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Refrigerant Machine Operator Practical > Practice Test > Flashcards

Practice Test Flashcards

1
Q

Horsepower will increase as ____ and decrease as ____

A

Increases as the head pressure increases and dcreases as suction pressure increases

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2
Q

A solenoid valve ____

A

does not vary the flow of refrigerant into the evaporator

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3
Q

The TEV ____

A

Modulates and controls the flow of refrigerant into the evaporator

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4
Q

If you use an automatic exspansion valve with a variable load you will ____

A

Starve the evaporaot

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5
Q

An automatic expansion valve with a variable load will ____

A

Starve the evaporator

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6
Q

An automatic expansion valve maintains ____

A

constant evaporator pressure

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7
Q

If the evaporator doesn’t respond to the adjustments of the TEV it may be due ____

A

To oil logged on the low side

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8
Q

Noncondensibles can cause ____

A

High head pressure

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9
Q

The purpose of having a compressors in a cascade system is to operate at ____

A

Very low temperatures

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10
Q

A pressure relief valve is better than a fusible plug because ____

A

A fusible plug cannot be reset

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11
Q

If the TEV’s spring was to break it would ____

A

Flood the evaporator and raise suction pressures

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12
Q

The TEV equalizer Line makes up for the ____

A

Pressure drop in the evaporator

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13
Q

Semi Hermetic compressors have the advantage over hermetic because

A

They can be serviced on site

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14
Q

When using a portable compressor recovery unit to remove vapor the ____

A

Vapor density is decreased

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15
Q

Unloaders are used to ____

A

Decrease capacity

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16
Q

The amount of pressure that flows through the orifice plates is determined by the ____

A

Difference in pressure between the high and low sides

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17
Q

A TEV restricts the amount of refrigerant from the ____

A

High to low side

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18
Q

A halide torch turns from ____ when a leak is detected

A

Blue to green or purple

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19
Q

A rectifier turns ____

A

AC voltage to DC voltage

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20
Q

A thermostat will ____

A

Cycle compressors

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21
Q

The main reason for a crankcase breather line is to prevent ____

A

Oil from slugging in the compressor

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22
Q

The middle port on a manifold gauge will be connected to the ____

A

Recovery cylinder or the charging cylinder

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23
Q

A forced draft cooling tower is better than a natural draft because it is ____

A

Smaller and not affected by prevailing winds

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24
Q

Solenoids and motors work on ____

A

Watts

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25
Q

R-22 at 38 degrees is ____

A

65.6 psi

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26
Q

A purge unit disposes of ____

A

Non condensibles

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27
Q

An overcharge of refrigerant can cause ____

A

High head pressure

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28
Q

A sling psychrometer if both wet and dry bulb temps were the same would indicate ____

A

A lot of relative humidity

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29
Q

A vertical shell and tube condenser uses a ____ to force down the tubes proving good heat transfer

A

Swirler at the top of the water box

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30
Q

The muffler is located ____

A

Between the compressor and the condenser

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31
Q

A brine solution with a ph of 7.8 is ____

A

Slightly alkaline

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32
Q

If the TEV sensing bulb is clamped at the center of the evaporator it cause ____

A

excessive superheat

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33
Q

Subcooling indicates the performance of the ____

A

Condenser

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34
Q

A stuffing box lantern is made of ____

A

Metal with oil circulating through it

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35
Q

TEV’s are rates in ____

A

Tons of refrigeration

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36
Q

An anemometer measures ____

A

Air velocity

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37
Q

You check motor windings with an ____

A

Ohmmeter

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38
Q

A filter drier removes ____

A

Moisture, acids, and contaminants

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39
Q

When removing a service valve stem cap remove ____

A

Slowly

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40
Q

Charging liquid using a gauge manifold the ____

A

High side is open and the low side is closed

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41
Q

In a 3 stage centrifugal chiller the ____

A

Pressure increases as it reaches its final stage

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42
Q

Inducing draft cooling tower the lowest temp attainable for cooling tower water is ____

A

Higher than the wet bulb

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43
Q

A compressor safety head is a ____

A

Pressure relief device

44
Q

A centrifugal machine is characterized by ____

A

High volume and low pressure

45
Q

If condenser pressure is high and another pump has to be turned in you would have the ____

A

Suction valve be completely opened and the discharge valve opened to a throttling position

46
Q

If you disconnected the external equalizer on a TEV you would ____

A

Starve the evaporator

47
Q

You achieve capacity control on a reciprocating compressor by ____

A

Opening suction valves by using some form of control

48
Q

A sling psychrometer is used to measure ____

A

Relative humidity

49
Q

The ratio of actual water vapor in the atmosphere to the saturation pressure is called ____

A

Relative humidity

50
Q

Refrigerant effect is always lower than latent heat because ____

A

Heat required to cool the refrigerant from compressor discharge to evaporator temperature is subtracted from latent heat

51
Q

You use a TEV with an external equalizer when there is more than a ____

A

2.5 pressure drop through the evaporator coil

52
Q

Cylinder Unloaders are used for

A

Controlling capacity

53
Q

R-22 head pressure with condenser water temperature if 85 degrees is ____

A

200-215 psi

54
Q

When you run 2 pumps in parallel you ____. Pressure is the same when running 1 or 2 pumps

A

Increase total flow rate (gpm)

55
Q

Frost in the suction line and compressor could be caused by the ____

A

TEV being opened to wide

56
Q

If cooling tower is not chemically treated it could cause ____

A

Bacteria growth and rusty pipes

57
Q

The low-pressure control _____ off and on

A

Cycles the compressor

58
Q

____ require an oxygen deprivation sensor (R-12, R-12, R-22, R-134A)

A

All group 1 refrigerants

59
Q

A low pressure chiller’s rupture disc is set at ____

A

15 psi

60
Q

An automatic purge unit is required for systems that operate ____

A

Below atmospheric pressure (in a vacuum)

61
Q

An undesirable property in a refrigerant is ____

A

Low latent heat

62
Q

Scale particles lodged in a TEV could cause ____

A

High super heat

63
Q

High head pressure and temperature could be caused by ____

A

Dirty condenser tubes

64
Q

If wet bulb temperature decreases it can ____

A

Lower the temperature of the cooling tower water

65
Q

You can always charge refrigerant into the ____

A

Low side

66
Q

Clogged eliminator fins on a cooling tower could lead to a ____

A

Higher temperature supply

67
Q

A jet ejector if restricted will have ____

A

Insufficient head to lift the oil back to the oil sump

68
Q

The low side gauge (saturation pressure) can be used to ____

A

Estimate chill water temperature

69
Q

Water tube leaks a low-pressure chiller cab be found with a ____

A

Hydrostatic tube test

70
Q

R-11 and R-123 refrigerants are ____

A

Oxygen depleting, heavier than air, and class 1 and class 11 substances

71
Q

A centrifugal chiller purge unit first ______________

A

Takes a combination of air and refrigerant from the top of the condenser, then removed air and non condensibles, and finally returns liquid refrigerant back to the condenser

72
Q

_______ are use to defrost evaporators

A

Electric resistance heaters (resistor circuit)

73
Q

Low condensing pressure is not good because ____

A

Expansion valves will not feed properly

74
Q

An in-line refrigerant cleaning system is advisable because ____

A

Refrigerant reacts with lube oil

75
Q

If the water pump is facilitating this problem could be caused by ____

A

A faulty water level control

76
Q

Capacitors are devices which have the ability to ____

A

Store electricity and used to start motors

77
Q

The refrigerant with the highest latent heat is ____

A

Ammonia

78
Q

____ are electric devices which change the value of AC voltage to another AC voltage

A

Transformers

79
Q

The maximum pressure to leak test low pressure chillers is ____

A

10 psig

80
Q

Under EPA regulations you can pressurize a system for a ____

A

Non major reissue with nitrogen

81
Q

Under EPA regulations replacement of an evaporator coil is ____

A

Always considered a major repair

82
Q

R-11 at 14.7 psia (0 psig) will boil at approximately ____

A

74.5 degrees

83
Q

If a system is excessively cycling ,crankcase temp is high, discharge is low and suction is high this could be caused by ____

A

Faulty compressor valves

84
Q

Centrifugal compressors can control capacity with ____ and/or ____

A

Variable guide vanes and/or variable speed motors

85
Q

On a reciprocating compressor there are stop valves on the ____

A

Inlet (suction side) and the outlet (discharge side)

86
Q

Refrigerant is added to a low-pressure centrifugal chiller through the ____

A

Evaporator charging valve

87
Q

You can store ___% refrigerant on site

A

20%

88
Q

Before a low-pressure appliance is dismantled and salvaged ____

A

Refrigerant must be recovered

89
Q

Chill water pumped are ____

A

Always insulated

90
Q

Compound gauges measure ____

A

positive and negative pressure

91
Q

Oil pressure should be at least ____ in a reciprocating compressor

A

15 to 30 pounds above the suction pressure

92
Q

The motor is connected to the pump with a ____

A

Flexible coupling

93
Q

She’ll and COIL condensers are not mechanically serviceable and must be cleaned ____

A

Chemically

94
Q

Shell and TUBE condensers can be _____

A

Mechanically cleaned with brushes

95
Q

Water regulating valves work off of ____

A

Head pressure

96
Q

Outdoor cooling towers have ____ to prevent freezing

A

Heater coils

97
Q

A refrigeration system with a cooling tower the heat from the building sis rejected as the ____ in the cooling tower

A

Heat of evaporation

98
Q

An older type of cylinder Unloaders is designed to control ____

A

Cylinder clearance pockets

99
Q

An efficient condenser runs with a ____

A

Low condenser pressure

100
Q

If a unit using a low side float was short cycling it could need ___

A

Additional refrigerant to be charged

101
Q

A disadvantage if fusible plug is that it ____

A

Only works on temperature

102
Q

If a centrifugal pump is running fine at full discharge but if throttled it loses flow a ____ could be the cause

A

Clogged strainer

103
Q

A compressor stuffing box prevents the ____

A

Leaking of refrigerant vapor

104
Q

The AEV works on 2 pressures ____

A

Evaporator pressure is opening pressure and spring pressure is closing pressure

105
Q

The most superheat occurs after when ____

A

Boiling is complete

106
Q

High pressure is found ____ and low pressure is ____

A

Above the valve plate and below the valve plate

107
Q

Automatic water regulating valves vary water flow according to ____

A

Condenser Head Pressure

Refrigerant Machine Operator Practical (5 decks)

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