Z51 Written UPDATED Exam Questions
and CORRECT Answers
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: - Correct Answer-
Lowering the condensing pressure
The heat removed from the refrigerant in a condenser is: - Correct 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: - Correct
Answer- Are approved by the US department of transportation
Which of the following best describes how the cylinder unloader work? - Correct 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: - Correct Answer- Cool the
motor
The amount of refrigerant that flows through the orifices of a economizer is determined by
the: - Correct Answer- Difference between the high side and load side pressure
The installation of an inline refrigerant cleaning system is advisable: - Correct 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 - Correct 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: - Correct Answer- 1.69
A super heated vapor is a ? - Correct 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: - Correct Answer- A faulty cooling tower water level
controller
A centrifugal water pump is known as a lift pump when the: - Correct Answer- The water
supply to the pump suction inlet is below the pump level
A TXV is used to maintain constant: - Correct 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? - Correct Answer- Yes, this temperature is too
high for human comfort purpose
The packing gland of a centrifugal pump serves to: - Correct 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 -
Correct Answer- Operation of the hot gas bypass valve
The most important reason to sub-cool the refrigerant in the condenser is to ensure that: -
Correct 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. - Correct Answer- An expansion
valve that is open to wide
A low side float valve is used to maintain: - Correct Answer- The level of the refrigerant in
the evaporator
Regarding fire safety, which ASHARE refrigerant safety classification indicates no
flammability and lower the toxicity? - Correct Answer- A1
, When an expansion valve is operating properly, at the end of the evaporator will contain: -
Correct Answer- Only superheated vapor
What information is not contained in a material safety data sheet-MSDS? - Correct Answer-
Cost of material
In a steam turbine, what is the function of the kingsbury thrust bearing - Correct Answer-
Maintain axial positioning of the rotor shaft
A centrifugal water pump is considered to be fully primed when - Correct 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
- Correct 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 - Correct Answer- The
slugging of the liquid refrigerant
In order for a refrigerant to become superheated in a section of the lowside refrigerant line: -
Correct Answer- Where no liquid refrigerant is present
All liquid has been recovered from a system to be overhauled, the system - Correct Answer-
Should not be opened until all vapor has been removed
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 - Correct Answer- The vapor density 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 action would take? - Correct Answer- Add additional make up water
to cooling tower
and CORRECT Answers
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: - Correct Answer-
Lowering the condensing pressure
The heat removed from the refrigerant in a condenser is: - Correct 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: - Correct
Answer- Are approved by the US department of transportation
Which of the following best describes how the cylinder unloader work? - Correct 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: - Correct Answer- Cool the
motor
The amount of refrigerant that flows through the orifices of a economizer is determined by
the: - Correct Answer- Difference between the high side and load side pressure
The installation of an inline refrigerant cleaning system is advisable: - Correct 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 - Correct 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: - Correct Answer- 1.69
A super heated vapor is a ? - Correct 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: - Correct Answer- A faulty cooling tower water level
controller
A centrifugal water pump is known as a lift pump when the: - Correct Answer- The water
supply to the pump suction inlet is below the pump level
A TXV is used to maintain constant: - Correct 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? - Correct Answer- Yes, this temperature is too
high for human comfort purpose
The packing gland of a centrifugal pump serves to: - Correct 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 -
Correct Answer- Operation of the hot gas bypass valve
The most important reason to sub-cool the refrigerant in the condenser is to ensure that: -
Correct 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. - Correct Answer- An expansion
valve that is open to wide
A low side float valve is used to maintain: - Correct Answer- The level of the refrigerant in
the evaporator
Regarding fire safety, which ASHARE refrigerant safety classification indicates no
flammability and lower the toxicity? - Correct Answer- A1
, When an expansion valve is operating properly, at the end of the evaporator will contain: -
Correct Answer- Only superheated vapor
What information is not contained in a material safety data sheet-MSDS? - Correct Answer-
Cost of material
In a steam turbine, what is the function of the kingsbury thrust bearing - Correct Answer-
Maintain axial positioning of the rotor shaft
A centrifugal water pump is considered to be fully primed when - Correct 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
- Correct 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 - Correct Answer- The
slugging of the liquid refrigerant
In order for a refrigerant to become superheated in a section of the lowside refrigerant line: -
Correct Answer- Where no liquid refrigerant is present
All liquid has been recovered from a system to be overhauled, the system - Correct Answer-
Should not be opened until all vapor has been removed
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 - Correct Answer- The vapor density 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 action would take? - Correct Answer- Add additional make up water
to cooling tower
