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20 Cards in this Set
- Front
- Back
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How does the compressor lubrication system differ between a reciprocating and a centrifugal compressor?
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The oil pump for a reciprocating compressor is driven from the actual compressor shaft. The oil pump for a centrifugal compressor is driven by a seporate motor in a seporate oil sump in an effort to keep the oil and refrigerant seporate.
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True or False: Most reciprocating compressors have crankcase heaters.
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True
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True or False: All reciprocating compressors start up fully loaded.
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False
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Describe how a centrifugal compressor starts up at part load and then goes to full load.
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When the compressor starts up, the inlet guide vanes are closed to allow about a 15% refrigerant flow rate. When the motor reaches speed and the transition is made to the run winding the inlet guide vanes can be opened to what-ever load level the chiller needs.
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What system component must be started before the compressor in a chilled water system?
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Chilled water pump, condenser water pump, and the oil pump with a cetrifugal chiller.
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When condenser tubes become fouled, they may be cleaned by:
A. using a steel brush. B. using a brass brush. C. using a chisel and hammer. D. running a mixture of sand and water through them. |
B. using a brass brush.
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Describe what happens when an absorption chiller is operated when the cooling tower water is too cold.
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The salt inside can crystalize.
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The first step in starting a chilled water system is to:
A. determine that compressor unloading capabilities exist. B. establish that there is chilled water flow. C. determine that the blocked suction option is operating. |
B. establish that there is chilled water flow.
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A flow switch is:
A. typically a paddle placed in a water stream that moves with the water flow, operating a switch. B. a switch placed in an airstream that is activated by the airflow. C. A switch in the suction line of a chiller that is activated by the vapor refrigerant flow. |
A. typically a paddle placed in a water stream that moves with the water flow, operating a switch.
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A chiller field control circuit:
A. is often called an interlock circuit. B. is a circuit that starts systems one at a time, all of which must be started before the compressor starts. C. ensures that appropriate fans and pumps are started in the correct sequence. D. all of the above. |
D. all of the above.
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Which of the following compressors are considered positive displacement compressors?
A. scroll and rotary-screw. B. centrifugal. C. all of the above. |
A. scroll and rotary-screw.
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The reciprocating, scroll, and rotary-screw compressors:
A. have seporated external oil pumps. B. are lubricated from with in or have internal oil pump. |
B. are lubricated from with in or have internal oil pump.
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The rotary-screw chiller is:
A. air-cooled. B. water-cooled. C. either air- or water-cooled. |
C. either air- or water-cooled.
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Reciprocating chillers have crankcase heat to:
A. preheat the chiller water for better efficiency. B. prevent refrigerant migrating to the crankcase. C. preheat the compressor bearings for longer wear. D. minimize condenser subcooling. |
B. prevent refrigerant migrating to the crankcase.
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Water-cooled chillers must have water treatment to:
A. increase the pH content of the water. B. decrease the pH content of the water. C. prevent minerals and algae from forming. D. help preheat the water in the condenser circuit. |
C. prevent minerals and algae from forming.
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A megohmeter (megger) is used to check:
A. amperage to 100 amperes. B. amperage to 1,000 amperes. C. voltage to 10,000 volts. D. ohms to 1,000,000+ ohms. |
D. ohms to 1,000,000+ ohms.
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When a reciprocating compressor is sweating at the crankcase:
A. normal, good lubrication is taking place. B. it is flooding liquid back to the crankcase. C. there is too much superheat. D. the heat exchanger is working correctly. |
B. it is flooding liquid back to the crankcase.
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The instrument used to check for electrical grounds in a large motor is:
A. an ohmmeter. B. an ammeter. C. a thermistor. D. a megger (megohmmeter). |
D. a megger (megohmmeter).
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Tube failure can often be detected before the failure occurs using:
A. an ammeter. B. a megger. C. an eddy current testing instrument. D. pressure drop. |
C. an eddy current testinig instrument.
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Non-condensable gases are removed from an operating absorption chiller by means of:
A. a vacuum pump. B. a reciprocating compressor purge unit. C. a megger. D. an ohmmeter. |
B. a reciprocating compressor purge unit.
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