Term
57. What was the mian disadvantage of hand expansion valves in early refrigeration system?
a. they were big and bulky and took up a lot of space.
b. they always required service because they had many moving parts.
c. they did not automatically adjust to changing loads so an operator had to frequently check and adjust them.
d. the valve seat wore out very rapidly and would not hold when the valve was closed all the way. |
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Definition
| c. they did not automatically adjust to changing loads so an operator had to frequently check and adjust them 4-3 |
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Term
58. What is the advantage of a thermostatic expansion valve?
a. they will automatically adjust themselves to match varying load conditions
b. they create a fully wetted coil surface with coil capacity equal to a gravity flooded system
c. They can be used on g4ravity flooded, recirculated over-feed and DX systems
d. one size fits all evaporators. |
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Definition
| a. they will automatically adjust themselves to match varying load conditions 4-8 |
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Term
59. How many forces are involved in operating a thermostatic expansion valve?
a. one- only the bulb pressure.
b. two - only the bulb and spring pressure.
c. three - the bulb, spring and the evaporator pressure.
d. four- the bulb, spring, evaporator and atmospheric pressure |
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Definition
| c. three- the bulb, spring and the evaporator pressure. 4-1, 9 |
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Term
60. Which of the following b3est describes the term "flash gas"?
a. the vapor in the last 25% of travel in a DX coil
b. the gas that is discharged out of the compressor
c. the gas that is generated at the orifice of the expansion device
d. the gas that is traveling down the suction line toward the compressor. |
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Definition
| c. the gas that is generated at the orifice of the expansion device 4-5 |
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Term
61. What is the average starting point for setting superheat at the outlet of a DX coil?
a. 5F
b. 10F
c. 25F
d. 1F |
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Definition
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Term
62. Level adjustment of an "LL" type float switch assembly is accomplished by
a. adjusting the activation screw on the switch mechanism
b. repiping or re-attaching the float at a different level
c. recalibrating the switch height on the float assembly.
d. entering new level parameters in the float controller |
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Definition
| b. repiping or re-attaching the float at a different level 4-28 |
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Term
63. When services a DX air unit
a. it is acceptable to use the TXV as an isolation valve as the warm temp will result in a complete closing of the valve.
b. a separate isolation valve must always be used to isolate the coil.
c. the TXV can be used to isolate the coil if the superheat adjustment is turned completely in the "manual off" position
d. the TXV can be used to isolate the coil if the superheat adjustment is turned completely out to the "manual off" position. |
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Definition
| b. a separate isolation valve must always be used to isolate the coil. 4-12 |
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Term
64. Which of the following is a typical function of a low side vessel?
a. oil cooling
b. phase separation
c. thermo siphon refrigerant storage
d. subcooling liquid for low side use. |
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Definition
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Term
65. If a power element of a TXV lost its charge
a. the evaporator would starve
b. the evap would hunt
c. there would be low superheat at the coil outlet
d. the evap would flood |
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Definition
| a. the evap would starve 4-10 |
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Term
66. Hand expansion valves are
a. seldom used in new systems
b. only used to feed gravity flooded evaps
c. not used in series with another feed control device.
d. commonly used in series with another feed control device. |
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Definition
| d. commonly used in series with another feed control device 4-27 |
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Term
67. The thermostatic expansion valve is opened by forces coming from
a. evap pressure only
b. evap temp only
c. compressor pressure only
d. sensing bulb pressure |
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Definition
| d. sensing bulb pressure 4-10 |
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Term
68. A hand expansion valve can control the flow of refrigerant into an evap better than a typical stop valve because
a. It is larger than the liquid line pipe size feeding it.
b. it has a adjustable orifice designed to control flow.
c. it is made of special alloy steal that expands and contracts with temp change.
d. pointers can be attached to the hand wheel. |
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Definition
| b. it has an adjustable orifice designed to control flow 4-4 |
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Term
69. Where may hand expansion valves be found in modern industrial refrigeration system?
a. they are not used
b. they are commonly used as the only valve feeding the evaporator.
c. they are usually not used in series with another feed device.
d. they are commonly used in series with solenoid valves |
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Definition
| d. they are commonly used in series with solenoid valves 4-27 |
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Term
70. Which of the following forces does not work to control the flow rate through a thermostatic expansion valve.
a. bulb pressure
b. pump pressure
c. evap pressure
d. the superheat spring force |
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Definition
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Term
71. The function of a low side float valve is :
a. to maintain a constant liquid level in a vessel or evap to control the operation of a solenoid valve.
b. to control the operation of a solenoid valve.
c. to maintain the pressure in a vessel or evap at its desired operating level.
d. to help the hand expansion valve maintain the proper flow into a vessel or an evap |
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Definition
| a. to maintain a constant liquid level in a vessel or evap to control the operation of a solenoid valve. 4-30, 31 |
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Term
72. What forces work together to close a thermostatic expansion valve?
a. bulb pressure and superheat spring force
b. evap pressure and bulb pressure
c. the superheat spring force and refrigerant flow
d. evap pressure and superheat spring force |
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Definition
| d. evap pressure and superheat spring force. 4-9 |
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Term
73. Where may thermostatic expansion valves be found in modern industrial refrigeration system?
a. they are only used in small halocarbon systems.
b. they are commonly used on dry expansion evaps
c. they are commonly used on pumped overfeed evaps
d. they are commonly used in a bypass around an automatic liquid feed |
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Definition
| b. they are commonly used on dry expansion evaps. 4-8 |
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Term
74. The advantage of a float valve liquid make up device is:
a. 120vac control power
b. low cost
c. their design allows easy maintenance and or replacement
d. proportional responsiveness to changes in liquid level |
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Definition
| d. proportional responsiveness to changes in liquid level 4-31, 32 |
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Term
75. The float switch maintains the liquid level by
a. opening and closing the expansion valve.
b. opening and closing the liquid solenoid valve.
c. opening and closing the hot gas valve.
d. opening and closing the float valve. |
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Definition
| b. opening and closing the liquid solenoid valve 4-28 |
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Term
76. Heating the bulb of a Sporlan Level Master thermostatic expansion valve causes
a. increased liquid flow
b. increased superheat
c. decreased liquid flow
d. decreased bulb pressure |
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Definition
| a. increased liquid flow 4-33, 34 |
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Term
77. Why are hand expansion valves used in series with solenoid valves on a gravity flooded evaporator?
a. to protect the hand expansion valve from erosion damage.
b. Hand expansion valves are required to set evap pressure
c. to protect the solenoid valve from erosion damage
d. to reduce the operating pressure of the solenoid valve. 4-30 |
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Definition
| c. to protect the solenoid valve from erosion damage 4-30 |
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Term
78. Hand expansion valves are used in series with solenoid valves to
a. control evap pressure
b. regulate the flow of refrigerant
c. regulate the superheat generated in an evaporator
d. to protect the hand expansion valve from erosion damage |
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Definition
| b. regulate the flow of refrigerant 4-7 |
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