Book 2 Chapter 26: Refrigeration & AC System Controls

Question 1

Why must you avoid running a refrigeration system below 14kPa when pumping down?
A) A slightly positive system pressure is required to prevent air infiltration
B) Too much refrigerant will be required for a recharge
C) The compressor will need to be stopped to prevent it running dry
D) The system heat exchangers will ice up

Answer 1

A) A slightly positive system pressure is required to prevent air filtration

Question 2

What is the purpose of the chilled water flow switch?
A) Starts the compressor on a low refrigerant flow condition
B) Opens the vanes so that the compressor can be restarted under load
C) Protects the chiller from freezing due to lack of water flow
D) Starts the chilled water booster pump

Answer 2

C) Protects the chiller from freezing due to lack of water flow

Question 3

Where can refrigeration system log sheets be obtained from?
A) Refrigeration system manufacturers
B) Inspection and insurance companies
C) Developed by the refrigeration system operator
D) All of the above

Answer 3

D) All of the above

Question 4

Which of the following is not a benefit of a preventive maintenance program?
A) Control of labour and material costs
B) Allows for the accumulation of all spare parts for each piece of equipment in case of a major breakdown
C) Accumulation of history records for each piece of equipment
D) Better means of identifying causes of breakdowns

Answer 4

B) Allows for the accumulation of all spare parts for each piece of equipment in case of a major breakdown

Question 5

What is the symptom of a refrigeration system that has high suction pressure due to an oversized expansion valve?
A) An abnormally cold suction line
B) Undersized compressor
C) Fouled condenser
D) Contaminants in the refrigerant

Answer 5

A) An abnormally cold suction line

Question 6

The safety control on a centrifugal compressor that ensures the compressor will only be started under a no-load condition is called what?
A) Low oil pressure cutout switch
B) Motor demand limiter
C) Vane closed switch
D) Chilled water flow switch
E) Condenser high pressure cutout

Answer 6

C) Vane closed switch

Question 7

Which of the following code books deals with refrigeration systems?
A) CSA B52
B) CSA B51
C) ASME Section VII
D) ASNI
E) ASME Section IV

Answer 7

A) CSA B52

Question 8

Before starting a compression refrigeration system:
A) Ensure that compressor oil level and temperature is within specification
B) Open the condenser fan breakers
C) Make sure recycle timer is engaged
D) Shut off engine room fans
E) Close louvres to engine room air make up units

Answer 8

A) Ensure that compressor oil level and temperature is within specification

Question 9

Which of the following steps is not part of the start-up procedure of centrifugal compressor refrigerating system?
A) Operate the oil pump for at least 10 minutes before starting the compressor
B) Open the main circuit breakers
C) Open the makeup water valve
D) Open the stop valves in the chilled water system
E) Check the refrigerant levels

Answer 9

B) Open the main circuit breakers

Question 10

Refrigeration systems:
A) Require operators to be familiar with the system
B) Do not require supervision
C) Start automatically and need no operator input
D) Will shutdown automatically if there is a problem
E) Are standard and operated in similar ways

Answer 10

A) Require operators to be familiar with the system

Question 11

When some refrigeration systems are to be shutdown for a prolonged period of time they should be “pumped down” and the refrigerant stored in the:
A) Accumulator
B) Compressor
C) Receiver
D) Evaporator
E) Supply cylinders

Answer 11

C) Receiver

Question 12

When starting a compression refrigeration system after ensuring that all components and auxiliaries are properly energized:
A) Check the pressure cutouts and interlocks
B) Open the suction
C) Shut the king valve
D) Push the start button
E) Close the water supply to the condenser

Answer 12

A) Check the pressure cutouts and interlocks

Question 13

Before starting a compression refrigeration system:
A) Close the expansion valves
B) Close the compressor discharge
C) Bleed the discharge check valve
D) Close the king valve
E) Check compressor oil

Answer 13

E) Check compressor oil

Question 14

If the compressor suction pressure is too high it may be due to:
A) Expansion valve is struck open
B) Broken compressor suction valves
C) Too much load on the evaporator
D) All of the above
E) None of the above

Answer 14

D) All of the above

Question 15

A system of regularly scheduled inspections and lubrications along with the adjustments, minor parts replacement and minor repairs necessary to keep the refrigerating plant and equipment in good operating condition is defined as what:
A) Routine operation
B) Safety controls
C) Regular maintenance
D) Preventative maintenance
E) None of the above

Answer 15

D) Preventative maintenance

Question 16

What is the symptom of a refrigeration system when the compressor suction pressure is too low due to an obstructed expansion valve?
A) Evaporator dirty or iced up
B) Conditioned space too cold
C) Compressor short-cycles
D) Lack of refrigerant
E) Loss of capacity

Answer 16

E) Loss of capacity

Question 17

What is the symptom of a refrigeration system when the system is short of capacity due to a clogged strainer?
A) Expansion valve stuck
B) There is a temperature difference in liquid line before and after strainer
C) Flash gas in liquid line
D) Superheat too high
E) Expansion valve hisses

Answer 17

B) There is a temperature difference in liquid line before and after strainer

Question 18

On smaller capacity refrigeration compressors the _______ valves prior to starting.
A) Close the suction and open the discharge
B) Close the suction and discharge
C) Open the suction and close the discharge
D) Open the suction and discharge
E) Open the bypass

Answer 18

D) Open the suction and discharge

Question 19

The information card that code requires for refrigeration systems over 125kW must include all of the following information except:
A) Instructions for shutting down the system in case of emergency
B) The name,address, and telephone number of the regulatory authority
C) Instructions to notify said authority immediately in case of emergency
D) Instructions for starting up the system in case of emergency
E) The name, address and day and night telephone numbers for obtaining service

Answer 19

D) Instructions for starting up the system in case of emergency

Question 20

The low oil pressure cutout switch is a safety shutdown device that prevents compressor operation when oil pressure is:
A) Too high
B) Too cold
C) Below a safe minimum value
D) Below the refrigerant level
E) Too low in the crankcase

Answer 20

C) Below a safe minimum value

Question 21

What is the symptom of a refrigeration system when the compressor or system is noisy due to a dry or scored seal?
A) Coupling bolts loose
B) Internal parts loose
C) Lack of oil
D) Coupling misaligned
E) The compressor seat is squeaky during operation

Answer 21

E) The compressor seat is squeaky during operation

Question 22

What is the symptom of a refrigeration system when the compressor “short-cycles” due to the low pressure controller differential set too close?
A) Reduced air flow due to dirty air filters
B) Intermittent contact in electrical circuit
C) Leaky liquid line solenoid valve
D) Compressor operates normally but starts and stops frequently
E) Reduced air flow due to broken fan belt

Answer 22

D) Compressor operates normally but starts and stops frequently

Question 23

The valve closed switch is in the motor starting circuit so that the compressor can only be started when the vanes are in the _______ position.
A) Closed position
B) Compressor closed
C) Evaporator open
D) Evaporator closed
E) Compressor open

Answer 23

A) Closed position

Question 24

The benefits of a good preventative maintenance program may include all of the following except:
A) Better means of identifying causes of breakdowns
B) Reduced life expectancy of plant and equipment
C) Control of labour and material cost
D) Accumulation of history records for each piece of equipment
E) Reduced spare parts inventory required

Answer 24

B) Reduced life expectancy of plant and equipment

Question 25

A clause in a code of the authority having jurisdiction states “It shall be the duty of the person in charge of the premises on which a refrigerating system with prime mover(s) having a capacity in excess of _________ is installed to place conspicuously and as near as practicable to the refrigerant compressor a card giving directions for the operation of the system, including precautions to be observed in case of breakdown or leak as follows.”
A) 500kW
B) 100kW
C) 250kW
D) 125kW
E) 25kW

Answer 25

D) 125kW