WorksheetsSTAR EXAM 3
Total questions: 25
Worksheet time: 13mins
51. On a typically evaporator employing a TXV the liquid refrigerant should be completely boiled to a vapor?
near the evaporator outlet
approximately halfway through the evaporator
near the evaporator inlet
between the compressor and the evaporator
52. What type of TXV would be best for an application that was exposed to fluctuating ambient temperatures?
balanced port TXVs
internally equalized TXV
pressure limiting TXV
self equalizing TXV
53. Pressure-limiting TXV’s are generally applied on systems when
the compressor will operate at low temperatures
it is necessary to shut off the condenser fan during a hot pull down
there are constant evaporator loads
it is necessary to shut off the refrigerant flow to the evaporator
when the suction pressure reaches a predetermined pressure
54. Which of the following is not true regarding the evaporator in a refrigeration system?
it rejects heat from the conditioned space
it absorbs heat from the conditioned space
it removes moisture from the air stream
it allows for the latent heat of vaporization in a system
55. Heat that is added to the refrigerant stream after the 100% saturated vapor point is called?
latent heat
artificial heat
extended heat
superheat
56. Multiple refrigerant circuits are preferred on evaporators that are?
stainless steel tubed
copper tubed
small or short
large or long
57. In a system where the evaporator temperature operators above 32º F the technician needs to be concerned with?
methods of defrosting the coil
adding refrigerant
increasing the rate of vaporization
none of the above
58. The fin spacing per inch on a medium-temperature evaporator is
the same on a low-temperature evaporator
closer together than on low-temperature evaporator
farther apart than on low-temperature evaporators
the same on high-temperature evaporators
59. A refrigeration system that utilizes two or three stages of low temperature refrigeration
uses flowing water to provide refrigeration
is called a cascade refrigeration system
provides medium temperature refrigeration
provides high temperature refrigeration
60. When leak testing a refrigeration system using a high pressure nitrogen tank the technician should always
leak test through the low-side only
leak test through the high-side only
use a pressure regulator and safety relief value
at the nitrogen tank
never allow refrigerant to be mixed with the nitrogen
61. The maximum pressure that can be applied to a refrigeration system when pressure testing is
50 PSIG
75 PSIG
determined by the systems rated nameplate test pressures
determined by the technician
62. The safest way to charge refrigerant into a system that is running is with
vapor into the high side while under a vacuum
liquid into the high side while under a vacuum
vapor into the low side
liquid into the low side
63. When heating a refrigerant cylinder the technician should never use
warm water
an electric heat blanket
any type of open flame
none of the above
64. Refrigeration systems must be fully evacuated before charging with refrigerant
to de-pressurize the system for the expansion of refrigerant
to draw oil from the compressor during the dehydration process
to increase the rate of refrigerant flow through the expansion valve
to remove air and moisture from the system
65. A vacuum pump will lose its ability to draw a deep vacuum over time because
the oil becomes full of moisture and acids which will decrease the
capability of the vacuum pump
the refrigerant’s pressure causes a break down of the vacuum
pump oil
the vacuum in the pump causes the oil to become thinner which will
cause excessive wear
the high speed of the vacuum pump will cause a breakdown of
vacuum pump oil
66. A refrigerant service valve must be placed in the
mid position in order for the technician to access the system
back seated position in order for the technician to access the
system
front seated position in order for the technician to access the
system
all of the above
67. When using a micron gauge to measure vacuum the system should be evacuated to a level of _____ to ensure that non condensables and moisture have been adequately removed
15000 microns
10000 microns
500 microns
5000 microns
68. Amperage is a measure of
electron flow
electrical pressure
electrical power
electrical resistance
69. Voltage is the measure of
electron flow
electrical pressure
electrical power
electrical resistance
70. Wattage is a measure of
electron flow
electrical pressure
electrical power
electrical resistance
71. 746 watts equals
½ horsepower
2 horsepower
1 horsepower
none of the above
72. One kilowatt is equal to
3.412 Btus
3412 Btus
746 Btus
3.142 Btus
73. The unit of measurement for magnetic flux is?
maxwell
gilbert
capacitance
eddy current
74. On a resistive electrical circuit which law would be used to calculate I, E or R?
Boyles
Ohm’s
Charles
none of the above
75. Which of the following formula would be used to calculate amperage in resistive circuit?
E=IR
R=EI
R=E/I
I=RE
