Z-51 Written Exam QUESTIONS WITH ANSWERS

Z-51 Written Exam QUESTIONS WITH
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ANSWERS

The efficiency of the refrigerant cycle is affected by the operation
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of the condenser. Of the following, a more efficient centrifugal
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compressor operation results from: |\ |\ |\ |\




A. Raising the condenser liquid level to the maximum
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B. Lowering the chilled water set point
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C. Raising the condenser head pressure
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D. Lowering the condensing pressure - CORRECT ANSWERS ✔✔D.
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Lowering the condensing pressure
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The heat removed from the refrigerant in a condenser is:
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A. Sensible and latent heat
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B. Latent heat only
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C. Radiant heat only
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D. Sensible heat only - CORRECT ANSWERS ✔✔A. Sensible and
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latent heat |\




The refrigerant unit that you have been assigned to is being
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taken out of service for a major repair. You have been assigned to
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withdraw refrigerant for storage in suitable containers. According
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,to the New York City fire code, you must ensure that the
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containers: |\




A. Do not weigh more than 200 pounds when filled
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B. Are approved by the US Department of Transportation
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C. Are approved by the OSHA Association
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D. Do not exceed 55 Gallons in capacity - CORRECT ANSWERS
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✔✔B. Are approved by the US Department of Transportation
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Which of the following best describes how the cylinder unloader
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work? |\




A. Keep in the suction valve opened while the compressor is in
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the return stroke
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B. Controls the clearance volume in the compressor with a
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solenoid |\




C. Controls the opening of the passage into the compressor with
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variable vanes |\




D. Unloads the piston to create less pressure - CORRECT
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ANSWERS ✔✔A. Keep in the suction valve opened while the |\ |\ |\ |\ |\ |\ |\ |\ |\ |\


compressor is in the return stroke |\ |\ |\ |\ |\




In the most semi Hermetic compressors, the suction vapor is
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used to: |\ |\




A. Removes oil from the motor housing
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B. Cools the motor
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,C. Minimizes oil foaming
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D. Removes oil foam from the shaft - CORRECT ANSWERS ✔✔B.
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Cools the motor |\ |\




The amount of refrigerant that flows through the orifices of a
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economizer is determined by the: |\ |\ |\ |\ |\




A. Number of economizer stages
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B. Temperature of the high side refrigerant
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C. Number of compressor stages
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D. Difference between high side and low side pressure -
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CORRECT ANSWERS ✔✔D. Difference between high side and low
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side pressure
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The installation of an inline refrigerant cleaning system is
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advisable: |\




A. For high pressure refrigerant systems
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B. To purge non-condensables
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C. For systems using toxic refrigerant
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D. To remove impurities from the system - CORRECT ANSWERS
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✔✔D. To remove impurities from the system
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The type of refrigerant system that is least likely to leak
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refrigerant into the building space that are being cooled:
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, A. The direct vented closed system
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B. The direct closed system
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C. Any system using reciprocating compressor
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D. The indirect system - CORRECT ANSWERS ✔✔D. The indirect
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system


The suction pressure of a reciprocating compressor is 65 PSIG.
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The discharge pressure of this compressor is 120 PSIG. The
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atmospheric is 14.7 PSI. The compression ratio for the given
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condition is closet to: |\ |\ |\ |\




A. 2.07
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B. 4.41
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C. 1.69
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D. 1.84 - CORRECT ANSWERS ✔✔C. 1.69
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A superheated vapor is a:
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A. Dry vapor at the saturation temperature
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B. Dry saturated vapor
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C. Dry vapor above the saturation temperature
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D. Vapor with minimal amount of included liquid - CORRECT
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ANSWERS ✔✔C. Dry vapor above the saturation temperature
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