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FDNY written z51 Questions and
Correct Answer
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:
~: Lowering the condensing pressure
The heat removed from the refrigerant in a condenser is:
~: 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:
~: Are approved by the US department of transportation
Which of the following best describes how the cylinder unloader work?
~: 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:
~: Cool the motor
The amount of refrigerant that flows through the orifices of a economizer is determined by
the:
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~: Difference between the high side and load side pressure
The installation of an inline refrigerant cleaning system is advisable:
~: 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
~: 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:
~: 1.69
A super heated vapor is a ?
~: 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:
~: A faulty cooling tower water level controller
A centrifugal water pump is known as a lift pump when the:
~: The water supply to the pump suction inlet is below the pump level
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A TXV is used to maintain constant:
~: 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?
~: Yes, this temperature is too high for human comfort purpose
The packing gland of a centrifugal pump serves to:
~: 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
~: Operation of the hot gas bypass valve
The most important reason to sub-cool the refrigerant in the condenser is to ensure that:
~: 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.
~: An expansion valve that is open to wide
A low side float valve is used to maintain:
~: The level of the refrigerant in the evaporator
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Regarding fire safety, which ASHARE refrigerant safety classification indicates no
flammability and lower the toxicity?
~: A1
When an expansion valve is operating properly, at the end of the evaporator will contain:
~: Only superheated vapor
What information is not contained in a material safety data sheet-MSDS?
~: Cost of material
In a steam turbine, what is the function of the kingsbury thrust bearing
~: Maintain axial positioning of the rotor shaft
A centrifugal water pump is considered to be fully primed when
~: 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
~: 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
~: The slugging of the liquid refrigerant
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