Compression Refrigeration System Pre-start Procedures Flashcards
The presence of non-condensable gases in the refrigeration system:
A) Reduces compressor capacity
B) Produces higher than normal high side pressure
C) Produces added stress on the compressor
D) All of the above
E) Reduces system efficiency
D) All of the above
Non-condensable gases tend to accumulate at the:
A) Low points in a refrigeration system
B) Highest point of the condenser
C) Lowest point of the evaporator
D) Elbows in the compressor discharge line
E) Valves in the compressor discharge line
B) Highest point of the condenser
A sulphur candle is a test for:
A) CFC leaks B) Freon leaks C) Vacuum seal D) Air leaks E) Ammonia leaks
E) Ammonia leaks
When pressure testing a new refrigeration system, which of the following gases are used?
A) Hydrogen B) Nitrogen C) Helium D) Oxygen E) Carbon monoxide
B) Nitrogen
Leak testing on a refrigeration system:
A) Is done with litmus paper for freon refrigerant
B) Is done with a sulphur stick for freon refrigerant
C) Is done with an electronic leak detector for HFC’s
D) Must be done with the compressor running
E) Is done with a vacuum in the system
C) Is done with an electronic leak detector for HFC’s
It is very important to slowly open oil drain valves and plugs in the crankcase for which of the following reasons?
A) The oil is very hot
B) The oil is very cold
C) Old oil is contaminated with refrigerant and may be very acidic
D) Oil can never be drained below the critical minimum level
E) Residual pressure in the crankcase may blow refrigerant vapour and oil out
E) Residual pressure in the crankcase may blow refrigerant vapour and oil out
When draining or replacing oil from a refrigeration compressor, it is important to:
A) Lock out the compressor motor or driver
B) Reduce crank case pressure to almost atmospheric
C) Shut down and isolate the compressor
D) All of the above
E) Exercise caution when removing drain plugs
D) All of the above
Combustion of HFC’s (halocarbon refrigerants) produces:
A) Phosgene gas B) Carbon Dioxide C) Chlorine gas D) Helium E) Water Vapour
A) Phosgene gas
To generate a vacuum in the crankcase of a refrigeration compressor the:
A) Discharge is throttled B) Suction is throttled C) Recirculation valve is throttled D) Crankcase vent is opened E) Bypass is cracked
B) Suction is throttled
Leaks in refrigeration systems that operate below atmospheric pressure:
A) Do not have to be identified before adding refrigerant
B) Do not impair performance
C) Result in a frequent need to add refrigerant
D) Result in frequent purge unit operation
E) Cause higher oil consumption
D) Result in frequent purge unit operation
Where on the system is the initial refrigerant charge given?
A) The evaporator B) The expansion valve C) The high side of the system D) The heat exchanger E) The low side of the system
C) The high side of the system
Which of the following is not a recommended step during the procedure for which dry nitrogen is used for a system leak test?
A) Open the cylinder shut-off valve and disconnect the nitrogen cylinder
B) Remove controls and relief valves that may be damaged by the test pressure
C) Set the pressure reducing valve for the minimum design pressure of the high side
D) Open the liquid line shut-off valve
E) Connect the nitrogen cylinder to the system charging valve
A) Open the cylinder shut-off valve and disconnect the nitrogen cylinder
Which of the following statements about adding oil to a system is true?
A) None of the above
B) Oil cannot be added while the compressor is in operation
C) Oil is added by charging it into the crankcase
D) The system must be recharged, purged and re-pressurised after the oil has been added
E) Since the crankcase is pressurised it is not possible for air to get in the system when adding oil
C) Oil is added by charging it into the crankcase
Often adding oil to refrigeration compressors:
A) Is done when the compressor discharge valve is closed
B) Is done with the charging line open
C) Is done with a vacuum in the crankcase
D) Requires preheated oil
E) Is done with the equalizing valve closed
C) Is done with a vacuum in the crankcase
Non-condensable gases are removed by the:
A) Purge System B) Collection tank C) Condenser sump D) Evaporators E) Oil filters
A) Purge System
