Z51 REFRIGERATION TEST
Efficiency of the refrigerant cycle is affected by the operations 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 NYC Fire Code, you must ensure that the containers: -
ANSWER Are approved by the US Dept. of Transportation
Which of the following best describes how the cylinder unloader works? - 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 an economizer is
determined by the: - ANSWER Differences between the high side and low 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 being cooled: - ANSWER 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: - ANSWER 1.69
A superheated vapor is: - 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 55 deg F. If the chiller is being used for
human comfort, should you be concerned about this, and why? - ANSWER Yes, this
temp is too high for human comfort purposes
,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 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 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? -
ANSWER An expansion valve that is open too wide
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? - ANSWER Establish oil
pressure during turbine start up
The rupture disc for a low pressure centrifugal refrigeration machine is normally
located on the: - ANSWER Compressor suction
What is the primary reason ribbed metal piping is used for electrical wires connected
to the refrigeration system shown below? - ANSWER 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? - ANSWER The chill water temperature will increase
Efficiency of the refrigerant cycle is affected by the operations 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 NYC Fire Code, you must ensure that the containers: -
ANSWER Are approved by the US Dept. of Transportation
Which of the following best describes how the cylinder unloader works? - 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 an economizer is
determined by the: - ANSWER Differences between the high side and low 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 being cooled: - ANSWER 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: - ANSWER 1.69
A superheated vapor is: - 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 55 deg F. If the chiller is being used for
human comfort, should you be concerned about this, and why? - ANSWER Yes, this
temp is too high for human comfort purposes
,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 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 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? -
ANSWER An expansion valve that is open too wide
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? - ANSWER Establish oil
pressure during turbine start up
The rupture disc for a low pressure centrifugal refrigeration machine is normally
located on the: - ANSWER Compressor suction
What is the primary reason ribbed metal piping is used for electrical wires connected
to the refrigeration system shown below? - ANSWER 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? - ANSWER The chill water temperature will increase
