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Refrigeration excellance Flashcards

1
Q
  1. In a dry type (direct expansion) evaporator, liquid refrigerant must boil away as close to the end of the coil as possible in order to:
A

A. Operate at high-efficiency

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2
Q
  1. The difference between the temperature of the refrigerant boiling in the evaporator and the temperature at the evaporator outlet is known as
A

A. Evaporator superheat

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3
Q
  1. An expansion device that is stuck open will cause
A

D. A flooded evaporator

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4
Q
  1. When measuring evaporator superheat on a commercial system that has a long suction line, the pressure reading should be taken at the
A

A. Compressor inlet

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5
Q
  1. Superheat measurements are best taken
A

D. With the system operating at design conditions

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6
Q
  1. A technician is checking the superheat on a multi circuit evaporator and finds one of the circuits has a superheat that is higher than the others. This could be caused by
A

D. A blocked distributor

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7
Q
  1. A TXV with an external equalizer is used on
A

A. Evaporators with a high pressure drop

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8
Q
  1. Dry type evaporators operate most efficiently with the superheat setting of approximately
A

A. 8°F to 12°F

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9
Q
  1. An evaporator used to chill liquids is operating within normal superheat setting. But the system is not cooling the product properly. Which of the following is most likely the cause?
A

A. Overcharge of refrigerant

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10
Q
  1. What time interval is required between each superheat adjustment?
A

B. About 10 to 15 minutes

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11
Q
  1. A low temperature evaporator used for cooling space or product refrigeration
A

D. Must be defrosted periodically

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12
Q
  1. Some special applications use a flooded evaporator (operated full of refrigerant) in order to maintain the proper level of liquid refrigerant, a ______ type devices used.
A

D. Low side float

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13
Q
  1. A properly functioning condenser will first
A

D. De-superheat, then sub-cool

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14
Q
  1. The effect of an inefficient water cooled condenser will
A

A. Act the same as an air cooled condenser

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15
Q
  1. The refrigerant condensing temperature in a water cooled condenser is normally about _____ higher than the leaving water.
A

B. 10°F

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16
Q
  1. The refrigerant and an air cooled condenser will normally contends at approximately _____ higher temperature than the air passing over it.
A

B. 30°F

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17
Q
  1. Workable head pressure during periods of low ambient temperature can be achieved by using
A

D. Fan cycle control

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18
Q
  1. Cooling towers that pass air over water to remove system heat are limited in capacity by
A

A. Outside air wetbulb temperature

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19
Q
  1. Parallel compressors often referred to as a rack system may use
A

A. A common suction, but not a common discharge header

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20
Q
  1. The major difference between a cooling tower and an evaporative condenser is
A

D. The refrigerant is indirectly cooled in the cooling tower

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21
Q
  1. Multiple compressors provide
A

C. Capacity control

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22
Q
  1. A dirty evaporator and subsequent low evaporator pressures will cause
A

B. Low compression ratios

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23
Q
  1. The thermostatic expansion valve (TEV) maintains a constant _______ in the evaporator.
A

D. Superheat

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24
Q
  1. What type of ice is made with the commercial icemaker that uses a gear motor and auger?
A

B. Shaved ice

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25
Q
  1. Some capillary tube systems take advantage of heat exchange by soldering the capillary tube to the suction line. In order to obtain the correct superheat reading, it must be taken
A

A. After the capillary tube suction line heat exchanger

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26
Q
  1. A ______ is usually required for ultra low temperature applications.
A

D. Cascade system

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27
Q
  1. A hot gas defrost cycle can be initiated by a
A

A. Timer

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28
Q
  1. When the defrost cycle is terminated, the evaporator fans will
A

D. Delay coming on

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29
Q
  1. An off-cycle defrost method is often used on evaporators operating at a minimum of
A

C. 35°F

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30
Q
  1. Excessive frost on the evaporator causes
A

B. Reduced heat transfer

31
Q
  1. Automatic pump down systems are used to prevent
A

D. Migration of refrigerant to the crankcase during off cycles

32
Q
  1. An automatic pumpdown system requires a
A

A. Liquid line solenoid

33
Q
  1. Short cycling in a pumpdown system is most likely caused by a leaking
A

A. Liquid line solenoid valve

34
Q
  1. An evaporator pressure regulator valve (EPR valve) is a mechanical control that
A

B. Limits pressure setpoint in the evaporator

35
Q
  1. The “low ambient control” is used to control
A

B. Head pressure

36
Q
  1. The crankcase heater is used to prevent
A

A. Refrigerant migration to the compressor crankcase during the off cycle

37
Q
  1. The type of compressor that allows access to the internal components is the
A

C. Semi hermetic

38
Q
  1. Low ambient temperatures seriously affect
A

A. Water cooled units

39
Q
  1. Water cooling towers require a periodic blow down to control
A

D. Scaling

40
Q
  1. High temperature refrigeration applications normally provide box temperatures of
A

A. 47°F to 60°F

41
Q
  1. Medium temperature refrigeration applications will normally provide box temperatures of
A

D. 30°F to 42°F

42
Q
  1. Low temperature refrigeration applications, other than ice makers, will normally provide box temperatures of
A

A. 0°F to 32°F

43
Q
  1. What is the purpose of an oil separator?
A

A. To capture oil and prevent it from traveling throughout the system

44
Q
  1. Blended refrigerants should be charged into a running system
A

B. As a liquid through a throttling valve into the low side

45
Q
  1. A refrigeration system that uses the evaporator of the first stage to exchange heat with the condenser of the second stage refrigeration system is called a
A

B. Cascade system

46
Q
  1. To achieve peak efficiency and performance in a capillary tube system,
A

D. The system must be critically charged

47
Q
  1. Expendable refrigerant means
A

D. It can be used one time

48
Q
  1. If a walk-in cooler requires a high percentage of moisture in the air due to the product being stored, the logical evaporator TD would be
A

B. 20°F

49
Q
  1. “Pump down” means to capture system refrigerant in the
A

C. Condenser and/or liquid receiver

50
Q
  1. What is the normal operating position for a compressor service valve?
A

B. Back seated

51
Q
  1. The suction accumulator prevents flood back from which of the following?
A

C. Flooding after hot gas termination

52
Q
  1. When the compressor service valve is back seated, which port is closed?
A

C. Service port

53
Q
  1. When work on a refrigerator is complete, the compressor service valves should be in what position?
A

A. Back seated

54
Q
  1. What type of oil is used with HFC refrigerant?
A

A. Alkyl-benzene

55
Q
  1. On an expansion valve refrigeration system, a low pressure control can indirectly be used for
A

D. Controlling box temperature

56
Q
  1. What valve is used to connect multiple evaporators of different temperatures to a single compressor?
A

B. Evaporator pressure regulator (EPR)

57
Q
  1. What valve is used to prevent evaporator pressure from falling below a set limit?
A

B. Evaporator pressure regulator (EPR)

58
Q
  1. What valve is used to control excessive pressure entering the compressor during a hot pull down?
A

C. Crank case pressure regulator (CPR)

59
Q
  1. The oil return orifice inside a suction line accumulator is designed to
A

C. Meter liquid refrigerant and oil at acceptable rate

60
Q
  1. Why do suction line filter dryer’s have two service ports?
A

B. To enable checking pressure drop across the dryer

61
Q
  1. A thermostatic expansion valve (TXV) that creates an unstable suction pressure is said to be
A

C. Hunting

62
Q
  1. Head pressure control valves permit hot gas to travel directly to the
A

B. Evaporator

63
Q
  1. Liquid slugging of the compressor can be caused by
A

B. TXV hunting

64
Q
  1. A severe evaporator freeze up may cause
A

C. Liquid flood back

65
Q
  1. The oil separator is installed in the
A

B. Discharge line

66
Q
  1. If an oil separator is not used,
A

A. Oil traps should be installed in all vapor carrying lines

67
Q
  1. The relationship between low side absolute pressure and high side absolute pressure is called
A

C. Compression ratio

67
Q
  1. If a system has a long suction line riser, an oil trap should be installed
A

D. Every 15 to 20 feet of vertical rise

68
Q
  1. Capacity control of a large compressor can be performed with
A

C. Unloaders

69
Q
  1. Vibration eliminator’s should be installed _______ to the compressor crankshaft centerline.
A

A. Perpendicular

70
Q
  1. What pH level is considered neutral and desired for ice machine or cooling tower applications?
A

B. 7

71
Q
  1. On a rack of multiple compressors, each compressor is controlled by
A

D. CPR valve

72
Q
  1. Which refrigerant line is most sensitive to improper sizing?
A

A. Liquid line

73
Q
A

Hvac (1 decks)

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