Book 2 Chapter 25: Compressor Refrigeration System Pre-Startup Procedures

Question 1

Why should oxygen not be used to pressurize a system for leak checking purposes?
A) It could result in explosion
B) The oxygen can cause pitting of the parts of the system
C) An external source of moisture free oxygen is required
D) The oxygen combines with any non-condensable gases present to increase the system head pressure

Answer 1

A) It could result in an explosion

Question 2

After a refrigeration system is installed, a positive pressure testis performed using:
A) Propane
B) Methane
C) Nitrogen
D) Oxygen

Answer 2

C) Nitrogen

Question 3

What personal protective equipment (PPE) is required when charging a system with refrigerant?
A) Goggles
B) Face shield
C) Rubber gloves
D) Encapsulated suit

Answer 3

C) Rubber gloves

Question 4

What are some of the non-condensable gases that can be found in a refrigeration system?
A) Air
B) Impurities in the refrigerant
C) Gases caused by lubrication breakdown
D) All of the above

Answer 4

D) All of the above

Question 5

When it’s required to add oil to an operating refrigeration compressor and an oil pump is unavailable, what alternate method can be used to add oil?
A) Throttle the suction and feed oil to the crankcase
B) Throttle the discharge and feed oil into the suction line
C) Throttle the suction and feed oil into the suction line
D) Throttle the discharge and feed oil into the crankcase

Answer 5

A) Throttle the suction and feed oil to the crankcase

Question 6

The presence of non-condensate gases in the refrigeration system:
A) Produces higher than normal high side pressure
B) Reduces compressor capacity
C) Reduces system efficiency
D) Produces added stress on the compressor
E) All of the above

Answer 6

E) All of the above

Question 7

Non-condensable gases tend to accumulate at the:
A) Valves in the compressor discharge line
B) Elbows in the compressor discharge line
C) Low points in a refrigeration system
D) Highest point of the condenser
E) Lowest point of the evaporator

Answer 7

D) Highest point of the condenser

Question 8

A sulphur candle is a test for:
A) Ammonia leaks
B) Air leaks
C) Vacuum seal
D) CFC leaks
E) Freon leaks

Answer 8

A) Ammonia leaks

Question 9

When pressure testing a new refrigeration system, which of the following gases are used?
A) Oxygen
B) Helium
C) Nitrogen
D) Carbon monoxide
E) Hydrogen

Answer 9

C) Nitrogen

Question 10

Leak testing on a refrigeration system:
A) Is done with a vacuum in the system
B) Is done with litmus paper for Freon refrigerant
C) Is done with a sulphur stick for Freon refrigerant
D) Must be done with the compressor running
E) Is done with an electronic leak detector for HFC’s

Answer 10

E) Is done with an electronic leak detector for HFC’s

Question 11

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 cold
B) Residual pressure in the crankcase may blow refrigerant vapour and oil out
C) Oil can never be drained below the critical minimum level
D) Old oil is contaminated with refrigerant and may be very acidic
E) The oil is very hot

Answer 11

B) Residual pressure in the crankcase may blow refrigerant vapour and oil out

Question 12

When draining or replacing oil from a refrigeration compressor, it is important to:
A) Lock out the compressor motor or driver
B) Exercise caution when removing drain plugs
C) Reduce crankcase pressure to almost atmospheric
D) Shut down and isolate the compressor
E) All of the above

Answer 12

E) All of the above

Question 13

Combustion of HFC’s (halocarbon refrigerants) produces:
A) Chlorine gas
B) Carbon dioxide
C) Water vapour
D) Helium
E) Phosgene gas

Answer 13

E) Phosgene gas

Question 14

To generate a vacuum in the crankcase of a refrigeration compressor the:
A) Discharge is throttled
B) Recirculation valve is throttled
C) Bypass is cracked
D) Crankcase vent is opened
E) Suction is throttled

Answer 14

E) Suction is throttled

Question 15

Leaks in the refrigeration systems that operate below atmospheric pressure:
A) Result in frequent purge unit operation
B) Result in a frequent need to add refrigerant
C) Do not have to be identified before adding refrigerant
D) Do not impair performance
E) Cause higher oil consumption

Answer 15

A) Result in frequent purge unit operation

Question 16

Where on the system is the initial refrigerant charge given?
A) The expansion valve
B) The low side of the system
C) The high side of the system
D) The heat exchanger
E) The evaporator

Answer 16

C) The high side of the system

Question 17

Which of the following is not a recommended step during the procedure for which dry nitrogen is used for a system leak test?
A) Set the pressure reducing valve for the minimum design pressure of the high side
B) Connect the nitrogen cylinder to the system charging valve
C) Remove controls and relief valves that may be damaged by the test pressure
D) Open the liquid line shut-off valve
E) Open the cylinder shut-off valve and disconnect the nitrogen cylinder

Answer 17

E) Open the cylinder shut-off valve and disconnect the nitrogen cylinder

Question 18

Which of the following statements about adding oil to a system is true?
A) Oil is added by charging it into the crankcase
B) Oil cannot be added while the compressor is in operation
C) Since the crankcase is pressurized it is not possible for air to get in the system when adding oil
D) The system must be recharged, purged and re-pressurized after the oil has been added
E) None of the above

Answer 18

A) Oil is added by charging it into the crankcase

Question 19

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

Answer 19

C) Is done with a vacuum in the crankcase

Question 20

Non-condensable gases are removed by the:
A) Collection tank
B) Oil filters
C) Evaporators
D) Purge system
E) Condenser sump

Answer 20

D) Purge system

Question 21

In a process called “copper plating” the acids remove copper from heat exchanger surfaces and redeposit it at points of:
A) High flow
B) Low temperature
C) High pressure
D) High temperature
E) Low pressure

Answer 21

D) High temperature

Question 22

The pressurizing gas is admitted to the refrigeration system through the _______ valve.
A) Queen
B) Drain
C) Charging
D) King
E) Isolation

Answer 22

C) Charging

Question 23

Evacuation of the refrigeration system should not be attempted unless the temperature of the surrounding air is ________ or higher.
A) 15ºC (59ºF)
B) 10ºC (50ºF)
C) 5ºC (41ºF)
D) 0ºC (32ºF)
E) 20ºC (68ºF)

Answer 23

E) 20ºC (68ºF)

Question 24

Overcharging a system causes _____________ creating high compressor power consumption.
A) High condenser pressure
B) High compressor suction and discharge pressures
C) Low suction evaporator pressure
D) High receiver temperature
E) Low evaporator temperature

Answer 24

B) High compressor suction and discharge pressures

Question 25

During the charging process the refrigerant that passes through the system is stored in liquid form in the:
A) Chiller
B) Compressor
C) Receiver
D) Evaporator
E) Expansion valve

Answer 25

C) Receiver

Question 26

Positive pressure testing of a refrigeration system is done using dry ___________ gas as the pressure agent.
A) Oxygen
B) Nitrogen
C) Hydrogen sulphide
D) Helium
E) Carbon monoxide

Answer 26

B) Nitrogen

Question 27

Non-condensable gases in a refrigeration system consist mainly of _______ that may have leaked into the system by improper operating or maintenance procedures.
A) Impurities in the refrigerant
B) Sulphur dioxide
C) Air
D) Nitrogen oxide
E) Gases caused by lubrication breakdown

Answer 27

C) Air

Question 28

It is the ________ part of the refrigerant molecular composition that during combustion causes the green flame of the halide detector.
A) Chlorine
B) Fluorine
C) Carbon
D) Hydrogen
E) Iodine

Answer 28

A) Chlorine

Question 29

Oil is added to the refrigeration system by _________ while the compressor is in operation.
A) Pouring it into the condenser
B) Pouring it into the crankcase
C) Charging it into the evaporator with a suitable pump
D) Charging it into the condenser with a suitable pump
E) Charging it into the crankcase with a suitable pump

Answer 29

E) Charging it into the crankcase with a suitable pump

Question 30

Regulations of the authority having jurisdiction may require that a ________ be reported.
A) Loss of refrigerant
B) Change of the compressor
C) Flush of the condenser
D) Evacuation of the evaporator
E) Loss of cooling water

Answer 30

A) Loss of refrigerant