
answers Are approved by the US Dept. of Transportation
Which of the following best describes how the cylinder unloader works? - answers 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: - answers Cool the
motor
The amount of refrigerant that flows through the orifices of an economizer is determined
by the: - answers Differences between the high side and low side pressure
The installation of an inline refrigerant cleaning system is advisable: - answers To
remove impurities from the system
The type of refrigerant system that is least likely to leak refrigerant into the building
space that are being cooled: - answers Indirect system
The suction pressure of a reciprocating compressor is 65 PSIG. The discharge pressure
of this compressor is 120 PSIG. The atmospheric is 14.7 PSI. The compression ratio for
the given condition is closest to: - answers 1.69
A superheated vapor is: - answers 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: - answers A faulty cooling tower
water level controller
A centrifugal water pump is known as a lift pump when the: - answers The water supply
to the pump suction inlet is below the pump level
,A TXV is used to maintain constant: - answers Evaporator superheat
The chilled water supply to the building is 55 deg F. If the chiller is being used for
human comfort, should you be concerned about this, and why? - answers Yes, this
temp is too high for human comfort purposes
The packing gland of a centrifugal pump serves to: - answers The drip part of the
packing gland gives evidence that there is water in the pump
Capacity control of reciprocating hermetic compressor is typically achieved through: -
answers Operation of the hot gas bypass valve
The most important reason to sub-cool the refrigerant in the condenser is to ensure that:
- answers A pure liquid refrigerant will enter the metering device
A refrigeration engineer is logging readings 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? - answers An
expansion valve that is open too wide
A low side float valve is used to maintain: - answers The level of the refrigerant in the
evaporator
Regarding fire safety, which ASHRAE refrigerant safety classification indicates no
flammability and lower toxicity? - answers A1
When an expansion valve is operating properly, at the end of the evaporator will
contain: - answers Only superheated vapor
What information is not contained in a Material Safety Data Sheet? - answers Cost of
the material
In a steam turbine, what is the function of the Kingsbury thrust bearing? - answers
Maintain axial positioning of the rotor shaft
A centrifugal water pump is considered to the fully primed when? - answers 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? - answers 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? -
answers 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: - answers Where no liquid refrigerant is present
All liquid has been recovered from a system to be overhauled, the system: - answers
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? - answers 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? - answers 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: - answers 323
What device protects the steam turbine from excessive speed? - answers 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: - answers 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: - answers Ammonia
Of what characteristics is ASHRAE refrigerant safety group classification system: -
answers 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: - answers Recycling
Information about the physical and chemical properties of a hazardous material can be
found in: - answers Material Safety Data Sheet
What is the function of the turbine auxiliary oil pump? - answers Establish oil pressure
during turbine start up
, The rupture disc for a low pressure centrifugal refrigeration machine is normally located
on the: - answers Compressor suction
What is the primary reason ribbed metal piping is used for electrical wires connected to
the refrigeration system shown below? - answers It allows for flexibility and accounts for
vibrations
A multi cylinder reciprocating compressor uses cylinder unloaders to regulate capacity,
what would not occur if some of the unloaders fail to operate when needed? - answers
The chill water temperature will increase
As shown in the picture below, the suction gauge of a condenser water pump reads 55
PSI. The pipe supplying the pump is 75 feet long and 12 inches in diameter.
Approximately, how many gallons of water do you expect to obtain if the pipe is drained
completely? - answers 440
A water chiller system uses refrigerant R-123. A leak in the evaporator shell may result
in: - answers A higher than normal high side pressure
Capacitors are used on refrigeration motors. Of the following, the function of these
devices is to: - answers Store electrical chargers during starting and running the motor
Of the following, centrifugal refrigerant machine is best characterized by: - answers A
high volume, low pressure machine
Which of the following ASHRAE refrigerant safety classifications is the most flammable?
- answers A3
Which of the following correctly describes the object in the picture below? - answers
Standpipe hose outlet, to put out fires in case of emergency
Modern compressors usually seal the rotating shaft as it exits the compressor housing a
spring - answers Metal or carbon
The British Thermal Unit (BTU) is the measurement of heat of energy. If 10 BTU's are
transferred to 10 pounds of water, the water temperature increase will be closest to: -
answers 1 deg F
A reciprocating compressor cylinder has a 10 inches bore and 14 inches stroke. The
volume of the refrigerant , in cubic inches, will be closer to: - answers 1099
An electrically operated control requires 24 volts to operate. To change the available
110 volts to 24 volts - answers Transformer
QUESTIONS AND CORRECT ANSWERS/
Z-51 REFRIGERATION TEST EXAM
Efficiency of the refrigerant cycle is affected by the operations of the condenser. Of the
following, a more efficient centrifugal compressor operation results from: - answers
Lowering the condensing pressure
The heat removed from the refrigerant in a condenser is: - answers 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 NYC Fire Code, you must ensure that the containers: -
answers Are approved by the US Dept. of Transportation
Which of the following best describes how the cylinder unloader works? - answers 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: - answers Cool the
motor
The amount of refrigerant that flows through the orifices of an economizer is determined
by the: - answers Differences between the high side and low side pressure
The installation of an inline refrigerant cleaning system is advisable: - answers To
remove impurities from the system
The type of refrigerant system that is least likely to leak refrigerant into the building
space that are being cooled: - answers Indirect system
The suction pressure of a reciprocating compressor is 65 PSIG. The discharge pressure
of this compressor is 120 PSIG. The atmospheric is 14.7 PSI. The compression ratio for
the given condition is closest to: - answers 1.69
A superheated vapor is: - answers 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: - answers A faulty cooling tower
water level controller
A centrifugal water pump is known as a lift pump when the: - answers The water supply
to the pump suction inlet is below the pump level
,A TXV is used to maintain constant: - answers Evaporator superheat
The chilled water supply to the building is 55 deg F. If the chiller is being used for
human comfort, should you be concerned about this, and why? - answers Yes, this
temp is too high for human comfort purposes
The packing gland of a centrifugal pump serves to: - answers The drip part of the
packing gland gives evidence that there is water in the pump
Capacity control of reciprocating hermetic compressor is typically achieved through: -
answers Operation of the hot gas bypass valve
The most important reason to sub-cool the refrigerant in the condenser is to ensure that:
- answers A pure liquid refrigerant will enter the metering device
A refrigeration engineer is logging readings 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? - answers An
expansion valve that is open too wide
A low side float valve is used to maintain: - answers The level of the refrigerant in the
evaporator
Regarding fire safety, which ASHRAE refrigerant safety classification indicates no
flammability and lower toxicity? - answers A1
When an expansion valve is operating properly, at the end of the evaporator will
contain: - answers Only superheated vapor
What information is not contained in a Material Safety Data Sheet? - answers Cost of
the material
In a steam turbine, what is the function of the Kingsbury thrust bearing? - answers
Maintain axial positioning of the rotor shaft
A centrifugal water pump is considered to the fully primed when? - answers 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? - answers 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? -
answers 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: - answers Where no liquid refrigerant is present
All liquid has been recovered from a system to be overhauled, the system: - answers
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? - answers 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? - answers 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: - answers 323
What device protects the steam turbine from excessive speed? - answers 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: - answers 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: - answers Ammonia
Of what characteristics is ASHRAE refrigerant safety group classification system: -
answers 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: - answers Recycling
Information about the physical and chemical properties of a hazardous material can be
found in: - answers Material Safety Data Sheet
What is the function of the turbine auxiliary oil pump? - answers Establish oil pressure
during turbine start up
, The rupture disc for a low pressure centrifugal refrigeration machine is normally located
on the: - answers Compressor suction
What is the primary reason ribbed metal piping is used for electrical wires connected to
the refrigeration system shown below? - answers It allows for flexibility and accounts for
vibrations
A multi cylinder reciprocating compressor uses cylinder unloaders to regulate capacity,
what would not occur if some of the unloaders fail to operate when needed? - answers
The chill water temperature will increase
As shown in the picture below, the suction gauge of a condenser water pump reads 55
PSI. The pipe supplying the pump is 75 feet long and 12 inches in diameter.
Approximately, how many gallons of water do you expect to obtain if the pipe is drained
completely? - answers 440
A water chiller system uses refrigerant R-123. A leak in the evaporator shell may result
in: - answers A higher than normal high side pressure
Capacitors are used on refrigeration motors. Of the following, the function of these
devices is to: - answers Store electrical chargers during starting and running the motor
Of the following, centrifugal refrigerant machine is best characterized by: - answers A
high volume, low pressure machine
Which of the following ASHRAE refrigerant safety classifications is the most flammable?
- answers A3
Which of the following correctly describes the object in the picture below? - answers
Standpipe hose outlet, to put out fires in case of emergency
Modern compressors usually seal the rotating shaft as it exits the compressor housing a
spring - answers Metal or carbon
The British Thermal Unit (BTU) is the measurement of heat of energy. If 10 BTU's are
transferred to 10 pounds of water, the water temperature increase will be closest to: -
answers 1 deg F
A reciprocating compressor cylinder has a 10 inches bore and 14 inches stroke. The
volume of the refrigerant , in cubic inches, will be closer to: - answers 1099
An electrically operated control requires 24 volts to operate. To change the available
110 volts to 24 volts - answers Transformer
