Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

UA HVAC Star Exam Prep > UA Local 140 Practice Test 1 > Flashcards

UA Local 140 Practice Test 1 Flashcards

1
Q

. Which of the following is true when there is excessive vibration of rotating machinery?

A

It may lead to fatigue failures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Which is the best practice to follow when one bearing fails is a multiple bearing application?

A

Replace all bearings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Thrust loads are____ to a shaft.

A

Parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

When installing split tapered bushings, where should you apply anti-seize lubricant?

A

none of the parts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Which is the final step in installing a pillow block bearing?

A

tighten bearings to shaft

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

The mechanical seal in a centrifugal pump is necessary to prevent which of the following events?

A

fluid leaking out around the shaft

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

If a mechanical seal has just been replaced and the pump leaks slightly at start-up, which step should you take

A

a. allow the pump to continue running for a short period to see if the leak stops

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How should the belts in a multiple V-belt application be replaced?

A

as a set

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

While performing a visual inspection of a belt driven fan, which of the following is NOT a requirement of the
inspection?

A

manufacturer of the belt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Using a belt tensioning tool, which factor is NOT taken into account when adjusting belt tension?

A

number of belts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

The horsepower of the motor is transferred from the V Belt to the fan pulley where on the belt?

A

the sides of the belt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

A belt drive on a motor driven fan has a drive sheave of 3” pitch diameter on the motor. The sheave of the fan shaft has a pitch diameter of 5”, when the motor speed is 1720 RPM, what is the fan speed?

RPM of drive=diamerterof driver X RPM of driver
Divided by Diameter of driven

A

1032 RPM

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which of the following is the major cause of high speed rotating equipment failure?

A

imbalance and misalignment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Which is the first step of shaft alignment of a direct drive motor?

A

Angular in elevation view

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Which tool would not be used to align a pump?

A

voltmeter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which is the first step of shaft alignment of a direct drive motor?

A

flexible base

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which of these statements is TRUE of a coupling which is NOT properly aligned?

A

it will almost certainly fail more quickly than it should and could wear out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which of these statements is true of coupling guards?

A

they should be kept in place for the life of the equipment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

A tire style coupling is commonly used on which of these?

A

cooling towers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which of these is the tool to use to move a coupling half that is seized on the motor shaft?

A

hammer with softening tool

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Which of the following times situations does NOT require a re-check of the pump coupling alignment?

A

after a motor and pump are at the normal operating temp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Potential difference refers to the energy difference in electrons between two reference points measured in
which type of unit?

A

volts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

The basic law for current is a series circuit states that amperage is______ parts of the circuit.

A

the same in all

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Operation of the potential relay is based on which of these principles?

A

motor develop counter EMF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q
  1. Since checking will be done with live circuits, the service technician must observe all the necessary
    precautions to avoid danger of
A

electric shock and damage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Which of these is the type of electrical diagram most commonly used for understanding sequence of operation for HVACR equipment?

A

schematic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How many BTU’s per hour will be provided by one watt of electrical energy in a resistance heater.

A

3.413

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Starting relays are NOT used by which of the following motors?

A

PSC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

When two run capacitors having values of 15 MFD and 10 MFD are connected in parallel, what is the combined value?

A

25 MFD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

If a split phase motor turns in the wrong direction, its direction of rotation can be reversed by this action.

A

interchanging the starting winding leads

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Why is it necessary to use a static wrap when replacing circuit boards?

A

to prevent component damage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Which tool is used to diagnose a de-energized circuit board?

A

ohmmeter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Under which of the following conditions should you NOT use a megger?

A

within a deep vacuum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Which of these is the correct range that should be used on a multimeter when checking current?

A

a high range to start, then working down

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Which of the following instruments is used to simulate the analog input to a variable frequency drive?

A

signal generator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Which of the following is NOT an advantage of variable frequency drives?

A

low initial equipment costs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

On a variable air volume system, if the static pressure goes up, the VFD should

A

ramp down

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

When will an overload contact on a motor starter open?

A

when excessive current flows thru the motor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Which is a difference between a motor starter and a contactor?

A

a starter has overload protection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

A full voltage starter energizes which of these?

A

all contactors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Which of these should the contactor have when only one of the contactors on a control panel can be closed at a time?

A

mechanical interlock

42
Q

Which of these is TRUE of contactors?

A

they are similar to relays

43
Q

Which of these acronyms will be found on the label of a three phase contactor?

A

TPST

44
Q

For which purpose is a time delay relay used.

A

to prevent the compressor from short cycling

45
Q

While troubleshooting, it is found that on a call for cooling, the voltage across a potential relay’s contacts remains 0 volts. the compressor then cycles on its internal overload. which of the following is a possible explanation?

A

closed contacts in the potential relay

46
Q

When the motor of a two-wire spring return actuator is operating, what is happening with the spring?

A

it is being wound up

47
Q

During flow switch installation the paddle must be

A

fitted to the pipe

48
Q

Which of the following instruments is used to verify water flow across the chiller barrel?

A

differential pressure switch

49
Q

A thermistor has a wide change in resistance for a small change in which of the following?

A

temperature

50
Q

Outdoor reset of hot water temperature for heating results in which of the following?

A

hottest water during the coldest weather

51
Q

A boourdon tube pressure gauge reads 145 psig. if local atmospheric pressure is 14.5 psia what is the
absolute pressure indicated by the gauge?

A

159.5

145+14.7psia

52
Q

Which of the following devices changes energy from one form to another?

A

transducer

53
Q

Where is a bellows used?

A

in both pressure and temperature controllers

54
Q

a photo detector converts light to a

A

electrical signal

55
Q

To lessen short cycling, which of the following adjustments could be made to the pressure control?

A

widen the differential

56
Q

Oil failure safety switches, refrigerant dual pressure switches, and overload relays in motor starters are classified as which type of controls?

A

safety controls

57
Q

For which purpose are lockout relays used in air conditioning systems?

A

prevent compressor short cycling

58
Q

Which is the proper switch to use to make the pneumatic thermostat on an air conditioning system turn the fan motor on and off?

A

P-E

59
Q

Which of the following is an analog input?

A

temperature sensor

60
Q

Which of the following is an analog output?

A

VFD speed control

61
Q

What is the desired value of a controlled variable called?

A

setpoint

62
Q

Which of these are two basic types of low water cutoff controls?

A

float type and electric probe type

63
Q

An increase in the latent load across an evaporator will cause which of the following changes in the suction
and discharge pressure?

A

there will be an increase in suction and discharge pressure

64
Q

Saturated liquid line pressure minus liquid line temperature is equal to which of these?

A

subcooling

65
Q

Low superheat or a liquid floodback to the compressor could be caused by all EXCEPT which of the following?

A

undercharged system

66
Q

Which of these reflects the temperature and the state of the refrigerant leaving the compressor?

A

hot vapor

67
Q

Which of these results can be expected if too much refrigerant is being fed to the evaporator?

A

the superheat will be low

68
Q

Which of the following gasses must never be used to pressureize or leak test a refrigeration system?

A

oxygen

69
Q

Which of the following gasses must never be used to pressurize or leak test a refrigeration system?

A

30%

70
Q

What is the purpose of using a Nitrogen purge when repairing a leak?

A

prevent copper oxide from forming inside pipe

71
Q

Which is the most accurate tool to use when measuring evacuation levels?

A

micron gauge

72
Q

Which of the following is NOT a way to speed up evacuation?

A

smaller gauge hoses

73
Q

During a standing vacuum test, the system goes from 500 microns to 2,000 microns and ten stops. Which of the following is the most likely cause?
a. leak in the system

A

moisture in the system

74
Q

Which is the issue that brought about the CFC venting laws?

A

reduction of the Ozone layer

75
Q

How many pounds of refrigerant can a recovery cylinder safely hold if the following is stamped on the side
of the cylinder?
TW = 18.2 lbs WC = 47 lbs

A

37.5lbs

76
Q

Which is the fastest way to totally recover refrigerant?

A

push pull method

77
Q

Bubbles in a refrigerant sight glass are an indication of what condition?

A

there is vapor mixed with the liquid

78
Q

When calculating subcooling for an HFC refrigerant with a large temperature glide, which column on the pressure/temperature chart is used?

A

bubble point

79
Q

For systems that use capillary tube for metering devices, which of the following is the best method for checking proper refrigerant charge?

A

superheat

80
Q

For a compressor having a lubricating oil pump, the net oil_pressure is equal to pressure.

A

oil pump discharge pressure minus compressor suction

81
Q

Discoloration of a compressors valve plate and/or valves may indicate which of these conditions?

A

contamination or overheating

82
Q

Refrigerant is compressed through a scroll compressor from the of the scroll(s)

A

outside to the center

83
Q

What is the purpose of a slide valve on a helical rotary screw compressor?

A

to provide capacity control

84
Q

Evaporator approach on a centrifugal water chiller is determined by calculating the difference between

A

entering and leaving evaporator water temperature

85
Q

In the hot as bypass control method, which system component is bypassed?

A

condenser

86
Q

In addition to evaporator pressure, the thermostatic expansion valve has which two operating pressures?

A

spring and bulb pressure

87
Q

Where is the expansion valve located in the refrigeration system?

A

in the liquid line at the entrance to the evaporator

88
Q

If the thermal bulb on the TEV comes loos from its mounting at the outlet of the evaporate, which of the following will occur?

A

the valve will open, feeding more refrigerant into the evaporator

89
Q

What is the acceptable temperature drop across a liquid line filter drier?

A

less than 2 degrees/0

90
Q

The amount of heat rejected by the condenser of an air conditioning system is typically______ the amount of heat absorbed in the systems evaporator.

A

25%

91
Q

Which solution should be used for chemically cleaning a condenser?

A

an inhibited acid

92
Q

The amount of heat removed by evaporating one pound of water in an evaporative cooling tower is approximately how many Btu(s)?

A

1000

93
Q

On a mechanical draft cooling tower, what dictates the coldest basin water temperature available?

A

outdoor wetbulb

94
Q

Which of the following does NOT need to be considered when converting from a HCFC to a HFC refrigerant in a system?

A

thickness of the line tubing

95
Q

An acid test kit is used to test the acidity of which of the following?

A

oil

96
Q

Which of the following is a disadvantage of a VRF system?

A

does not allow for future expansion

97
Q

Which is true of the heating capacity of and air to air heat pump

A

it decreases as outdoor air gets colder

98
Q

On an intermittent pilot system, when is the pilot light on?

A

through the main flame cycle

99
Q

The purpose of combustion testing is to perform all except which of the following?

A

condition air through the air handler

100
Q

Which of the following would cause continuous addition of makeup water to a radiant heating system?

A

leak in system

UA HVAC Star Exam Prep (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions