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Refrigerant Machine Operator Practical > Practice Test > Flashcards

Practice Test Flashcards

(107 cards)

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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
R-22 at 38 degrees is ____
65.6 psi
26
A purge unit disposes of ____
Non condensibles
27
An overcharge of refrigerant can cause ____
High head pressure
28
A sling psychrometer if both wet and dry bulb temps were the same would indicate ____
A lot of relative humidity
29
A vertical shell and tube condenser uses a ____ to force down the tubes proving good heat transfer
Swirler at the top of the water box
30
The muffler is located ____
Between the compressor and the condenser
31
A brine solution with a ph of 7.8 is ____
Slightly alkaline
32
If the TEV sensing bulb is clamped at the center of the evaporator it cause ____
excessive superheat
33
Subcooling indicates the performance of the ____
Condenser
34
A stuffing box lantern is made of ____
Metal with oil circulating through it
35
TEV’s are rates in ____
Tons of refrigeration
36
An anemometer measures ____
Air velocity
37
You check motor windings with an ____
Ohmmeter
38
A filter drier removes ____
Moisture, acids, and contaminants
39
When removing a service valve stem cap remove ____
Slowly
40
Charging liquid using a gauge manifold the ____
High side is open and the low side is closed
41
In a 3 stage centrifugal chiller the ____
Pressure increases as it reaches its final stage
42
Inducing draft cooling tower the lowest temp attainable for cooling tower water is ____
Higher than the wet bulb
43
A compressor safety head is a ____
Pressure relief device
44
A centrifugal machine is characterized by ____
High volume and low pressure
45
If condenser pressure is high and another pump has to be turned in you would have the ____
Suction valve be completely opened and the discharge valve opened to a throttling position
46
If you disconnected the external equalizer on a TEV you would ____
Starve the evaporator
47
You achieve capacity control on a reciprocating compressor by ____
Opening suction valves by using some form of control
48
A sling psychrometer is used to measure ____
Relative humidity
49
The ratio of actual water vapor in the atmosphere to the saturation pressure is called ____
Relative humidity
50
Refrigerant effect is always lower than latent heat because ____
Heat required to cool the refrigerant from compressor discharge to evaporator temperature is subtracted from latent heat
51
You use a TEV with an external equalizer when there is more than a ____
2.5 pressure drop through the evaporator coil
52
Cylinder Unloaders are used for
Controlling capacity
53
R-22 head pressure with condenser water temperature if 85 degrees is ____
200-215 psi
54
When you run 2 pumps in parallel you ____. Pressure is the same when running 1 or 2 pumps
Increase total flow rate (gpm)
55
Frost in the suction line and compressor could be caused by the ____
TEV being opened to wide
56
If cooling tower is not chemically treated it could cause ____
Bacteria growth and rusty pipes
57
The low-pressure control _____ off and on
Cycles the compressor
58
____ require an oxygen deprivation sensor (R-12, R-12, R-22, R-134A)
All group 1 refrigerants
59
A low pressure chiller’s rupture disc is set at ____
15 psi
60
An automatic purge unit is required for systems that operate ____
Below atmospheric pressure (in a vacuum)
61
An undesirable property in a refrigerant is ____
Low latent heat
62
Scale particles lodged in a TEV could cause ____
High super heat
63
High head pressure and temperature could be caused by ____
Dirty condenser tubes
64
If wet bulb temperature decreases it can ____
Lower the temperature of the cooling tower water
65
You can always charge refrigerant into the ____
Low side
66
Clogged eliminator fins on a cooling tower could lead to a ____
Higher temperature supply
67
A jet ejector if restricted will have ____
Insufficient head to lift the oil back to the oil sump
68
The low side gauge (saturation pressure) can be used to ____
Estimate chill water temperature
69
Water tube leaks a low-pressure chiller cab be found with a ____
Hydrostatic tube test
70
R-11 and R-123 refrigerants are ____
Oxygen depleting, heavier than air, and class 1 and class 11 substances
71
A centrifugal chiller purge unit first ______________
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
_______ are use to defrost evaporators
Electric resistance heaters (resistor circuit)
73
Low condensing pressure is not good because ____
Expansion valves will not feed properly
74
An in-line refrigerant cleaning system is advisable because ____
Refrigerant reacts with lube oil
75
If the water pump is facilitating this problem could be caused by ____
A faulty water level control
76
Capacitors are devices which have the ability to ____
Store electricity and used to start motors
77
The refrigerant with the highest latent heat is ____
Ammonia
78
____ are electric devices which change the value of AC voltage to another AC voltage
Transformers
79
The maximum pressure to leak test low pressure chillers is ____
10 psig
80
Under EPA regulations you can pressurize a system for a ____
Non major reissue with nitrogen
81
Under EPA regulations replacement of an evaporator coil is ____
Always considered a major repair
82
R-11 at 14.7 psia (0 psig) will boil at approximately ____
74.5 degrees
83
If a system is excessively cycling ,crankcase temp is high, discharge is low and suction is high this could be caused by ____
Faulty compressor valves
84
Centrifugal compressors can control capacity with ____ and/or ____
Variable guide vanes and/or variable speed motors
85
On a reciprocating compressor there are stop valves on the ____
Inlet (suction side) and the outlet (discharge side)
86
Refrigerant is added to a low-pressure centrifugal chiller through the ____
Evaporator charging valve
87
You can store ___% refrigerant on site
20%
88
Before a low-pressure appliance is dismantled and salvaged ____
Refrigerant must be recovered
89
Chill water pumped are ____
Always insulated
90
Compound gauges measure ____
positive and negative pressure
91
Oil pressure should be at least ____ in a reciprocating compressor
15 to 30 pounds above the suction pressure
92
The motor is connected to the pump with a ____
Flexible coupling
93
She’ll and COIL condensers are not mechanically serviceable and must be cleaned ____
Chemically
94
Shell and TUBE condensers can be _____
Mechanically cleaned with brushes
95
Water regulating valves work off of ____
Head pressure
96
Outdoor cooling towers have ____ to prevent freezing
Heater coils
97
A refrigeration system with a cooling tower the heat from the building sis rejected as the ____ in the cooling tower
Heat of evaporation
98
An older type of cylinder Unloaders is designed to control ____
Cylinder clearance pockets
99
An efficient condenser runs with a ____
Low condenser pressure
100
If a unit using a low side float was short cycling it could need ___
Additional refrigerant to be charged
101
A disadvantage if fusible plug is that it ____
Only works on temperature
102
If a centrifugal pump is running fine at full discharge but if throttled it loses flow a ____ could be the cause
Clogged strainer
103
A compressor stuffing box prevents the ____
Leaking of refrigerant vapor
104
The AEV works on 2 pressures ____
Evaporator pressure is opening pressure and spring pressure is closing pressure
105
The most superheat occurs after when ____
Boiling is complete
106
High pressure is found ____ and low pressure is ____
Above the valve plate and below the valve plate
107
Automatic water regulating valves vary water flow according to ____
Condenser Head Pressure

Refrigerant Machine Operator Practical (5 decks)

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