Z-51 REFRIGERATION FINAL PAPER 2025/2026 QUESTIONS
WITH ANSWERS GRADED A+
✔✔In order for a refrigerant to become superheated, it must be heated in a section of
the low side refrigerant line: - ✔✔Where no liquid refrigerant is present
✔✔All liquid has been recovered from a system to be overhauled, the system: -
✔✔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? - ✔✔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? - ✔✔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: - ✔✔323
✔✔What device protects the steam turbine from excessive speed? - ✔✔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: - ✔✔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: - ✔✔Ammonia
✔✔Of what characteristics is ASHRAE refrigerant safety group classification system: -
✔✔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: - ✔✔Recycling
,✔✔Information about the physical and chemical properties of a hazardous material can
be found in: - ✔✔Material Safety Data Sheet
✔✔What is the function of the turbine auxiliary oil pump? - ✔✔Establish oil pressure
during turbine start up
✔✔The rupture disc for a low pressure centrifugal refrigeration machine is normally
located on the: - ✔✔Compressor suction
✔✔What is the primary reason ribbed metal piping is used for electrical wires connected
to the refrigeration system shown below? - ✔✔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? -
✔✔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? - ✔✔440
✔✔A water chiller system uses refrigerant R-123. A leak in the evaporator shell may
result in: - ✔✔A higher than normal high side pressure
✔✔Capacitors are used on refrigeration motors. Of the following, the function of these
devices is to: - ✔✔Store electrical chargers during starting and running the motor
✔✔Of the following, centrifugal refrigerant machine is best characterized by: - ✔✔A high
volume, low pressure machine
✔✔Which of the following ASHRAE refrigerant safety classifications is the most
flammable? - ✔✔A3
✔✔Which of the following correctly describes the object in the picture below? -
✔✔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 - ✔✔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:
- ✔✔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: - ✔✔1099
✔✔An electrically operated control requires 24 volts to operate. To change the available
110 volts to 24 volts - ✔✔Transformer
✔✔In an indirect refrigeration system, of the following, the one that would not be used
as a cooling medium for the building spaces being cooled is: - ✔✔R-22
✔✔On a steam turbine, what would cause the atmospheric valve to open? - ✔✔All
answers (low vacuum in the surface condenser, leaking tubes in the surface condenser,
dirty tubes in the surface condenser)
✔✔You are the engineer running a 2000-ton (steam driven turbine) centrifugal
rerigeration system, a refrigeration system supplies chilled water to a college campus
with multiple buildings. Making your rounds, you notice that the condenser water pump
#1 is making a lot of noise, the discharger guage reading of the condenser water pump
is fluctuating drastically, and motor of the condenser pump #1 is running very hot.
Which of the following would you take: - ✔✔Turn on pump #2, shut off pump #1, and
troubleshoot pump #1
✔✔Electric devices may be used to provide built in defrosting of refrigeration machine
evaporator units. These devices are classified as? - ✔✔Resistors
✔✔The flash point of a compressor lubricating oil: - ✔✔Should be higher than the
compression temperature
✔✔The primary way of achieving capacity control of a centrifugal compressor is by: -
✔✔Adjustment of the impeller inlet pre-rotation vanes
✔✔Cooling tower water requires the addition of chemical additives in order to: -
✔✔Reduce the formation of scale and algae
✔✔In the picture below describes the equipment's function: - ✔✔Remove non-
condensables from the condenser
✔✔The viscosity of lubrication oil is described by a number. A low viscosity number
describes oil that: - ✔✔Flows easily
✔✔The most likely reason for refrigeration engineer to use a psychrometer is to
measure: - ✔✔Relative humidity level of the atmosphere
WITH ANSWERS GRADED A+
✔✔In order for a refrigerant to become superheated, it must be heated in a section of
the low side refrigerant line: - ✔✔Where no liquid refrigerant is present
✔✔All liquid has been recovered from a system to be overhauled, the system: -
✔✔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? - ✔✔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? - ✔✔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: - ✔✔323
✔✔What device protects the steam turbine from excessive speed? - ✔✔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: - ✔✔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: - ✔✔Ammonia
✔✔Of what characteristics is ASHRAE refrigerant safety group classification system: -
✔✔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: - ✔✔Recycling
,✔✔Information about the physical and chemical properties of a hazardous material can
be found in: - ✔✔Material Safety Data Sheet
✔✔What is the function of the turbine auxiliary oil pump? - ✔✔Establish oil pressure
during turbine start up
✔✔The rupture disc for a low pressure centrifugal refrigeration machine is normally
located on the: - ✔✔Compressor suction
✔✔What is the primary reason ribbed metal piping is used for electrical wires connected
to the refrigeration system shown below? - ✔✔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? -
✔✔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? - ✔✔440
✔✔A water chiller system uses refrigerant R-123. A leak in the evaporator shell may
result in: - ✔✔A higher than normal high side pressure
✔✔Capacitors are used on refrigeration motors. Of the following, the function of these
devices is to: - ✔✔Store electrical chargers during starting and running the motor
✔✔Of the following, centrifugal refrigerant machine is best characterized by: - ✔✔A high
volume, low pressure machine
✔✔Which of the following ASHRAE refrigerant safety classifications is the most
flammable? - ✔✔A3
✔✔Which of the following correctly describes the object in the picture below? -
✔✔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 - ✔✔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:
- ✔✔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: - ✔✔1099
✔✔An electrically operated control requires 24 volts to operate. To change the available
110 volts to 24 volts - ✔✔Transformer
✔✔In an indirect refrigeration system, of the following, the one that would not be used
as a cooling medium for the building spaces being cooled is: - ✔✔R-22
✔✔On a steam turbine, what would cause the atmospheric valve to open? - ✔✔All
answers (low vacuum in the surface condenser, leaking tubes in the surface condenser,
dirty tubes in the surface condenser)
✔✔You are the engineer running a 2000-ton (steam driven turbine) centrifugal
rerigeration system, a refrigeration system supplies chilled water to a college campus
with multiple buildings. Making your rounds, you notice that the condenser water pump
#1 is making a lot of noise, the discharger guage reading of the condenser water pump
is fluctuating drastically, and motor of the condenser pump #1 is running very hot.
Which of the following would you take: - ✔✔Turn on pump #2, shut off pump #1, and
troubleshoot pump #1
✔✔Electric devices may be used to provide built in defrosting of refrigeration machine
evaporator units. These devices are classified as? - ✔✔Resistors
✔✔The flash point of a compressor lubricating oil: - ✔✔Should be higher than the
compression temperature
✔✔The primary way of achieving capacity control of a centrifugal compressor is by: -
✔✔Adjustment of the impeller inlet pre-rotation vanes
✔✔Cooling tower water requires the addition of chemical additives in order to: -
✔✔Reduce the formation of scale and algae
✔✔In the picture below describes the equipment's function: - ✔✔Remove non-
condensables from the condenser
✔✔The viscosity of lubrication oil is described by a number. A low viscosity number
describes oil that: - ✔✔Flows easily
✔✔The most likely reason for refrigeration engineer to use a psychrometer is to
measure: - ✔✔Relative humidity level of the atmosphere
