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7 6th Months > All Tpc > Flashcards

All Tpc Flashcards

1
Q

Refrigeration is the process of __________ of the air in a confined space

A

Lowering the temperature

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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

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3
Q

Two kinds of air conditioning are ________ and _________

A

Comfort and process

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4
Q

One of the physical states of matter is _______.

Atom
Element
Gas
Molecule

A

Gas

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5
Q

You can cause matter to change it’s physical state by _________ or _________ heat

A

Adding or removing

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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

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7
Q

A temperature of about 45°F is the same as ____°C

A

7°C

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8
Q

Heat can be transferred from one place to the other by the process of _________.

Change of state
Conduction
Diffusion
Insulation

A

Conduction

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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

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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

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11
Q

From the compressor, refrigerant flows to the ________

A

Condenser

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12
Q

The graph below is the pressure temperature chart for refrigerant. What point shows superheating?

A

Point 1

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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

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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

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15
Q

An automatic expansion valve is a metering device that maintains a constant pressure in the?

Compressor

Condenser

Evaporator

Surge drum

A

Evaporator

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16
Q

The properties of air that are important to psychometrics are?

Enthalpy

Odor

Oxygen content

Velocity

A

Enthalpy

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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

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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

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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

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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

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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

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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

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23
Q

Relative humidity can be measured directly with an?

Dew point thermometer

Hydrometer

Hygrometer

Hygrometer psychometric chart

A

Hygrometer

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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

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25
Q

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

A

Chemical; container of refrigerant

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26
Q

If you increase the pressure of a liquid, it’s ____ temperature will ______, meaning that it will boil at a higher temperature.

A

Saturation;increase

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27
Q

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)?

A

90.9 btu

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28
Q

In the following diagram of a refrigeration cycle, the line between points _____ represents the amount of subcooling.

A

2 & 3

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29
Q

A system must provide 8 tons of refrigeration. What compressor horsepower is needed for the system?

A

10.3

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30
Q

Liquid refrigerant can be subcooled by transferring heat either to the atmosphere in the condenser or to the _____ in the suction-line heat exchanger.

A

Refrigerant vapor

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31
Q

An Ideal refrigerant has which of the following characteristics?

A

Non-flammable

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32
Q

In the ASHRAE standard designations of refrigerants, the?

A

Letter R is being replaced by letters identifying chemical structure

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33
Q

Temperature glide occurs only in ______ refrigerants.

A

Blended

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34
Q

ASHRE classifies refrigerants according to how hazardous they are. The most hazardous refrigerants are rated?

A

B3

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35
Q

When handling and storing refrigerants, you must protect yourself by?

A

Avoiding open flame

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36
Q

The ozone layer in the earths atmosphere is important, because it?

A

Absorbs ultraviolet radiation from the sun

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37
Q

CFCs also contribute to the greenhouse effect by?

A

Absorbing infrared radiation

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38
Q

In order to minimize the release of cfcs into the atmosphere, refrigeration service technicians must?

A

Recycle refrigerants on-site if possible

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39
Q

A recycled refrigerant may be placed in?

A

The system from which it was removed

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40
Q

During the installation of a new system, the chance of future refrigerant leaks can be reduced by?

A

Installing a muffler in the compressor discharge line

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41
Q

To reduce the depletion of the ozone layer, the U.S. government has implemented laws requiring?

A

Testing and certification of all the technicians whose work can cause the release of harmful refrigerants.

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42
Q

The EPA’s final rule concerning the handling of refrigerants and refrigeration equipment requires?

A

Certifying the equipment used in recycling and reclaiming refrigerants

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43
Q

The compressor for an active recovery system is part of the ____. The compressor for a passive recovery system is part of the _____?

A

Recovery equipment; System being serviced

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44
Q

Technicians who work on residential air conditioning systems must have at least ___ certification.

A

Type H

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45
Q

Which of the following documents is required by the EPA?

A

Certification activity report

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46
Q

Which of the following is a contaminant that can be removed by a filter-drier?

A

Acid

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47
Q

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.

A

Chemical; Mechanical

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48
Q

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.

A

Oil

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49
Q

When selecting a filter-drier you need to base your selection in part on?

A

The minimum particle size it can trap

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50
Q

When installing a filter-drier in a refrigeration system you should?

A

Wear safety goggles

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51
Q

You can pinpoint leaks in a new refrigeration system by charging the system with ____ and using a?

A

Nitrogen; Soap solution

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52
Q

When preparing to use a gauge manifold in servicing a pressurized refrigeration system you connect its high side charging hose to the?

A

Compressor discharge service valve

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53
Q

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?

A

Sight Glass; bubbles

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54
Q

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?

A

1000; Not dry

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55
Q

You can tell whether you have charged a refrigeration system with the correct amount of refrigerant by checking the?

A

Weight of refrigerant used

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56
Q

The miscibility of a refrigerant oil is its ability to?

A

Mix with refrigerant

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57
Q

Oil that becomes mixed with the refrigerant in a system can cause which of the following problems?

A

Clogged desiccant

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58
Q

An oil separator is located between the _____ and _____in order to keep oil out of the condenser and evaporator.

A

Compressor; Condenser

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59
Q

Moisture in a refrigeration system causes a variety of problems including?

A

Blockage in cold parts of the system

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60
Q

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.

A

Ten minutes; Stopped

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61
Q

A positive-displacement compressor uses a piston or other device to?

A

Compress refrigerant vapor in a chamber

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62
Q

Which of the following is a kind of kinetic-displacement compressor?

A

Centrifugal

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63
Q

Which of the following is part of a scroll compressor.

A

Swing link

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64
Q

A multiple-stage refrigeration system has more than one?

A

Compressor

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65
Q

When selecting a replacement compressor, you need to make sure the replacement will operate with/at the proper?

A

Discharge pressure

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66
Q

Among reciprocating compressors the crankshaft is usually vertical in a(n) _____ compressor, but horizontal in a(n) ______ compressor?

A

Full hermetic; open

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67
Q

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.

A

Bottom; top

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68
Q

Which of the following is a method of distributing lubricating oil in a reciprocating compressor?

A

Crankshaft splash

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69
Q

A cylinder unloader reduces the capacity of a reciprocating compressor by allowing refrigerant to flow through the ______ port during the _____ stroke?

A

Suction; compression

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70
Q

One way of reducing vibration problems in reciprocating compressors involves the use of?

A

Spring mounts

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71
Q

One advantage of rotary compressors over reciprocating compressors is that the?

A

Vibration is less

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72
Q

Slugging is the entry of _____ refrigerant into a compressor. Cavitation is the formation and collapse of ______ in a liquid flowing under pressure.

A

Liquid; vapor pockets

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73
Q

One purpose of the accumulator on a rotary compressor is to?

A

Keep dirt and debris out of the compressor

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74
Q

Helical compressors differ from rotary compressors in that they have?

A

No vanes

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75
Q

In a scroll compressor, one scroll is stationary and the other _____. Refrigerant enters the scrolls at the _____ and leaves at the center.

A

Orbits; outer edge

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76
Q

The amount of compression in a centrifugal compressor depends on the ______ the impeller, which depends in turn on the impellers ______ and rate of rotation.

A

Tip speed of; Diameter

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77
Q

In reverse hydrostatic sealing, the flow of ______ across the seal opposes the flow of ______ across the bearing.

A

Refrigerant vapor; Oil

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78
Q

In multistage centrifugal compressors, thrust loads are reduced by?

A

Opposing impellers

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79
Q

The purpose of a purge system on a condenser is to eliminate _____ from the refrigeration system.

A

Air

80
Q

Reducing a compressors capacity by closing pre-rotation vanes raises the pressure in the systems?

A

Evaporator

81
Q

Which of the following is an important factor to consider when selecting a motor to run a refrigeration compressor?

A

Horsepower rating

82
Q

Which of the following motors can be used in hermetic compressors?

A

Capacitor-start, induction run

83
Q

You can reverse the direction of a single-phase induction motor by?

A

Reversing the connection of either the starting or running winding

84
Q

To change a dual-voltage motor to run on 240 v instead of 120 v, you need to?

A

Connect two running windings in series

85
Q

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.

A

Running; Starting

86
Q

The two basic categories of motor starting devices are?

A

Contactors and starters

87
Q

A reduced-voltage starter limits the current to the motor at startup in order to prevent?

A

Voltage drops to other equipment

88
Q

Overload protection for compressor motors may be provided by a(n)?

A

External bimetallic disk

89
Q

Crankcase heaters are especially useful on compressors that are subjected to?

A

Cold climates

90
Q

Installing a suction-line accumulator can protect compressors from damage caused by?

A

Slugging

91
Q

The “first rule” of preventive maintenance for compressors and related components is to?

A

Follow the manufacturers recommended maintenance schedules and procedures

92
Q

Typical preventive maintenance procedures for compressors and related equipment include?

A

Listening for unusual noises

93
Q

A compressor may overheat because of a?

A

Low oil level

94
Q

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.

A

+2 to +5

95
Q

After disassembling a reciprocating compressor and cleaning the parts, you should inspect the parts for?

A

Excessive wear on bearing surfaces

96
Q

The function of an evaporator is to _______ heat from the?

A

Remove; Material being cooled

97
Q

The capacity of an evaporator is affected by the?

A

Cleanliness of the evaporator

98
Q

Basic evaporator configurations depend on whether they have one or more tubes and whether or not they have?

A

Extended surface area

99
Q

Multiple-circuit evaporators have headers or distributors that direct refrigerant to each coil from ______ expansion valves.

A

One

100
Q

A comfort cooler ______ the humidity of moist air by cooling the air to a temperature ______ the dew point.

A

Reduces; below

101
Q

Unlike a dry-expansion evaporator, refrigerant in a flooded evaporator enters as ____ liquid and exits as _____ vapor.

A

All; part

102
Q

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.

A

Secondary; primary

103
Q

A eutectic solution is a brine in which the concentration of salt is precisely set to achieve the lowest possible?

A

Freezing point

104
Q

Which evaporator arrangement offers the greatest flexibility?

A

Two evaporators in parallel, each with its own expansion valve

105
Q

A cascade refrigeration system has more than one?

A

Compressor, Evaporator, Condenser, and Refrigerant

106
Q

The basic law of thermodynamics that apply to refrigeration state that?

A

Heat flows from a warmer substance to a cooler substance

107
Q

The net refrigeration effect can be increased by ____ the refrigerant.

A

Sub cooling

108
Q

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?

A

The amount of liquid refrigerant entering the compressor

109
Q

The amount of oil entering an evaporator can be reduced by using a?

A

Oil separator

110
Q

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?

A

Increased temperature difference across the wall of the evaporator

111
Q

An evaporator can be defrosted by?

A

Reversing the flow of refrigerant

112
Q

To remove rust scale and sludge from a shell-and-tube evaporator you should use a _____, as necessary.

A

Brush

113
Q

A water coil can be winterized by draining out the water and?

A

Leaving the coil dry for the winter

114
Q

Frost buildup on an evaporator coil is increased by _____airflow and ____ air.

A

Low; Humid

115
Q

Bent fins reduce the cooling capacity of an evaporator, because they?

A

Reduce the area exposed to air

116
Q

The purpose of a metering device in a refrigeration system is to?

A

Control the flow of refrigerant into the evaporator

117
Q

The operation of an AXV is controlled by the?

A

Pressure in the evaporator

118
Q

In controlling the flow of refrigerant into a flooded evaporator, the float of a high-side float valve is located on the?

A

High pressure side of the valve port

119
Q

If floodback occurs in a system using a AXV, a likely cause is?

A

Ice in the spring chamber above the diaphragm

120
Q

A common problem with TXVs is ice in the valve port. The proper way to correct this problem is to?

A

Replace the filter drier

121
Q

The capacity of a condenser is affected by the?

A

Area of contact with the cooling medium

122
Q

Natural-draft sir cooled condensers and forced are condensers are alike in that both types?

A

Depend on air circulating over the coils

123
Q

Low-ambient control in air cooled condenser can be achieved by?

A

Closing the dampers

124
Q

Spring loaded relief valves protect a system against explosion by acting in response to high ____. Fusible plugs act in response to high?

A

Pressure; Temperature

125
Q

Periodic maintenance of air cooled condensers includes doing which of the following every three months.

A

Checking belts and pulleys

126
Q

In the _____ system, water passes through the condenser to cool the refrigerant. The water is then?

A

Wastewater ; Discharged to the sewer

127
Q

In a water cooled condenser system, “makeup water” is used for?

A

Replacing water lost through evaporation

128
Q

Tube-in-tube, shell-and-coil, and shell-and-tube condensers are alike in the following ways?

A

Liquid refrigerant collects at the bottom

129
Q

A condenser has a pressure-relief device that _____ if the refrigerant pressure becomes to high.

A

Releases refrigerant

130
Q

Generally how long should you allow a chemical cleaner to stand in a condenser?

A

A few hours

131
Q

Which of the following can increase the capacity of a cooling tower or a spray pong by the greatest amount?

A

Increase in air velocity across the surface

132
Q

What type of cooling tower is shown in the drawing below?

A

Induced draft, counter flow

133
Q

Which components in the water-circulating system for a cooling tower or spray pond are used to keep the concentration of minerals low?

A

Bleed off valve

134
Q

The capacity of a cooling tower can be controlled by means of a?

A

Diverting valve

135
Q

As part of maintaining a cooling tower, you should check the _____ everyday.

A

Float valve for clogging

136
Q

The basic classifications of evaporative condensers are?

A

Blow through and draw through

137
Q

An evaporative condenser may include a de-superheating coil for the purpose of?

A

Reducing the formation of scale

138
Q

Which of the following methods will maintain condensing pressure during cold weather operation?

A

Circulating water intermittently

139
Q

What will prevent the water in an evaporative condenser from freezing during cold weather?

A

Installing a sump heater

140
Q

As part of maintaining an evaporative condenser you should check the _____ every three months.

A

Fan blades for tightness

141
Q

One of the main categories of water related problems in an air conditioning or refrigeration system is?

A

Corrosion

142
Q

Corrosion in a water cooled system can be caused by?

A

Biological organisms

143
Q

Scale formation can be reduced in a refrigeration system by adding ____ to the cooling water.

A

Acid

144
Q

Bacterial and algae can be controlled in a refrigeration system by adding ____ to the cooling water.

A

Chlorine

145
Q

Chemical deterioration in a wooden cooling tower can be controlled by?

A

Keeping the pH of circulating water in the 6.0 to 7.5 range

146
Q

In a cooling system, one of the main lines in the piping system is the ________ line.

A

Liquid

147
Q

Steel pipe is typically joined by means of ?

A

Flanges

148
Q

Tubing is often preferred over piping in a cooling system, because it?

A

Absorbs vibration better

149
Q

Refrigeration tubing is typically joined by?

A

Soldering

150
Q

When brazing tubing to a fitting, you should first heat the ______ until the _____ melts.

A

Tubing; flux

151
Q

The function of the discharge line in a refrigeration system is to?

A

Convey the refrigerant to the condenser

152
Q

The “entrainment” of compressor oil is the ________ the moving refrigerant.

A

Drawing in and transporting of oil with

153
Q

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.

A

500-700; 750-1500

154
Q

Refrigerant can be prevented from collecting in the compressor during the off-cycle by installing a(n) ______ in (on) the _______?

A

Check valve; Discharge line

155
Q

Accessories often added to a discharge line include a?

A

Discharge muffler

156
Q

Subcooling is desirable in the liquid line, because it?

A

Reduces the volatility of the refrigerant

157
Q

If the pressure in the liquid line drops, flash gas can form, which can reduce the?

A

Refrigeration effect

158
Q

With halocarbon refrigerants, the movement of oil is better in the liquid line than in the discharge line, because the?

A

Oil is miscible in most liquid refrigerants

159
Q

A liquid receiver is used to?

A

Store all the refrigerant during repairs

160
Q

The purpose of a solenoid valve in the liquid line is to stop the flow of refrigerant to the?

A

Evaporator

161
Q

A double suction riser installed in a cooling system enable the system to operate at maximum load without creating excessive ____ in the suction line.

A

Pressure drop

162
Q

A accumulator in the suction line traps oil and liquid refrigerant to keep it from entering the _____. A heater in the accumulator evaporate the ____?

A

Compressor; Refrigerant

163
Q

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 _______?

A

Low; high

164
Q

The suction line is insulated in order to prevent or reduce _____ the line

A

Condensation on the outside of

165
Q

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.

A

Less; 14

166
Q

Piping problems that result in operating problems are often caused by?

A

Liquid hammer

167
Q

Which of the following expansion joints can be used in a refrigerant line?

A

Bellows

168
Q

Which kind of support is appropriate for a horizontal piping run 15 ft long?

A

Rod type hangers

169
Q

The problems caused by vibration in the piping of a cooling system include?

A

Damage to valves and controls

170
Q

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.

A

Much colder; subcooling

171
Q

What is the main function of a control system?

A

Maintain a variable at a setpoint

172
Q

What are the basic components of a control system?

A

Sensor, controller, controlled device

173
Q

Air conditioning and refrigeration systems are commonly controlled by ______ control

A

Proportional

174
Q

Which of these control loops adjusts the setpoint automatically?

A

Reset system

175
Q

The power to operate a control system may come from?

A

Fluid under pressure

176
Q

An RTD responds to a change in temperature by undergoing a change in its?

A

Electrical resistance

177
Q

Relative humidity is defined as the amount of moisture in the air?

A

Divided by the amount it can hold

178
Q

In a pressure sensor that uses a Bourdon tube, changes in pressure are sensed by changes in the _____ of the tube?

A

Position of the sealed end

179
Q

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 ____?

A

Closed; Open

180
Q

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?

A

Proportional control can be used

181
Q

Unlike floating control, proportional control is?

A

Continuous

182
Q

The air supply for a pneumatic control system requires which of the following?

A

Drier

183
Q

A PE relay is used to control a device operated by?

A

Electricity

184
Q

Setting the gain of a controller determines how much a change in the ______ affects the?

A

Controlled variable; Controlled device

185
Q

Adding integral action to a controller improves system performance by reducing ______. Adding derivative action improves performance by reducing ______?

A

Offset; Overshoot and undershoot

186
Q

In pumpdown control, the compressor starts when the pressure ______ in the _____?

A

Increases; Suction line

187
Q

The high-pressure control in the discharge line of an air-conditioning or refrigeration system responds to high pressure by?

A

Shutting down the compressor

188
Q

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.

A

Compressor crankcase ; Discharge

189
Q

What kind of capacity control is commonly used on large reciprocating compressors?

A

Cylinder unloading

190
Q

In modulating the flow of water to hydronic terminals, the temperature control method has the advantage of?

A

Preventing system freeze-up in cold weather

191
Q

In setting up a preventive maintenance program, your first step should be to?

A

Inspect the system in detail

192
Q

To maintain oil pressure in a 10-hp reciprocating compressor, a ____ oil pump is used?

A

Positive displacement

193
Q

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.

A

Head pressure; Maximum

194
Q

The main requirements for maintaining a pneumatic control system include?

A

Removing and disassembling valves

195
Q

The main requirements for maintaining an electric or electronic control system include?

A

Checking electrical contacts for pitting

7 6th Months (1 decks)

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