All Tpc Flashcards
1
Q
Refrigeration is the process of __________ of the air in a confined space
A
Lowering the temperature
2
Q
The temperature of a material decreases if the material __________ and nothing else happens that would have the opposite effect
A
Contacts a colder material
3
Q
Two kinds of air conditioning are ________ and _________
A
Comfort and process
4
Q
One of the physical states of matter is _______.
Atom
Element
Gas
Molecule
A
Gas
5
Q
You can cause matter to change it’s physical state by _________ or _________ heat
A
Adding or removing
6
Q
Thermal energy that is directly related to the temperature of a material is called ________ heat.
Change of state
Latent
Potential
Sensible
A
Sensible
7
Q
A temperature of about 45°F is the same as ____°C
A
7°C
8
Q
Heat can be transferred from one place to the other by the process of _________.
Change of state
Conduction
Diffusion
Insulation
A
Conduction
9
Q
The latent heat of vaporization of a substance is the amount of heat the substance absorbs as it ________.
Condenses
Evaporates
Freezes
Melts
A
Evaporates
10
Q
A refrigeration system has been turned off for several days. Suddenly a line containing the refrigerant breaks. What happens inside the system?
Nothing because it is off
The liquid refrigerant boils
The pressure increases
The refrigerant gets warmer
A
The liquid refrigerant boils
11
Q
From the compressor, refrigerant flows to the ________
A
Condenser
12
Q
The graph below is the pressure temperature chart for refrigerant. What point shows superheating?
A
Point 1
13
Q
Compared to a dry expansion evaporator, a flooded evaporator of the same size is?
Contains no refrigerant
More efficient
Leaks refrigerant
Contains no metering device
A
More efficient
14
Q
The purpose of a cooling medium is to?
Absorb excess refrigerant vapor
Condense the water vapor in moist air
Remove heat from the compressed refrigerant vapor
Superheat the vapor
A
Remove heat from the compressed refrigerant vapor
15
Q
An automatic expansion valve is a metering device that maintains a constant pressure in the?
Compressor
Condenser
Evaporator
Surge drum
A
Evaporator
16
Q
The properties of air that are important to psychometrics are?
Enthalpy
Odor
Oxygen content
Velocity
A
Enthalpy
17
Q
In a sling psychrometer, the wet bulb temperature is usually lower than the dry bulb. If the difference is very small, you know the air is quite ________
Cool
Dry
Humid
Warm
A
Humid
18
Q
Air that is saturated is air that is at its ___________ temperature
Desired
Dew point
Lowest possible relative humidity
Optimum oxygen content
A
Dew point
19
Q
Relative humidity changes if the ______ changes, but specific humidity does not.
Barometric temperature
Dew point temperature
Dry bulb temperature
Weight of dry air
A
Dry bulb temperature
20
Q
To calculate the enthalpy of a sample of air, you must include?
Latent heat of the air
Latent heat of water vapor
Relative humidity
Specific humidity
A
Latent heat of water vapor
21
Q
In order to remove the moisture that enter a refrigeration system during repair, you must evacuate the system by using a _________ to make all the moisture vaporize
Charging hose
Manometer
Torch
Vacuum pump
A
Vacuum pump
22
Q
One useful method of detecting leaks in a refrigeration system is to use an __________ leak detector
Chronographic
Electronic
High frequency
Infrared
A
Electronic
23
Q
Relative humidity can be measured directly with an?
Dew point thermometer
Hydrometer
Hygrometer
Hygrometer psychometric chart
A
Hygrometer
24
Q
Which of the following is a direct match between an electrical value and the device used to measure it?
Current; ohhmeter
Current; wattmeter
Power; ammeter
Resistance; ohmmeter
A
Resistance; ohmmeter
25
In the options below, correctly identify the line that matched the class of work hazard to an example of that class hazard
Chemical; container of refrigerant
Mechanical; aluminum ladder
Physical; unguarded belt drive
Temperature; heatstroke
Chemical; container of refrigerant
26
If you increase the pressure of a liquid, it's ____ temperature will ______, meaning that it will boil at a higher temperature.
Saturation;increase
27
At a temperature of -30F the enthalpy of the saturated liquid refrigerant (hg) is 3.5 btu/lb. The enthaply of evaporation (hg) is 87.4 btu/lb. What is the enthaply of the saturated vapor (hg)?
90.9 btu
28
In the following diagram of a refrigeration cycle, the line between points _____ represents the amount of subcooling.
2 & 3
29
A system must provide 8 tons of refrigeration. What compressor horsepower is needed for the system?
10.3
30
Liquid refrigerant can be subcooled by transferring heat either to the atmosphere in the condenser or to the _____ in the suction-line heat exchanger.
Refrigerant vapor
31
An Ideal refrigerant has which of the following characteristics?
Non-flammable
32
In the ASHRAE standard designations of refrigerants, the?
Letter R is being replaced by letters identifying chemical structure
33
Temperature glide occurs only in ______ refrigerants.
Blended
34
ASHRE classifies refrigerants according to how hazardous they are. The most hazardous refrigerants are rated?
B3
35
When handling and storing refrigerants, you must protect yourself by?
Avoiding open flame
36
The ozone layer in the earths atmosphere is important, because it?
Absorbs ultraviolet radiation from the sun
37
CFCs also contribute to the greenhouse effect by?
Absorbing infrared radiation
38
In order to minimize the release of cfcs into the atmosphere, refrigeration service technicians must?
Recycle refrigerants on-site if possible
39
A recycled refrigerant may be placed in?
The system from which it was removed
40
During the installation of a new system, the chance of future refrigerant leaks can be reduced by?
Installing a muffler in the compressor discharge line
41
To reduce the depletion of the ozone layer, the U.S. government has implemented laws requiring?
Testing and certification of all the technicians whose work can cause the release of harmful refrigerants.
42
The EPA's final rule concerning the handling of refrigerants and refrigeration equipment requires?
Certifying the equipment used in recycling and reclaiming refrigerants
43
The compressor for an active recovery system is part of the ____. The compressor for a passive recovery system is part of the _____?
Recovery equipment; System being serviced
44
Technicians who work on residential air conditioning systems must have at least ___ certification.
Type H
45
Which of the following documents is required by the EPA?
Certification activity report
46
Which of the following is a contaminant that can be removed by a filter-drier?
Acid
47
An absorption-type desiccant holds water by means of a(n)_____action, but an adsorption type desiccant holds water by means of a(n) ______ action.
Chemical; Mechanical
48
If you mount a filter drier in a vertical suction line, the inlet should be located at the top so that ______ cannot become trapped inside.
Oil
49
When selecting a filter-drier you need to base your selection in part on?
The minimum particle size it can trap
50
When installing a filter-drier in a refrigeration system you should?
Wear safety goggles
51
You can pinpoint leaks in a new refrigeration system by charging the system with ____ and using a?
Nitrogen; Soap solution
52
When preparing to use a gauge manifold in servicing a pressurized refrigeration system you connect its high side charging hose to the?
Compressor discharge service valve
53
To check the charge in a refrigeration system, you can look at the _____in the liquid line if the charge is low you will probably see?
Sight Glass; bubbles
54
In using the deep-vacuum method of dehydrating a refrigeration system you lower the pressure to about ______ microns or less. With the vacuum pump turned off, a gradual rise in pressure tells you the system is?
1000; Not dry
55
You can tell whether you have charged a refrigeration system with the correct amount of refrigerant by checking the?
Weight of refrigerant used
56
The miscibility of a refrigerant oil is its ability to?
Mix with refrigerant
57
Oil that becomes mixed with the refrigerant in a system can cause which of the following problems?
Clogged desiccant
58
An oil separator is located between the _____ and _____in order to keep oil out of the condenser and evaporator.
Compressor; Condenser
59
Moisture in a refrigeration system causes a variety of problems including?
Blockage in cold parts of the system
60
Before you check the oil level in the sight-glass on a refrigeration compressor, you should stop the compressor for at least _____. The compressor should be ____ while you check the oil level.
Ten minutes; Stopped
61
A positive-displacement compressor uses a piston or other device to?
Compress refrigerant vapor in a chamber
62
Which of the following is a kind of kinetic-displacement compressor?
Centrifugal
63
Which of the following is part of a scroll compressor.
Swing link
64
A multiple-stage refrigeration system has more than one?
Compressor
65
When selecting a replacement compressor, you need to make sure the replacement will operate with/at the proper?
Discharge pressure
66
Among reciprocating compressors the crankshaft is usually vertical in a(n) _____ compressor, but horizontal in a(n) ______ compressor?
Full hermetic; open
67
On the pistons of reciprocating compressors, the _____rings prevent oil from reaching the compression chamber. The ______ rings prevent refrigerant from escaping around the piston during compression.
Bottom; top
68
Which of the following is a method of distributing lubricating oil in a reciprocating compressor?
Crankshaft splash
69
A cylinder unloader reduces the capacity of a reciprocating compressor by allowing refrigerant to flow through the ______ port during the _____ stroke?
Suction; compression
70
One way of reducing vibration problems in reciprocating compressors involves the use of?
Spring mounts
71
One advantage of rotary compressors over reciprocating compressors is that the?
Vibration is less
72
Slugging is the entry of _____ refrigerant into a compressor. Cavitation is the formation and collapse of ______ in a liquid flowing under pressure.
Liquid; vapor pockets
73
One purpose of the accumulator on a rotary compressor is to?
Keep dirt and debris out of the compressor
74
Helical compressors differ from rotary compressors in that they have?
No vanes
75
In a scroll compressor, one scroll is stationary and the other _____. Refrigerant enters the scrolls at the _____ and leaves at the center.
Orbits; outer edge
76
The amount of compression in a centrifugal compressor depends on the ______ the impeller, which depends in turn on the impellers ______ and rate of rotation.
Tip speed of; Diameter
77
In reverse hydrostatic sealing, the flow of ______ across the seal opposes the flow of ______ across the bearing.
Refrigerant vapor; Oil
78
In multistage centrifugal compressors, thrust loads are reduced by?
Opposing impellers
79
The purpose of a purge system on a condenser is to eliminate _____ from the refrigeration system.
Air
80
Reducing a compressors capacity by closing pre-rotation vanes raises the pressure in the systems?
Evaporator
81
Which of the following is an important factor to consider when selecting a motor to run a refrigeration compressor?
Horsepower rating
82
Which of the following motors can be used in hermetic compressors?
Capacitor-start, induction run
83
You can reverse the direction of a single-phase induction motor by?
Reversing the connection of either the starting or running winding
84
To change a dual-voltage motor to run on 240 v instead of 120 v, you need to?
Connect two running windings in series
85
A single phase motor used in a hermetic compressor has a relay to disconnect the starting winding from the circuit when the motor approaches its running speed. one kind of relay operates when the current in the ______ winding falls to a preset value. Another kind operates when the voltage across the ______ winding rises to a preset value.
Running; Starting
86
The two basic categories of motor starting devices are?
Contactors and starters
87
A reduced-voltage starter limits the current to the motor at startup in order to prevent?
Voltage drops to other equipment
88
Overload protection for compressor motors may be provided by a(n)?
External bimetallic disk
89
Crankcase heaters are especially useful on compressors that are subjected to?
Cold climates
90
Installing a suction-line accumulator can protect compressors from damage caused by?
Slugging
91
The "first rule" of preventive maintenance for compressors and related components is to?
Follow the manufacturers recommended maintenance schedules and procedures
92
Typical preventive maintenance procedures for compressors and related equipment include?
Listening for unusual noises
93
A compressor may overheat because of a?
Low oil level
94
When pumping down a compressor for service, run the compressor with the valve on the suction line closed, the close the valve on the discharge line and stop the compressor. Repeat this process until the pressure holds at _______psig.
+2 to +5
95
After disassembling a reciprocating compressor and cleaning the parts, you should inspect the parts for?
Excessive wear on bearing surfaces
96
The function of an evaporator is to _______ heat from the?
Remove; Material being cooled
97
The capacity of an evaporator is affected by the?
Cleanliness of the evaporator
98
Basic evaporator configurations depend on whether they have one or more tubes and whether or not they have?
Extended surface area
99
Multiple-circuit evaporators have headers or distributors that direct refrigerant to each coil from ______ expansion valves.
One
100
A comfort cooler ______ the humidity of moist air by cooling the air to a temperature ______ the dew point.
Reduces; below
101
Unlike a dry-expansion evaporator, refrigerant in a flooded evaporator enters as ____ liquid and exits as _____ vapor.
All; part
102
In a secondary-refrigeration system, the refrigerant removes heat from the material to be cooled. This refrigerant then transfers heat to the ______refrigerant. In the process the ___ refrigerant boils.
Secondary; primary
103
A eutectic solution is a brine in which the concentration of salt is precisely set to achieve the lowest possible?
Freezing point
104
Which evaporator arrangement offers the greatest flexibility?
Two evaporators in parallel, each with its own expansion valve
105
A cascade refrigeration system has more than one?
Compressor, Evaporator, Condenser, and Refrigerant
106
The basic law of thermodynamics that apply to refrigeration state that?
Heat flows from a warmer substance to a cooler substance
107
The net refrigeration effect can be increased by ____ the refrigerant.
Sub cooling
108
Using a heat exchanger to lower the temperature in the liquid line and raise the temperature in the suction line has the advantage of reducing?
The amount of liquid refrigerant entering the compressor
109
The amount of oil entering an evaporator can be reduced by using a?
Oil separator
110
If the fluid being cooled by an evaporator circulates through the coil rather than moving slowly or not at all, the performance of the evaporator improves because of the?
Increased temperature difference across the wall of the evaporator
111
An evaporator can be defrosted by?
Reversing the flow of refrigerant
112
To remove rust scale and sludge from a shell-and-tube evaporator you should use a _____, as necessary.
Brush
113
A water coil can be winterized by draining out the water and?
Leaving the coil dry for the winter
114
Frost buildup on an evaporator coil is increased by _____airflow and ____ air.
Low; Humid
115
Bent fins reduce the cooling capacity of an evaporator, because they?
Reduce the area exposed to air
116
The purpose of a metering device in a refrigeration system is to?
Control the flow of refrigerant into the evaporator
117
The operation of an AXV is controlled by the?
Pressure in the evaporator
118
In controlling the flow of refrigerant into a flooded evaporator, the float of a high-side float valve is located on the?
High pressure side of the valve port
119
If floodback occurs in a system using a AXV, a likely cause is?
Ice in the spring chamber above the diaphragm
120
A common problem with TXVs is ice in the valve port. The proper way to correct this problem is to?
Replace the filter drier
121
The capacity of a condenser is affected by the?
Area of contact with the cooling medium
122
Natural-draft sir cooled condensers and forced are condensers are alike in that both types?
Depend on air circulating over the coils
123
Low-ambient control in air cooled condenser can be achieved by?
Closing the dampers
124
Spring loaded relief valves protect a system against explosion by acting in response to high ____. Fusible plugs act in response to high?
Pressure; Temperature
125
Periodic maintenance of air cooled condensers includes doing which of the following every three months.
Checking belts and pulleys
126
In the _____ system, water passes through the condenser to cool the refrigerant. The water is then?
Wastewater ; Discharged to the sewer
127
In a water cooled condenser system, "makeup water" is used for?
Replacing water lost through evaporation
128
Tube-in-tube, shell-and-coil, and shell-and-tube condensers are alike in the following ways?
Liquid refrigerant collects at the bottom
129
A condenser has a pressure-relief device that _____ if the refrigerant pressure becomes to high.
Releases refrigerant
130
Generally how long should you allow a chemical cleaner to stand in a condenser?
A few hours
131
Which of the following can increase the capacity of a cooling tower or a spray pong by the greatest amount?
Increase in air velocity across the surface
132
What type of cooling tower is shown in the drawing below?
Induced draft, counter flow
133
Which components in the water-circulating system for a cooling tower or spray pond are used to keep the concentration of minerals low?
Bleed off valve
134
The capacity of a cooling tower can be controlled by means of a?
Diverting valve
135
As part of maintaining a cooling tower, you should check the _____ everyday.
Float valve for clogging
136
The basic classifications of evaporative condensers are?
Blow through and draw through
137
An evaporative condenser may include a de-superheating coil for the purpose of?
Reducing the formation of scale
138
Which of the following methods will maintain condensing pressure during cold weather operation?
Circulating water intermittently
139
What will prevent the water in an evaporative condenser from freezing during cold weather?
Installing a sump heater
140
As part of maintaining an evaporative condenser you should check the _____ every three months.
Fan blades for tightness
141
One of the main categories of water related problems in an air conditioning or refrigeration system is?
Corrosion
142
Corrosion in a water cooled system can be caused by?
Biological organisms
143
Scale formation can be reduced in a refrigeration system by adding ____ to the cooling water.
Acid
144
Bacterial and algae can be controlled in a refrigeration system by adding ____ to the cooling water.
Chlorine
145
Chemical deterioration in a wooden cooling tower can be controlled by?
Keeping the pH of circulating water in the 6.0 to 7.5 range
146
In a cooling system, one of the main lines in the piping system is the ________ line.
Liquid
147
Steel pipe is typically joined by means of ?
Flanges
148
Tubing is often preferred over piping in a cooling system, because it?
Absorbs vibration better
149
Refrigeration tubing is typically joined by?
Soldering
150
When brazing tubing to a fitting, you should first heat the ______ until the _____ melts.
Tubing; flux
151
The function of the discharge line in a refrigeration system is to?
Convey the refrigerant to the condenser
152
The "entrainment" of compressor oil is the ________ the moving refrigerant.
Drawing in and transporting of oil with
153
In order to keep entrained oil droplets moving through the piping, the refrigerant must move at _____fpm in horizontal piping and _____fpm in a vertical riser.
500-700; 750-1500
154
Refrigerant can be prevented from collecting in the compressor during the off-cycle by installing a(n) ______ in (on) the _______?
Check valve; Discharge line
155
Accessories often added to a discharge line include a?
Discharge muffler
156
Subcooling is desirable in the liquid line, because it?
Reduces the volatility of the refrigerant
157
If the pressure in the liquid line drops, flash gas can form, which can reduce the?
Refrigeration effect
158
With halocarbon refrigerants, the movement of oil is better in the liquid line than in the discharge line, because the?
Oil is miscible in most liquid refrigerants
159
A liquid receiver is used to?
Store all the refrigerant during repairs
160
The purpose of a solenoid valve in the liquid line is to stop the flow of refrigerant to the?
Evaporator
161
A double suction riser installed in a cooling system enable the system to operate at maximum load without creating excessive ____ in the suction line.
Pressure drop
162
A accumulator in the suction line traps oil and liquid refrigerant to keep it from entering the _____. A heater in the accumulator evaporate the ____?
Compressor; Refrigerant
163
An evaporator-pressure regulator valve closes part way if the pressure at the evaporator outlet becomes too ________. A crankcase pressure regulator valve closes part way if the pressure at the compressor becomes too _______?
Low; high
164
The suction line is insulated in order to prevent or reduce _____ the line
Condensation on the outside of
165
The amount of oil that can build up in the suction line of an idle single-compressor system is much _______ than the amount that can build up in an idle compressor of a multi-compressor system. To prevent damage from excessive buildup, the suction line should include a trap with a minimum rise of ______ inches.
Less; 14
166
Piping problems that result in operating problems are often caused by?
Liquid hammer
167
Which of the following expansion joints can be used in a refrigerant line?
Bellows
168
Which kind of support is appropriate for a horizontal piping run 15 ft long?
Rod type hangers
169
The problems caused by vibration in the piping of a cooling system include?
Damage to valves and controls
170
Insulation is needed on the liquid line if the line is _____ than its surroundings. The purpose of insulation on the liquid line is to prevent the loss of any _____ of the refrigerant.
Much colder; subcooling
171
What is the main function of a control system?
Maintain a variable at a setpoint
172
What are the basic components of a control system?
Sensor, controller, controlled device
173
Air conditioning and refrigeration systems are commonly controlled by ______ control
Proportional
174
Which of these control loops adjusts the setpoint automatically?
Reset system
175
The power to operate a control system may come from?
Fluid under pressure
176
An RTD responds to a change in temperature by undergoing a change in its?
Electrical resistance
177
Relative humidity is defined as the amount of moisture in the air?
Divided by the amount it can hold
178
In a pressure sensor that uses a Bourdon tube, changes in pressure are sensed by changes in the _____ of the tube?
Position of the sealed end
179
An air-conditioning system has a two-position damper in the duct bringing outside air into the building and a second two-position damper in the return-air duct. When the system shuts down, the outside air-damper should be ____ and the return air damper should be ____?
Closed; Open
180
Which of the following is an advantage of variable-speed drives over older methods of controlling the output of an air-conditioning or refrigeration system?
Proportional control can be used
181
Unlike floating control, proportional control is?
Continuous
182
The air supply for a pneumatic control system requires which of the following?
Drier
183
A PE relay is used to control a device operated by?
Electricity
184
Setting the gain of a controller determines how much a change in the ______ affects the?
Controlled variable; Controlled device
185
Adding integral action to a controller improves system performance by reducing ______. Adding derivative action improves performance by reducing ______?
Offset; Overshoot and undershoot
186
In pumpdown control, the compressor starts when the pressure ______ in the _____?
Increases; Suction line
187
The high-pressure control in the discharge line of an air-conditioning or refrigeration system responds to high pressure by?
Shutting down the compressor
188
A differential-pressure oil-safety control shuts off the compressor if the difference in pressure between the _____ and the oil pump _______ does not become high enough within a given time.
Compressor crankcase ; Discharge
189
What kind of capacity control is commonly used on large reciprocating compressors?
Cylinder unloading
190
In modulating the flow of water to hydronic terminals, the temperature control method has the advantage of?
Preventing system freeze-up in cold weather
191
In setting up a preventive maintenance program, your first step should be to?
Inspect the system in detail
192
To maintain oil pressure in a 10-hp reciprocating compressor, a ____ oil pump is used?
Positive displacement
193
To adjust the water-regulating valve on a water-cooled condenser, you should turn the adjusting screw until the ______ is at the design value. You should make this adjustment when the equipment is running at ___ load.
Head pressure; Maximum
194
The main requirements for maintaining a pneumatic control system include?
Removing and disassembling valves
195
The main requirements for maintaining an electric or electronic control system include?
Checking electrical contacts for pitting
