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HVAC Air Conditioning Exit Exam > AC EXIT > Flashcards

AC EXIT Flashcards

1
Q

Heat which causes a change in temperature of a substance is called?

A

Sensible Heat

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2
Q

Heat which causes a change in state of a material without a change in temperature is called?

A

Latent Heat

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3
Q

Heat which is added to a vapor after the change of state occurs is called?

A

Super Heat

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4
Q

Heat can travel by?

A. Conduction
B. Convection
C. Radiation
D. All Of The Above

A

All Of The Above

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5
Q

Movement of heat by fluid or air is called?

A. Conduction
B. Convection
C. Radiation
D. Any Of The Above

A

Convection

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6
Q

The movement of heat by direct contact is called?

A. Radiation
B. Convection
C. Conduction
D. None Of The Above

A

Conduction

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7
Q

The standard unit for measuring the quantity of heat in a substance is?

A. Rankin
B. Fahrenheit
C. British Thermal Units (BTU’s)
D. Celsius

A

British Thermal Units (BTU’s)

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8
Q

A refrigerant gives up heat when?

A. It Condenses
B. It Evaporates
C. It Is Compressed
D. It Vaporizes

A

It Condenses

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9
Q

It is desirable for refrigerant in the suction line to be slightly superheated in order to?

A. Prevent vapor refrigerant from entering the compressor.
B. Keep the compressor warm
C. Prevent vapor refrigerant from entering the condenser
D. insure liquid refrigerant does not enter the compressor

A

Insure liquid refrigerant does not enter the compressor

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10
Q

The state of the refrigerant in the suction line should be?

A. High pressure/high temperature liquid
B. High pressure/low temperature vapor
C. Low pressure/low temperature liquid
D. Low pressure/low temperature vapor

A

Low pressure/low temperature vapor

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11
Q

The state of the refrigerant entering the condenser is?

A. High pressure/highly superheated liquid
B. High pressure/highly superheated vapor
C. High pressure/high temperature liquid
D. Low pressure/low temperature vapor

A

High pressure/highly superheated vapor

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12
Q

The evaporator..?

A. Transfers heat from the refrigerated space to the refrigerant
D. Transfers heat from the refrigerant to the refrigerated space
C. Transfers heat from the refrigerant to the ambient air
D. Transfers heat from the ambient air to the refrigerated space

A

Transfers heat from the refrigerated space to the refrigerant

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13
Q

Which of the following is not a thermodynamic property of refrigerants?

A. Critical point
B. Saturation point
C. Enthalpy
D. Flammability

A

Flammability

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14
Q

The sequential order of steps in the vapor-compression process are?

A. Expansion, condensation, compression, vaporization
B. Vaporization, expansion, condensation, compression
C. Compression, condensation, expansion, vaporization
D. Expansion, compression, vaporization, condensation

A

Compression, condensation, expansion, vaporization

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15
Q

30 pounds of R-12 refrigerant stored at 70°F. The pressure in the cylinder should be approximately?

A. 70.2 psig
B. 121.4 psig
C. 94.4 psig
D. 168.9 psig

A

70.2 psig

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16
Q

Pressures lower than atmospheric are measured in?

A. Inches of mercury (hg)
B. Microns
C. psig
D. Inches of mercury or microns

A

Inches of mercury or microns

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17
Q

Zero psia is?

A. The same as atmospheric pressure
B. Approximately 14.7 psig at sea level
C. A pressure which cannot be further reduced
D. Both A and B

A

Approximately 14.7 psig at sea level

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18
Q

Zero psig is?

A. The same as atmospheric pressure
B. Approximately 14.7 psig at sea level
C. A Pressure which cannot be further reduced
D. Both A and B

A

The same as atmospheric pressure

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19
Q

The temperature at which moisture will start to condense from the air is called?

A. Dry bulb temperature
B. Wet bulb depression
C. Dew point temperature
D. All of the above

A

Dew point temperature

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20
Q

A compound pressure gauge measures?

A. Pressure and vacuum
B. Pressure and temperature
C. Pressure and humidity
D. Wet and dry bulb temperatures

A

Pressure and vacuum

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21
Q

A mechanical shaft seal is necessary on a?

A. Semi hermetic compressor
B. Hermetic reciprocating compressor
C. Hermetic Rotary compressor
D. Open drive compressor

A

Open drive compressor

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22
Q

Liquid slugging is?

A. Noise caused by liquid refrigerant in the suction line being restricted
B. Noise caused by excessive liquid refrigerant in the condenser
C. Liquid refrigerant in the compressor clearance space
D. Excessive liquid refrigerant in the receiver

A

Liquid refrigerant in the compressor clearance space

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23
Q

The clearance space in a reciprocating compressor?

A. Has no affect on compressor capacity
B. Has an effect on compressor capacity
C. Varies depending on compressor speed
D. Is the same on all compressors

A

Has an effect on compressor capacity

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24
Q

Which of the following will cause a change in compressor capacity?

A. Suction pressure
B. Discharge pressure
C. Refrigerant vapor density
D. All of the above

A

All of the above

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25
Q

The main function of the condenser is to?

A. Store liquid refrigerant
B. Remove heat from refrigerant
C. Remove moisture from the refrigerant
D. Add heat to the refrigerant

A

Remove heat from refrigerant

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26
Q

R-12 gas enters condenser at 116.9 psig, 100°F. It leaves condenser at 80°F. It’s pressure will be?

A. 76.9 psig
B. 84.1 psig
C. 91.7 psig
D. 116.9 psig

A

116.9 psig

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27
Q

There are three basic types of condensers: Air cooled, water cooled, and ________ cooled?

A. Evaporative
B. Expansion
C. Gas
D. Double pipe pipe

A

Evaporative

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28
Q

10lbs of water pass through condenser with an entering in temperature of 80°F. It gives up 20 BTUs of heat/lb. What is the exit temp?

A. 80°F
B. 95°F
C. 100°F
D. 110°F

A

100°F

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29
Q

Heat removed from the refrigerant by the condenser is?

A. Sensible heat only
B. Latent heat only
C. Both sensible and latent heat
D. Neither sensible or latent heat

A

Both sensible and latent heat

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30
Q

Condensers operating in low temperature conditions must use which of these methods to maintain a workable head pressure?

A. Fan cycling
B. Air shutters or dampers
C. Condenser flooding
D. Any of the above

A

Any of the above

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31
Q

When testing the efficiency of an air cooled condenser the refrigerant condensing temperature should be no more than ___?

A. 30° higher than the entering air temperature
B. 80° higher than the entering air temperature
C. 100° higher than the entering air temperature
D. 5° higher than the entering air temperature

A

30° higher than the entering air temperature

32
Q

When testing the efficiency of a water cooled condenser the refrigerant condensing temperature should be no more than __?

A. 10° higher than leaving water
B. 30° higher than leaving water temperature
C. 50° higher than leaving water temperature
D. 5° higher than leaving water temperature

A

10° higher than leaving water

33
Q

The first function a condenser must perform is to ________ higher than the leaving water temperature?

A. Superheat
B. De-superheat
C. Compress
D. Sub cool

A

De-superheat

34
Q

A thermostatic expansion valve is designed to maintain?

A. Constant evaporator temperature
B. Constant refrigerant flow
C. Constant evaporator superheat
D. Constant evaporator pressure

A

Constant evaporator superheat

35
Q

The automatic expansion valve is designed to maintain?

A. Constant evaporator temperature
B. Constant refrigerant flow
C. Constant evaporator Superheat
D. Constant evaporator pressure

A

Constant evaporator pressure

36
Q

The thermostatic expansion valve has three operating pressures:

A. Evaporator pressure, spring pressure & suction pressure
B. Evaporator pressure, spring pressure & condensing pressure
C. Evaporator pressure, spring pressure & liquid pressure
D. Evaporator pressure, spring pressure & sensor bulb pressure

A

Evaporator pressure, spring pressure & sensor bulb pressure

37
Q

When mounting a thermostatic expansion valve sensor bulb

A. The contact surfaces must be clean
B. It must be tightly clamped to the suction line
C. It must be insulated from ambient temperature
D. All of the above

A

All of the above

38
Q

An air conditioning system using a thermostatic expansion valve the temperature of the evaporator outlet will be?

A. Cooler than the evaporator inlet
B. Warmer than the evaporator inlet
C. The same as the evaporator inlet
D. Unchanged by superheat

A

Warmer than the evaporator inlet

39
Q

An automatic expansion valve is best suited?

A. When the system load remains fairly constant
B. When the system load varies greatly
C. When the compressor must start often
D. When multiple evaporators are used

A

When the system load remains fairly constant

40
Q

Which of the following is not true of a capillary tube metering device?

A. They have no moving parts
B. They allow pressures to equalize after the compressor shuts down
C. They are not sensitive to system debris
D. They are sized to match system capacity

A

They are not sensitive to system debris

41
Q

A decrease in superheat causes the thermostatic expansion valve to?

A. Open
B. Close
C. Fail
D. None of the above

A

Open

42
Q

A rise in evaporator pressure causes the automatic expansion valve to?

A. Open
B. Close
C. Fail
D. None of the above

A

Close

43
Q

A low side float metering device is used?

A. On a direct expansion evaporator
B. On a flooded evaporator
C. With a thermostatic expansion valve
D. With a capillary tube

A

On a flooded evaporator

44
Q

In a direct expansion evaporator system the refrigerant enters the evaporator as a?

A. Liquid only
B. Vapor only
C. A mixture of liquid with some flash gas
D. Superheated vapor only

A

A mixture of liquid with some flash gas

45
Q

Which of the following statements about an evaporator is not true?

A. It removes heat from the air passing over the coils
B. It Dehumidifies the air passing over the coils
C. When operating below 32°F it may require defrosting
D. It is not affected by dirt or frost buildup

A

It is not affected by dirt or frost buildup

46
Q

In the evaporator..

A. Latent heat is transferred from the refrigerated space to the refrigerant
B. Latent heat is transferred from the refrigerant to the refrigerated space
C. The refrigerant changes from a vapor to a liquid
D. The refrigeration system reaches its highest pressure

A

Latent heat is transferred from the refrigerated space to the refrigerant

47
Q

A liquid line filter dryer should be placed?

A. Between the evaporator and the compressor
B. Between the compressor and the condenser
C. Between the condenser and the metering device
D. Between the metering device and the evaporator

A

Between the condenser and the metering device

48
Q

A temperature change across a filter drier indicates?

A. Normal operation
B. A refrigerant overcharge
C. A restricted filter drier
D. Any of the above

A

A restricted filter drier

49
Q

A liquid receiver is used

A. To prevent liquid refrigerant from reaching the compressor
B. To separate oil from liquid refrigerant
C. To store liquid refrigerant
D. All of the above

A

To store liquid refrigerant

50
Q

An accumulator is used?

A. To prevent liquid refrigerant from reaching the compressor
B. To separate oil from the liquid refrigerant
C. To store liquid refrigerant
D. All of the above

A

To prevent liquid refrigerant from reaching the compressor

51
Q

A sight glass would normally be located?

A. In the liquid line ahead of the metering device
B. In the suction line ahead of the compressor
C. Either A or B
D. In the liquid line before the metering device

A

In the liquid line before the metering device

52
Q

Bubbles in a sight glass could be an indication of?

A. An overcharge of refrigerant
B. Low refrigerant charge
C. Restriction in the filter drier
D. Either low charge or filter drier restriction

A

Either low charge or filter drier restriction

53
Q

A clear sight glass could indicate?

A. All liquid refrigerant
B. No refrigerant
C. Either A or B
D. Neither A or B

A

Either A or B

54
Q

Which of the following is true of a solenoid in a pump down system

A. It is located after the metering device
B. It is located before the metering device
C. It is located after the evaporator
D. It is used instead of a metering device

A

It is located before the metering device

55
Q

The purpose of an evaporator pressure regulating valve is to

A. Prevent evaporator pressure from falling below a set limit
B. Prevent freezing the water in a chiller evaporator
C. Control evaporator pressure in a multiple evaporator system
D. All of the above

A

All of the above

56
Q

A liquid to suction heat exchanger is often used to

A. Decrease superheat
B. Increase sub cooling
C. Decrease head pressure
D. All of the above

A

Increase sub cooling

57
Q

The oil pressure safety switch is operated by?

A. The sum of suction pressure and oil pressure
B. The sum of oil pressure and crank case pressure
C. The difference between crank case pressure and oil pressure
D. The difference between head pressure and oil pressure

A

The difference between crank case pressure and oil pressure

58
Q

A low pressure cut off switch is used to?

A. Establish a minimum operating pressure in the evaporator
B. Prevent condensing pressure from reaching dangerously high levels
C. Sense oil pressure in the lower portion of the compressor
D. All of the above

A

Establish a minimum operating pressure in the evaporator

59
Q

Defrosting a low temperature evaporator can be accomplished by?

A. Using hot gas from the compressor discharge line
B. Using electric heaters
C. Either A or B
D. Neither A or B

A

Either A or B

60
Q

_______ can be used for leak detection and is safe with all refrigerant?

A. Soap bubbles
B. Flammable liquid
C. Open flame
D. Acidic solution

A

Soap bubbles

61
Q

Before using an electronic leak detector

A. The system should have sufficient pressure
B. The detector must be properly calibrated
C. The detector must be compatible with the type of refrigerant used
D. All of the above

A

All of the above

62
Q

When using an electronic leak detector, the sensor probe?

A. Must be moved around suspected areas as fast as possible
B. Must be exposed to a large amount of refrigerant for calibration
C. Should be moved approximately 1 Inch per second
D. Is not affected by dirt or oil

A

Should be moved approximately 1 Inch per second

63
Q

Moisture in a refrigeration system can cause?

A. Oil breakdown
B. Corrosion
C. Acid formation
D. All of the above

A

All of the above

64
Q

In order to remove as much moisture as possible from a system?

A. Evacuate the system to 500 microns with a deep vacuum pump
B. Apply heat to areas of the system where moisture may accumulate
C. Let the vacuum pump run as long as necessary
D. All of the above

A

All of the above

65
Q

What type of gauge is used to measure a vacuum of 500 microns?

A. A high pressure gauge
B. A compound gauge
C. An electronic vacuum gauge
D. All of the above

A

An electronic vacuum gauge

66
Q

Water will vaporize at _________ temperature in a 28 in Hg vacuum?

A. 100°F
B. 10°F
C. 212°F
D. 250°F

A

100°F

67
Q

Before a vapor/compression system is open for service?

A. The refrigerant must be released to the atmosphere
B. Refrigerant must be recovered using approved equipment
C. The refrigerant may be vented only if it is a CFC
D. The refrigerant may be vented only if it is a HCFC

A

Refrigerant must be recovered using approved equipment

68
Q

To remove refrigerant in any condition from a system and store it in a external container is the definition of?

A. Refrigerant recycling
B. Refrigerant recovery
C. Refrigerant reclaiming
D. All of the above

A

Refrigerant recovery

69
Q

To process refrigerant to a level equal to new product specifications determined by chemical analysis is the definition?

A. Refrigerant recycling
B. Refrigerant recovery
C. Refrigerant reclaiming
D. All of the above

A

Refrigerant reclaiming

70
Q

To clean refrigerant for reuse by oil separation and single or multiple passes through filter driers is the definition?

A. Refrigerant recycling
B. Refrigerant recovery
C. Refrigerant reclaiming
D. All of the above

A

Refrigerant recycling

71
Q

A partially clogged capillary tube can cause?

A. High head pressure
B. A starved condenser
C. A starved evaporator
D. A flooded evaporator

A

A starved evaporator

72
Q

A hermetic system that is low on charge is indicated by?

A. A partially frosted evaporator
B. Low head pressure
C. Low suction pressure
D. All of the above

A

All of the above

73
Q

An overcharge of refrigerant will cause?

A. Increased head pressure
B. Decreased head pressure
C. Bubbles in the sight glass
D. Frost on the condenser

A

Increased head pressure

74
Q

An air conditioning system is running constantly but not cooling. Suction line is cold and the compressor is sweating?

A. Low refrigerant charge
B. Restricted return airflow or dirty evaporator
C. Both
D. Neither

A

Both

75
Q

No Cool call. Sight glass indicates full charge, liquid line is hot, unit is cycling on the motor internal overloads?

A. An overcharge of refrigerant
B. A dirty condenser
C. An inoperative condenser fan
D. Any of the above

A

Any of the above

76
Q

Compressor replaced after burn out. No cool call. Starved evaporator. Liquid line sweating leaving the filter drier?

A. Debris from the burned out compressor has clogged the dryer
B. Air in the system
C. A defective replacement compressor
D. Refrigerant overcharge

A

Debris from the burned out compressor has clogged the dryer

HVAC Air Conditioning Exit Exam (1 decks)

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