Z-51 REFRIGERATION TEST Exam Questions And Answers 2025 Update. (2025)

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Z-51 REFRIGERATION TEST Exam
Questions And Answers 2025 Update.

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

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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

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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

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