Book 2: Unit 5 - Review: (23 - 26) Flashcards
The high oil temperature cutout is a safety control that shuts down the compressor when the lubricating oil temperature becomes too high due to:
Select one:
A. Condenser high temperature
B. Evaporator high temperature
C. Condenser high pressure
D. Loss of refrigerant
E. Loss of oil cooling
E. Loss of oil cooling
The operation of the compressor (starting, stopping, and unloading) may be accomplished by a _____ type of actuated control.
Select one:
A. Density
B. Humidity
C. Mass
D. Volume
E. Level
B. Humidity
The most common application of evaporator capacity control is to use:
Select one:
A. Sectional evaporators
B. Sectional receivers
C. Variable evaporators
D. Adjustable evaporators
E. Sectional condensers
A. Sectional evaporators
The thermostatic expansion valve must admit enough liquid to maintain the superheat at the evaporator outlet at _____ to provide for maximum evaporator efficiency.
Select one:
A. 5°C to 6°C (41°F to 43°F)
B. 10°C to 11°C (50°F to 52°F)
C. 2°C to 3°C (36°F to 38°F)
D. 8°C to 9°C (46°F to 48°F)
E. 0°C to 1°C (32°F to 34°F)
A. 5°C to 6°C (41°F to 43°F)
The pressure-actuated refrigeration control is actuated by the:
Select one:
A. Suction pressure of the condenser
B. Discharge pressure of the compressor
C. Suction temperature of the compressor
D. Suction pressure of the compressor
E. Discharge pressure of the receiver
D. Suction pressure of the compressor
What is the purpose of the “weighted valve pin” used with a high-pressure float valve?
Select one:
A. Control the pressure in the refrigeration system
B. Control the flow of refrigerant into the condenser
C. Control the flow of refrigerant into the evaporator
D. Maintain a back pressure in the condenser
E. Reduce the amount of line frosting after the float valve
E. Reduce the amount of line frosting after the float valve
Caution when burned the halocarbon refrigerants containing fluorine produce a very toxic _____ gas.
Select one:
A. Phosgene
B. Sulphur dioxide
C. Hydrogen sulphide
D. Mustard
E. Carbon monoxide
A. Phosgene
In a process called “copper plating” the acids remove copper from heat exchanger surfaces and redeposit it at points of:
Select one:
A. Low pressure
B. Low temperature
C. High temperature
D. High pressure
E. High flow
C. High temperature
In the event of a low oil pressure condition, the oil pressure failure switch will:
Select one:
A. Open the recycle valve to take the load off the compressor
B. Shutdown the compressor
C. Stop the air circulation fan
D. Stop the flow of refrigerant to the system
E. Sound an audible alarm
B. Shutdown the compressor
Motor overload protection is a manual reset device that will take the motor itself offline when the current drawn by the motor exceeds:
Select one:
A. Its maximum allowable oil temperature
B. Its minimum allowable value
C. The evaporator maximum allowable temperature
D. The condenser maximum allowable pressure
E. Its maximum allowable value
E. Its maximum allowable value
The force that tends to open the thermal expansion valve is the force exerted by the:
Select one:
A. Pressure in the condenser
B. Compressor outlet pressure
C. Spring
D. Pressure in the evaporator
E. Thermal element
E. Thermal element
What is the symptom of a refrigeration system that has high suction pressure due to an oversized expansion valve?
Select one:
A. Fouled condenser
B. Contaminants in the refrigerant
C. An abnormally cold suction line
D. Non-condensables in the system
E. Undersized compressor
C. An abnormally cold suction line
All of the following methods are used to control the refrigeration compressor output except:
Select one:
A. Cylinder unloaders
B. Cylinder bypass
C. Hot gas bypass
D. Intermittent operation
E. High-pressure float
E. High-pressure float
Ammonia leaks in refrigeration systems can also be detected by using a sulphur candle which, when lit, gives off a cloud of _____ smoke when exposed to ammonia fumes or vapour.
Select one:
A. Bright green
B. Orange
C. Light blue
D. White
E. Reddish hue
D. White
The low oil pressure cutout switch is a safety shutdown device that prevents compressor operation when oil pressure is:
Select one:
A. Too high
B. Below a safe minimum value
C. Below the refrigerant level
D. Too cold
E. Too low in the crankcase
B. Below a safe minimum value
One of the safety devices on a centrifugal refrigeration compressor that acts preventing the compressor from being started is the _____ switch.
Select one:
A. Vane closed
B. Evaporator temperature high
C. Condenser temperature low
D. Refrigerant level low
E. Refrigerant level high
A. Vane closed
The operation of the compressor (starting, stopping, and unloading) is usually accomplished by a _____ type of actuated control.
Select one:
A. Density
B. Temperature
C. Mass
D. Level
E. Volume
B. Temperature
What is the purpose of the chilled water flow switch?
Select one:
A. Starts the chilled water booster pump
B. It confirms refrigerant flow to the evaporator
C. Starts the compressor on a low refrigerant flow condition
D. Protects the chiller from freezing due to lack of water flow
E. Opens the vanes so that the compressor can be restarted under load
D. Protects the chiller from freezing due to lack of water flow
One of the most important secondary controls in a refrigerating system is the refrigerant flow control used to regulate the amount of liquid refrigerant flowing into the:
Select one:
A. Evaporator
B. Refrigerated space
C. Refrigerator
D. Condenser
E. Receiver
A. Evaporator
All of the following methods are used to control the refrigeration compressor output except:
Select one:
A. Intermittent operation
B. Variable inlet guide vanes
C. Thermodynamic expansion valve
D. Cylinder Unloaders
E. Speed control
C. Thermodynamic expansion valve
All of the following methods are used to control the refrigeration compressor output except:
Select one:
A. Intermittent operation
B. Variable inlet guide vanes
C. Thermodynamic expansion valve
D. Cylinder Unloaders
E. Speed control
C. Thermodynamic expansion valve
Oil is added to the refrigeration system by _____ while the compressor is in operation.
Select one:
A. Charging it into the evaporator with a suitable pump
B. Pouring it into the crankcase
C. Charging it into the crankcase with a suitable pump
D. Charging it into the condenser with a suitable pump
E. Pouring it into the condenser
C. Charging it into the crankcase with a suitable pump
The cylinder bypass method of refrigeration compressor capacity control requires returning high-temperature vapour back to the compressor inlet this hot vapor must be tempered by using the _____ expansion valve to mix a low-temperature saturated mixture of refrigerant with the compressor discharge vapor.
Select one:
A. De-superheating
B. Capillary
C. Automatic
D. Hand
E. Thermodynamic
A. De-superheating
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. Water
B. Air
C. Refrigerant
D. Oil
E. Carbon dioxide
C. Refrigerant
The high-pressure safety cutout protects the refrigerating system from higher than normal pressures due to the:
Select one:
A. High compressor oil pressure
B. Presence of non-condensables in evaporator
C. Presence of refrigerants in the system
D. Loss of refrigerant
E. Presence of non-condensables in the system
E. Presence of non-condensables in the system
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 open
C. Compressor open
D. Evaporator closed
E. Closed position
E. Closed position
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. 0°C – 0.5°C (32°F - 33°F)
B. 2.5°C - 3°C (36.5°F – 37.5°F)
C. 1.5°C - 2°C (35°F – 35.5°F)
D. 2°C – 2.5°C (35.5°F – 36.5°F)
E. 1°C – 1.5°C (34°F - 35°F)
B. 2.5°C - 3°C (36.5°F – 37.5°F)
To compensate for a large pressure drop in an evaporator, the thermal expansion valve is equipped with an equalizing line which connects the underside of the diaphragm or bellows with the:
Select one:
A. Inlet of the evaporator instead of the outlet
B. Outlet of the condenser instead of the inlet
C. Outlet of the receiver instead of the inlet
D. Outlet of the evaporator instead of the inlet
E. Inlet of the condenser instead of the outlet
D. Outlet of the evaporator instead of the inlet
The thermostatic refrigeration controller has a differential adjustment that sets the temperature at which the:
Select one:
A. Level in the evaporator control activates
B. Fan starts and stops
C. Cut-in and cut-out occurs
D. Expansion valve opens and closes
E. Condenser cooling water control activates
C. Cut-in and cut-out occurs
What is the symptom of a refrigeration system when the compressor runs continuously due to a lack of refrigerant?
Select one:
A. Bubbles in the sight glass
B. Excessive load
C. Thermostat set too low
D. Low temperature of substance to be cooled
E. High discharge pressure
A. Bubbles in the sight glass
The automatic expansion valve is a liquid refrigerant control valve that maintains a constant _____ during the time the compressor is operating, regardless of load.
Select one:
A. Condenser pressure
B. Compressor discharge pressure
C. Condenser temperature
D. Evaporator temperature
E. Evaporator pressure
E. Evaporator pressure
What is the symptom of a refrigeration system when the compressor “short-cycles” due to the low pressure controller differential set too close?
Select one:
A. Reduced air flow due to broken fan belt
B. Reduced air flow due to dirty air filters
C. Intermittent contact in electrical circuit
D. Compressor operates normally but starts and stops frequently
E. Leaky liquid line solenoid valve
D. Compressor operates normally but starts and stops frequently
The high motor temperature cutout stops the compressor if there is a loss of motor cooling or a motor overload due to malfunction of the:
Select one:
A. High-pressure safety cutout
B. High oil temperature cutout
C. Condenser cooling water regulating valve
D. Operating controls
E. Low limit thermostat
D. Operating controls
The bimetal element thermostat produces mechanical when subjected to _____ changes.
Select one:
A. Electrical
B. Electronic
C. Pressure
D. Temperature
E. Humidity
D. Temperature
What is the symptom of a refrigeration system when the system is short of capacity due to a clogged strainer?
Select one:
A. There is a temperature difference in liquid line before and after strainer
B. Flash gas in liquid line
C. Expansion valve stuck
D. Expansion valve hisses
E. Superheat too high
A. There is a temperature difference in liquid line before and after strainer
During charging of the refrigeration system short cycling of the compressor should be avoided due to the starting stress which is placed on the:
Select one:
A. Expansion valve
B. Evaporator level control
C. Compressor motor
D. Condenser cooling water valve
E. Compressor valves
C. Compressor motor
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. 125 kW
B. 500 kW
C. 250 kW
D. 100 kW
E. 25 kW
A. 125 kW
What is the symptom of a refrigeration system when the compressor fails to start due to an open control circuit?
Select one:
A. Full line voltage at terminals
B. Seized compressor
C. Power on motor terminals
D. No power on terminals of starter holding coil
E. Circuit breaker closed
D. No power on terminals of starter holding coil
The _____ is used in those systems where a drop in temperature below the minimum setting of the operating thermostat could result in damage to the equipment.
Select one:
A. Pressure-operated safety switch
B. Solenoid valve
C. Evaporator pressure regulator
D. Low limit thermostat
E. Pressure limiting device
D. Low limit thermostat
The thermostatic refrigeration controller has a range adjustment that sets the temperature level at which the:
Select one:
A. Condenser cooling water control activates
B. Expansion valve opens and closes
C. Fan starts and stops
D. Level in the evaporator control activates
E. Cut-in and cut-out occurs
E. Cut-in and cut-out occurs
