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UNIT 13 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
13-1) What is the only thing all compressors must pump?
13-2) List the major types of compressors by mechanical design.
Reciprocating, rotary, scroll, screw, centrifugal
13-3) Explain the difference between a positive displacement compressor and a non-
positive displacement compressor.
13-4) What is the function of the compressor within the refrigeration cycle?
13-5) What factors affect compressor capacity?
13-6) Why are the intake ports on low- and medium-temperature compressors larger
in size than the intake ports on air conditioning compressors?
13-7) Why are hermetic compressors designed for specific applications?
13-8) Why is more horsepower required to produce a ton of cooling at an evaporator
saturation temperature of 0°F than at 40°F?
13-9) What is the purpose of the shaft seal on an open compressor?
13-10) List two advantages of open drive compressors.
13-11) What is hermetic compressor?
13-12) What is an advantage of the semi-hermetic compressor design?
13-13) What opens and closes the valves in a reciprocating compressor?
13-14) What is the clearance volume of a reciprocating compressor?
13-15) What are some common applications for rotary compressors?
13-16) How does a rolling piston rotary compressor work?
13-17) How does a rotary-vane compressor work?
13-18) How does a scroll compressor work?
13-19) What rotates in a scroll compressor?
13-20) Explain what compliance means for scroll compressors.
13-21) Why should hermetic compressors not be operated in a vacuum?
13-22) What is the purpose of compressor capacity control?
13-23) How does a two-step scroll compressor achieve capacity reduction?
13-24) What controls the internal unloading solenoid coil of the two-step scroll?
13-25) At what two capacities can a digital scroll compressor operate?
13-26) What gives the digital scroll the appearance of varying its capacity?
13-27) What is the lowest percentage of full capacity that a digital scroll can be
operated and why?
13-28) What are the three different screw compressor types?
13-29) How are the small gaps on the screw compressor sealed?
13-30) Why is the oil separator important to screw compressors?
13-31) How does a centrifugal compressor work?
13-32) What type of systems are most centrifugal compressors used on?
13-33) How can oil be delivered to internal moving compressor parts?
13-34) What is the purpose of a crankcase heater on a compressor?
13-35) List ways to change the compressor capacity to match the system load.
13-36) Above what temperature do most refrigerant oils begin to break down
chemically?
13-37) What is the compression ratio of a compressor with a suction pressure of 110
psig and a discharge pressure of 360 psig?
13-38) Why is it incorrect to close the suction line service valve to test a compressor?
13-39) What problem can be caused if liquid refrigerant enters the compressor?
13-40) What is cylinder gas reexpansion and why is it a problem?
13-41) How can a technician tell is a failed compressor has been operating at
excessive discharge temperatures?
13-42) How can a technician determine if an operating compressor is experiencing
floodback?
