chapter 26 Flashcards
(29 cards)
What is the symptom of a refrigeration system when the system is short of capacity due to a clogged strainer?
Select one:
A.
Flash gas in liquid line
B.
Expansion valve hisses
C.
There is a temperature difference in liquid line before and after strainer
D.
Superheat too high
E.
Expansion valve stuck
C.
There is a temperature difference in liquid line before and after strainer
The purging unit of the refrigeration system should be operated for at least _____ minutes before the compressor is started (time depends on the size of the system).
Select one:
A.
5
B.
20
C.
10
D.
25
E.
15
C.
10
What is the symptom of a refrigeration system when the compressor discharge pressure is too high due to the improper operation of the evaporative condenser?
Select one:
A.
Overcharge of refrigerant
B.
Very hot condenser
C.
Fouled tubes in shell and tube condenser
D.
Scaled coil surface
E.
Non-condensables in system
D.
Scaled coil surface
refrigeration system log sheets can be obtained from all of the following except:
Select one:
A.
Refrigeration system manufacturers
B.
Government agencies
C.
Inspection companies
D.
Developed by the refrigeration system operator
E.
Insurance companies
B.
Government agencies
If the refrigeration compressor is equipped with an oil sump heater, ensure it is energized and that the oil temperature is high enough to drive off any:
Select one:
A.
Carbon dioxide
B.
Air
C.
Refrigerant
D.
Oil
E.
Water
C.
Refrigerant
When a refrigeration system is to be down for a prolonged period of time, it should be “pumped down” and all refrigerant stored in the:
Select one:
A.
Accumulator
B.
Condenser
C.
Compressor
D.
Receiver
E.
Evaporator
D.
Receiver
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:”
Select one:
A.
500 kW
B.
250 kW
C.
25 kW
D.
100 kW
E.
125 kW
E.
125 kW
What is the symptom of a refrigeration system when the compressor suction pressure is too low due an obstructed expansion valve?
Select one:
A.
Lack of refrigerant
B.
Conditioned space too cold
C.
Loss of capacity
D.
Evaporator dirty or iced up
E.
Compressor short-cycles
C.
Loss of capacity
What is the purpose of the chilled water flow switch?
Select one:
A.
Starts the compressor on a low refrigerant flow condition
B.
It confirms refrigerant flow to the evaporator
C.
Opens the vanes so that the compressor can be restarted under load
D.
Starts the chilled water booster pump
E.
Protects the chiller from freezing due to lack of water flow
E.
Protects the chiller from freezing due to lack of water flow
What is the symptom of a refrigeration system when the compressor runs continuously due to a lack of refrigerant?
Select one:
A.
High discharge pressure
B.
Excessive load
C.
Bubbles in the sight glass
D.
Thermostat set too low
E.
Low temperature of substance to be cooled
C.
Bubbles in the sight glass
The “king” valve is located on the refrigerant:
Select one:
A.
Evaporator outlet
B.
Condenser inlet
C.
Receiver inlet
D.
Receiver outlet
E.
Compressor inlet
D.
Receiver outlet
What is the symptom of a refrigeration system when the compressor fails to start due to an open control circuit?
Select one:
A.
No power on terminals of starter holding coil
B.
Circuit breaker closed
C.
Seized compressor
D.
Full line voltage at terminals
E.
Power on motor terminals
A.
No power on terminals of starter holding coil
The low oil pressure cutout switch is a safety shutdown device that prevents compressor operation when oil pressure is:
Select one:
A.
Too cold
B.
Below the refrigerant level
C.
Below a safe minimum value
D.
Too high
E.
Too low in the crankcase
C.
Below a safe minimum value
The information card that code requires for refrigeration systems over 125 kW must include all of the following information except:
Select one:
A.
The name, address and day and night telephone numbers for obtaining service
B.
Instructions to notify said authority immediately in case of emergency
C.
Instructions for starting up the system in case of emergency
D.
The name, address, and telephone number of the regulatory authority
E.
Instructions for shutting down the system in case of emergency
C.
Instructions for starting up the system in case of emergency
The benefits of a good preventative maintenance program may included all of the following except:
Select one:
A.
Accumulation of history records for each piece of equipment
B.
Better means of identifying causes of breakdowns
C.
Reduced life expectancy of plant and equipment
D.
Control of labour and material cost
E.
Reduced spare parts inventory required
C.
Reduced life expectancy of plant and equipment
The vane closed switch is in the motor starting circuit so that the compressor can only be started when the vanes are in the _____ position.
Select one:
A.
Compressor closed
B.
Evaporator closed
C.
Compressor open
D.
Evaporator open
E.
Closed position
E.
Closed position
On smaller capacity refrigeration compressors the _____ valves prior to starting.
Select one:
A.
Close the suction and discharge
B.
Close the suction and open the discharge
C.
Open the suction and close the discharge
D.
Open the bypass
E.
Open the suction and discharge
E.
Open the suction and discharge
The refrigerant low temperature cutout is a safety low limit thermostat that senses the:
Select one:
A.
Water temperature in the evaporator
B.
Refrigerant temperature in the condenser
C.
Refrigerant pressure in the chiller
D.
Refrigerant temperature in the chiller
E.
Water temperature in the chiller
D.
Refrigerant temperature in the chiller
What is the symptom of a refrigeration system that has high suction pressure due to an oversized expansion valve?
Select one:
A.
Contaminants in the refrigerant
B.
Non-condensables in the system
C.
An abnormally cold suction line
D.
Undersized compressor
E.
Fouled condenser
C.
An abnormally cold suction line
Most refrigeration systems are controlled by a motor demand limiter that limits the:
Select one:
A.
Maximum refrigerant flow to the compressor
B.
Maximum water flow to the condenser
C.
Minimum current flow to the compressor motor
D.
Minimum refrigerant flow to the evaporator
E.
Maximum current flow to the compressor motor
E.
Maximum current flow to the compressor motor
The condenser high pressure cutout is a high limit switch that is generally activated by:
Select one:
A.
Low condenser pressure
B.
High compressor discharge temperature
C.
High evaporator temperature
D.
Inadequate condenser cooling
E.
An overloaded evaporator
D.
Inadequate condenser cooling
What is the symptom of a refrigeration system when the compressor or system is noisy due to a dry or scored seal?
Select one:
A.
The compressor seal is squeaky during operation
B.
Internal parts loose
C.
Coupling bolts loose
D.
Lack of oil
E.
Coupling misaligned
A.
The compressor seal is squeaky during operation
On larger capacity refrigeration compressors the _____ valves prior to starting.
Select one:
A.
Close the suction and discharge
B.
Close the suction and open the discharge
C.
Open the suction and close the discharge
D.
Open the suction and discharge
E.
Open the bypass
B.
Close the suction and open the discharge
The chilled water temperature switch will shut down the compressor if the temperature of the water leaving the chiller drops to approximately:
Select one:
A.
2°C – 2.5°C (35.5°F – 36.5°F)
B.
2.5°C - 3°C (36.5°F – 37.5°F)
C.
0°C – 0.5°C (32°F - 33°F)
D.
1.5°C - 2°C (35°F – 35.5°F)
E.
1°C – 1.5°C (34°F - 35°F)
B.
2.5°C - 3°C (36.5°F – 37.5°F)
