HVAC Flashcards
(257 cards)
1
Q
What type of charge does an electron have? A. positive B. Negeative C. Neutral D. Negative- positive
A
B
2
Q
If five electrons combine with three protons, the net charge will be A. negative B. positive C. zero D. neutral
A
A
3
Q
what part of an atom moves from one atom to another? A. proton B. Neutron C. electron D. molecule
A
C
4
Q
Typical insulations are A. copper, silver, gold B. steel, bronze, brass C. glass, rubber, plastic D. aluminum, nickel, magnesium
A
C
5
Q
The ampere is
A. the difference in potential between two charges
B. a measure of the quantity of electrons flowing past a point in the ectrical circuit in a given time
C. the unit of measure for resistance
D. the unit of measure for capacitance
A
B
6
Q
If two light bulbs are wired in series and one bulb burns out, the other bulb will A. go out B. stay on C. stay on, but it will be dimmer D. stay on, but it will be brighter
A
A
7
Q
what happens to the currnt in a circuit if the resistance is increased A. the current remains the same B . the current increases C. the current decreases D. this cannot be determined
A
c
7
Q
what happens to the currnt in a circuit if the resistance is increased A. the current remains the same B . the current increases C. the current decreases D. this cannot be determined
A
c
8
Q
An element in an electric heating unit is connected to a 232-V power supply. The current flow through the element is 19 A. What is the resistance of the element? A. 8 B.10 C.12 D.14
A
c
9
Q
As loads are added ina parrallel circuit, the total resistance of the circuit. A. will increase B. will decrease C. will remain the same D. cannot be determined
A
B
10
Q
To find the watts of electrical power in an electrical ciriuit, you multiply \_\_\_\_\_ together. A. ohms and amperes B. ohms and volts C. volts and amperes D. volts, amperes, and ohms
A
C
11
Q
If a conductor carrying electrical current is formed into a coil, the magnetic field around the wire will. A. cancel out B. increase C. decrease D. remain the same
A
B
12
Q
T/F Ohmmeters are to be used only on circuits that are de-energized.
A
T
13
Q
T/F In a circuit with two or more ressistance in series, the total resistance in the circuit is the sum of the resistance.
A
T
14
Q
T/F IF three bulbs are wired in parrallel and one bulb burns out, the total current of the circuit will decrease.
A
T
15
Q
T/F In a circuit with two or more resistance in parallel, the total resistance in the circuit is the sum of the resistance in the circuit.
A
F
16
Q
T/F When calculating the total resistance of a parallel circuit, the result will always be lower than the lowest resistance.
A
T
17
Q
T/F One kilowatt of electrical energy is equal to 1,000,000 watts.
A
F
18
Q
T/F IF a conductor carrying electrical current is formed into a coil, the strength of the magnetic field generated by the wire wil increase.
A
T
19
Q
T/F The unit of measurement for the charge a capacitor can store is called a Joule.
A
F
20
Q
T/ F As the diameter of a wire increases, its resistance will also increase.
A
F
21
Q
T/F Copper wire size are measured in circular mills.
A
T
22
Q
T/F The main purpose of a rectifier is to convert direct current (DC) to alternating current (AC).
A
F
23
Q
T/F A PTC thermistor causes the resistance of the thermistor to increase when its temperture rises.
A
T
24
T/F A single diode can be connected as a full wave rectifier.
F
25
T/F When checking a diode with an ohmmneter and the meter shows a resistance, if the merer leads are reversed, it should show infinity.
T
26
T/F A heat sink is a device to improve the purity of the electrons in an electrical circuit.
F
27
A good conductor of electricty has few ___________ electrons, which cna move easily from one atom to another.
Valence
28
The unit of meausure for the current flow of electrical energery is the
__________.
Ampere
29
The unit of measure for the electrical pressure forcing electrical energy through a conductor is the __________.
volts
30
_____________ are used to measure the intensity of current flow in a circuit or a particalar brach in a circuit, so they are wired in series with the circuit being evaluated.
Ammeres
31
The unit of measure for resistance is the ________.
ohms
32
If there was a current flow of 6 A in a 120 V circuit, the resistance of thee circuit would be _______ ohms.
20
33
A transformer has 10,000 turns of wire in the secondary and 100 turns in the primary. The transformer is connected to a line voltage of 120 V. The output voltage will be ________ volts.
12,000
34
A solid state device that allows electrical energy to flow through in only one direction is called ________.
rectifer or diode
35
The automatic control of a system is inteneded to
A. maintain the working conditions of the equipment with a controllable device
B. evalute overloading situations
C. maintain stable or constant condtions without excessive human interference
D. maintain safe operations for service technicatians
C
36
```
Modulating controls are used to
A. start motors
B. stop motors
C. vary the speed of a motor
D. stop the flow of a liquid
```
C
37
```
When a control is required to control space or product temperture, it is called a
A. safety device
B. thermostat
C. pressure control
D. speed control
```
B
38
```
A thermal system overload may occur if a specific electriacl or mechanical component is not cooled properly, resulting in
A. underload
B. failure
C. stagnation pressure
D. overheating
```
D
39
```
Devices, such as thermoostats, that open and close their contacts during the _____ operation of the system are refferred to as operational controls.
A. Normal
B. Initial
C. Most recent
D. Final
```
A
40
```
THe compressor in the refregerator has a protective device that keeps it from overloading and damaging itself. This device is called a
A. overload
B. capacitor
C. mass control
D. speed control
```
A
41
```
The metals most often used in a bimetal temperture controls are
A. copper and brass
B. copper and steel
C. brass and steel
D. brass and aluminum
```
C
42
```
An example of a bimetal device is a
A. snap-disc
B. mercury-filled tube and diaphragm
C. thermistor
D. bordom tube
```
A
43
The bourdom tube
A. strightens out with an increase in voltage
B. curls inward with an increase in vapor pressure
C. strighterns out with an increase in electrical current
D. strighten out with an increase in vapor pressure
D
44
```
A thermocouple is a device that
A. converts heat to mechanicla movement
B. converts heat to fluid flow
C. converts heat to electrical energy
D. couples two temperture controls together
```
C
45
T/F Brass and steel have a different rate of expanstion and contraction when heated or cooled.
T
46
T/F Fluid expansion is a way to sinse temperture change.
T
47
T/F Bellows are normally used with a vapor instead of a liquid inside it.
T
48
T/F A properly operating thermocouple connected to a solenoid in a gas valve should put out 20 to 30 millivolts.
T
49
T/F A thermistor is a device that producesa voltage across the hot and cold juctions when heated.
F
50
The most popular typw of element used for a temperature control of a gas hot water heater is rod and _________.
Tube
51
Thin metal mebrane that can operate controls based on the pressure exerted on it
diaphragm
52
Based on the concept that different metals will react differently to heat causing currnet to flow
thermocouple
53
Bimetal device used to sense water heater temperatures
rod and tube
54
A higher output thermocouple
thermopile
55
Device whose resistance changes with respect to temperture, used to control electronic circuits
thermistor
56
Two unlike metaals conncted back to back
bimetal strip
57
The purpose of a heat anticipator is to
A. anticipate a sudden rise in temperture
B. keep the thermostat warm
C. reduce the temperture swing of a conditioned space
D. ensure that the system transformer does not overload
C
58
```
The difference between system overshoot and system lag is called
A. room temperture
B. temperature rise
C. temperature swing
D. room swing
```
C
59
What is meant by the term "detent"?
A. slow motion of a contact to ensure electrical contact
B. rapid making and breaking of a contact
C. the compenation furnished by heaters in the thermostat
D. the control of the blower in the air handler
B
60
```
The heat anticipator in the thermmostat control circuits in the hrating mode is active when the
A. heating contact is open
B. heating resistor is closed
C. fan switch is open
D. fan swich is closed
```
B
61
```
The heater in the thermostat control circuit in the cooling mode is active when the
A. cooling contact is open
B. cooling contat is closed
C. fan switch is open
D. fan swich is closed
```
A
62
```
To properly set the heat anticipator, the ____ must determine what the cuurent flow is through the heating control circuit when the furnace is operating in a steady state condition.
A. manufacturer
B. homeowner
C. electrician
D. heating technication
```
D
63
```
The cold anticipator is wired in ______ with the mercury bulb cooling contacts and is energized during the off cycle.
A. parallel
B. series
C. sequence
D. oppostion
```
A
64
```
Line voltage thermostats habe heavier contacts and use which type of sensing element
A. bimetal
B. bellow
C. remote bulb
D. all of the above
```
D
65
To obtain an accurate reading of a fluid in a large pipe, a technican should
A. strap a dial-type pocket thermometer to the pipe
B. ise a digital thermometer in a glass of ice water
C. use a permanenty mounted thermometer in a well
D. any of the above will work fine
c
66
Al low pressure control has a high event and differential setting. The technician wants the system to turn on at 28 psig and shut down at 2 psig. What would be the proper settings?
A. high event: 28 psig, differential: 2 psig
B. high event: 2 psig, differential: 2 psig
C. high event: 28 psig, differential: 26 psig
D. high event: 2 psig, differential: 28 psig
C
67
```
If the suction pressure of a system is 60 psig and the oil pump is 85 psig, what is the net oil pressure?
A. 60 psig
B. 25 psig
C. 85 psig.
D. 145 psig
```
B
68
Oil pressure safty controls measure the difference in pressure to establish
A. the compressor is running
B. the oil pump is runing
C. that negative oil pressure is present
D. that posistive oil pressure is present
D
69
```
To prove that the combustion blower motor is operating before igntion, a ___ would be used.
A. toggle switch
B. pressure differential
C. push button switch
D. sail switch
```
B or D
70
```
To control ice build-up on a heat pump outdoor coil in the heating cycle , a ____ is attached to a large diaphragm.
A. toggle switch
B. micro- switch
C. push button switch
D. sail switch
```
B
71
Where would a water regulating valve that is controlling head pressure be installed?
A. water circuit at inlet of condenser
B. discharge line at outlet of compreesor
C. suction line
D. liquid line close to the condenser
A
72
```
When a water regulating valve is used to control the head pressure of a water-cooled system, the valve's spring is acting againsr which pressure to modulate the water flow?
A. head pressure of the system
B. water pressure
C. suction pressure
D. atmospheric pressure
```
A
73
T/F The heat antipipator in a thermostat prevents the temperture in the conditioned space from rising above the thermostat setting.
T
74
T/F The cold anticipator stars the cooling system early to allow the air-conditoned system to get up to capacity when needed.
T
75
T/F The advantage of using a thermistor-type thermometer over mercury-filled thermometer for measring refrigerant line temperture is that the themistor-type does not have to be insulated.
F
76
T/F A helix coil is used in some applications to sense temperture in a moving air stream.
T
77
T/F A dual pressure control is actually a low pressure control and high pressure control connected in parallel with each other.
F
78
T/F Many natural gas fired heating units operate at a maniflod pressure of 3.5 in W.C
T
79
```
A control can be which of the following?
A. electrical
B. mechanical
C. electrical and mechanical
D. all the above
```
D
80
An example of a power consuming device would be a _______ while an example of a non-consuming device would be a
A. single-pole single-throw switch, light bulb
B. light bulb, electric motor
C. electric motor, light bulb
D. light bulb, single throw single pole switch
D
81
An electrical power consuming component
A. is normally wired in series in an electriacal circiut
B. is normally used to pass power to another component
C. is often a basic switch
D. is also known as a load
D
82
```
The line side of a switch is the
A. side the load is connected to
B. neutral side of the circuit
C. side the power source is connected to
D. side with the white wire
```
C
83
```
If an air conditioning system is calling and the compressor is running but the indoor ( evaporator) fan is not running, which terminal on the thermostat will the technician most likely check first?
A. G
B.R
C.Y
D.W
```
A
84
```
The ______ is nothing more than a set of switches.
A. transformer
B. coil
C. motor.
D. thermostat
```
D
85
```
The continuity through a heat relay is checked used a
A. ohmmeter
B. voltmeter
C. clamp-on ammeter
D. micron gauge
```
A
86
```
A 10-wrap amoerage multiplier is used with an
A. voltmeter
B. clamp-on ammeter
C. ohmmeter
D. megger
```
B
87
```
Transformers are rated using
A. volt-amperes
B. volt-ohms
C. amperes-ohms
D. volt-resistance
```
A
88
```
A _____ is the easiest diagram to use to follow a circuit. This diagram normally can be studied briefly, and the circuit function should become obvious.
A. pictorial diagram
B. ladder diagram
C. layout
D. oblique drawing
```
B
89
```
AN electrical diagram showing the approximate location of the components is called a
A. pictrial diagram
B. ladder diagram
C. layout
D. oblique drawing
```
A
90
T/F If line one of a circuit had a potential of 120 V and line two was neutral, the potential voltage (difference) between line one and two would be zero volts.
F
91
T/F The heat anticipator in a thermostat is usually an adjustable type.
T
92
T/F The cooling anticipator in a thermostat is usually an adjustable type.
F
93
T/F When checking thermostat circuits, an insulted jumper wire is a handy tool.
T
94
T/F When conditions are correct, the rheostat will pass power through the device onto the system components to be controlled.
F
95
T/F While troubleshooting a 24 V control circuit consisting of a thermostat, a pressure control, and a contactor coil, the technicain reads 24 V across the thermostat, 0 V across the pressure control, and 0 volts across the contactor coil. The technician makes the follwing statement. The following statements are all considered to be true.
A. the transformer is burned out
B. the thermostat is open
C. the contactor coil is energized
F
96
T/F A 120-V/24-V control tansformer has a VA rating of 20. The maximum amperage the transformer will put out is 0.8 amps.
T
97
T/F When using a ten-wrap multiplier, the reading on the meter must be multiplied by ten.
F
98
How is the cooling anticipator normally wired to the cooling contacts?
parallel
99
How is the heat anticipator normally wired to the hrating contacts?
series
100
In a residentail air conditioning system, how are the outdoor fan and compressor wired with respect to each other?
parellel
101
In a high voltage circuit, if the fan motor a power-passing or power- consuming device?
Power-consuming
102
Explain how to read very low current in a control circuit using a clamp-on amp meter.
Wrap the wire 10 times around the clamp and then divide by 10
103
What is the amperage capacity of a 240-V/24-V control transormer with a 40 VA rating?
1.66
104
```
A _____ reacts to stop, start, or modulate the flow of water, air, or refrigerant to the system or conditioned space.
A. sensor
B. controller
C. controlled device
D. none of the above
```
C
105
```
All control systems can be subdivied into ________, no matter how many control there are.
A. throttle loops
B. control loops
C. control segments
D. sensor segments
```
B
106
```
_________ control systems were used before electronics.
A. pneumatic
B. manual
C. digital
D. mechanical
```
A
107
```
Pneumatic controls must have a permanent air supply that is ____
A. clean and moist
B. clean and warm
C. warm and dry
D. clean and dry
```
D
108
```
Most system compressor provide _______ psig of air pressure to the storage tank.
A. 90 to 100
B. 90 to 125
C. 100 to 125
D. 100 to 150
```
C
109
```
In most system compressors, the compressors are controlled with the
A. pressure switch
B. heat switch
C. limiter
D. governor
```
A
110
```
A ______ is either in the pressure reducer or in the downstream side of the system to ensure that the control air pressure does not exceed about 30 psig.
A. blowback valve
B. relief valve
C. pulldown valve
D. pressure valve
```
B
111
```
In a _____ loop, all changes happen within the loop.
A. open
B. modified- closed
C. modified-open
D. closed
```
D
112
```
A device called a _______ is used to control the large volume of air in a air conditioning systems.
A.pilot lockout
B. pilot positioner
C. pilot fixator
D. pilot engagement
```
B
113
```
The pilot positioner has a main air supply that is governed by the _______.
A. internal switch
B. internal lockout
C. internal diaphragm
D. pilot engagemnet
```
C
114
```
Controlling the water flow to the room's needs is called
A. modulating flow
B. regulating flow
C. operating flow
D. systemic flow
```
A
115
```
The temperture in the room is known as the ____ air temperture.
A. causal
B. associated
C. variable
D.ambient
```
D
116
```
Electronic controls are commonly called
A. dicrete digital controls
B. direct analog
C. direct digital controls
D. discreate event controls
```
C
117
```
The controlled envirornment could be controlled by an arry of ____ such as dampers, fans, vairble-frequency drives.
A. direct digital controls
B. controlled output devices
C. controlled input devices
D. operational devices
```
B
118
```
________, usually housed internally inside the controller, convert the information form either analog to digital (A/D) or digital to anlog (D/A) format.
A. signal converters
B. transceivers
C. signal processors
D. signal managers
```
A
119
T/F The very first control systems were used to start and stop the various components.
T
120
T/F Space temperture is the only temperture that is important in modern systems.
F
121
T/F Modern controls systems only have on-off control capability.
F
122
T/F Today control outputs devices can receive signals as either analog or digital.
T
123
T/F Controllers are devices that can measure some type of environmentall parameter or a controller variable and convert this parameter to a value that the controller can understand.
F
124
T/F DDC is a control process in which a microprocessor, acting as a digital controller, constantly updates a database of internal information.
T
125
In a home air-conditioning system, the ________ is the sensor.
Thermostat
126
The _______ system actually chages or conditons a signal in three steps.
DDC
127
__________ send information back to the controller in terms of resistance (ohms).
passive sensors
128
_________ sends information back to the controller in terms of milliamps (mA) or volts.
Active sensors
129
```
A motor's speed is determined by
A. size
B.voltage
C. amperage
D. number of motor poles
```
D
130
```
Start windings are placed ________ with the run windings.
A. 180 degrees out of phase
B. in phase
C. slightly out of phase
D. in series
```
C
131
The start windings have
A. fewer turns than the run windings
B. more turns than the run windings
C. the same number of turns as the run windings
D. larger diamter wire than the run winding
B
132
```
A spilt-phase has a _____ winding and a ____ winding.
A. start,run
B. start, common
C. common, run
D. run, common
```
A
133
```
When a general duty spilt-phase motor reaches approximately 75% of its operating speed, the start winding is de-energized by a
A. circuit board
B. capacitor
C. centrifugal switch
D. dual voltage switch
```
C
134
```
A split-phase motor that has a current relay and a start cappacitor is called a ______ motor.
A. capacitor start, capacitor run
B. capacitor start, induction run
C. induction start, induction run
D. permanent split capacitor
```
B
135
```
When a capacitor start induction run motor is runing and up to speed, what is the total capacitance acting on the motr? ( Assume the run capaciotor is 5 microfarads and the start capacitor is 20 microfarards, if present)
A. 4 microfarads
B. 5 microfarads
C. 20 microfarads
D. 25 microfarads
```
B
136
```
A permanent split capacitor motor that is running and up to speed will have the start winding
A. energized
B. de-energized
C. in series with the run winding
D. removed from the circuit
```
a
137
```
When a capacitor start, capacitor run motor initially starts, what is the total capacitance acting on the motor?( Assume the run capacitor is 5 microfarads and the start capacitor is 20 microfarads, if present)
A. 4 microfarads
B. 5 microfarads
C. 20 microfarads
D. 25 microfarads
```
D
138
Capacitors wired in series with the starting winding provide
A. longer starting time
B. greater starting torque
C. aid in starting three pahse motors
D. more efficient operation at full load speed
B
139
The shaded pole motor
A. has little starting toque
B. has excessive starting torque
C. has greater efficiency than most split-phase motors
D. will start against a heavy starting torque
A
140
Three phase motors have
A. three start and three run windings for each phase
B. one start and one run winding for each phase
C. run windings only
D. a start switch in each phase circuit
C
141
```
A current magnetic relay opens and closes its contacts based on the
A. current in the start windings
B. voltage across the start winding
C. voltage across the run winding
D. current in the run winding
```
D
142
```
The starting device usually used on single pahse, fractional horsepower motors requiring low starting torque is the
A. potential relay
B. current relay
C. centrifugal switch
D. differentail relay
```
B
143
```
The posistive temperture coefficient resistor start device is a type of
A. capacitor
B. variable resistor
C. switching device
D. diode
```
B
144
```
A permanent split-capacitor motor has a
A. start and run capaciotor
B. start capacitor only
C. run capacitor only
D. spilt pahse capacitor
```
C
145
T/F The magnetic fields generated in the rotor and stator of a motor causes thee rotor to be pushed around the shaft.
F
146
T/F The heavier the laod on an operating motor, the greater the amount of slip.
T
147
T/F In order to change the direction of rotation of a spilt-phase motor, the technician must change the direction of current flow throuhg the start winding.
T
148
T/F The centrifugal switch mounted on the shaft of a split-phase motor has a normally closed contact.
T
149
T/F The contacts in a potential type starting relay are normally closed.
T
150
T/F Once the start winding and the start capacitor have been removed for the circuit, the motor will continue to operate with only the run winding energized.
T
151
T/F The microfared rating of the run capaciotor is much lower than that of the start capacitor for ant given motor application.
T
152
T/F A capacitor start capaciotor run motor that is wired with a potential relay will have the start winding energized when the relay's contacts open.
T
153
T/F The contacts in a current type starting relay are normally closed
F
154
T/F The resistances of the windings in a three phase motor are all equal.
T
155
The _______ is a winding that, when energized, will generate a magnetic field as there will be curent flowing through it.
stator
156
The rotating portion of an electric motor is called the _________.
rotor
157
A motor that has copper bars in the rotor is classified as a _________ type.
squial cage
158
On a potential relay, the coil is connected between terminals 2 and _______.
5
159
```
Which of the follwing voltage are not safe for a 208 V motor to operate?
A. 170V
B.220V
C.238V
D.both a and c
```
D
160
```
If the voltage supplied to the motor is well below the motor rated voltage, the current draw will be ______ it should be.
A. lower than
B. the same as
C.higher than
D. in reverse polarity than
```
C
161
```
The voltage tolerance of a standard electric motor is
A. +5% -10%
B.+10% -5%
C.+10% -10%
D.+15% -15%
```
C
162
```
The locked-rotor amperage is normally _______ times as great as the run-load amperage.
A. two
B.three
C.five
D.ten
```
C
163
```
Why are explosion-proof motors not normally used on standard equipment?
A. they are too large
B. they are too noisy
C. they are to expensive
D. they cannot be replaced
```
c
164
```
The motor that should be used in a potentially wet are is a _____ motr.
A. enclosed
B. drip proof
C. explosion proof
D.open
```
B
165
When refering to motors, to what does the "insulation class" relate?
A. the noise level of the motor
B. the type of base on which the motor is mounted
C. the normal operating temperature of the motor
D. both a and b
C
166
A sleeve bearing would typically be used in a motor that operates with a
A. light load and where noise is a factor
B. heavy load and where noise is a factor
C. heavy laod in a atmosphere
D. heavy laod in a moist atmosphere
A
167
```
A slotted screw at the bottom of the bearing housing is called a
A. drain plug
B. purge srew
C. relief plug
D. retaining screw
```
c
168
```
A direct-drive motor is usually connected to a load with a
A. cradle mount
B. rigid base mount
C. pulley
D. coupling
```
D
169
Grounding straps are required on resilient mounted motors to
A. prevent rotation of the motor in the mount
B. help reduce motor vibration transfer to the object on which the motor is mounted
C. ground the motor in case of winding failure
D.act as the position for locating the motor leads
c
170
```
The width of a drive belt is classified as
A. large or small
B. narrow or wide
C. A or B
D. 1 or 2
```
C
171
```
The alignment of a motor and the driven mechanism must be done at room temperture and
A. after heating with a torch
B. at operating temperature
C. after running for one minute
D. again after several days of operation
```
B
172
T/F A motor can burn out if the supply voltage is either too high or too low.
T
173
T/F One method a technicain can employ to check a motor is to take amoerage readings of a motor( both on start-up and after start-up) and compare them to the motor's namplate
T
174
T/F The delta transformer has been popular in some locations in the past.
T
175
T/F A drip-proof motor is designed to prevent any lubricating oil from leaving any of the bearings.
F
176
T/F When oiling a permanently lubricated motor, a 20-weight, non-detergent motor oil should be used.
F
177
T/F Regardless of the type of motor or application, the motor bearings require yearly lubrication.
F
178
T/F There is a definte relationship between the speed of the motor and the speed of the blower.
T
179
The alternating current frequency supplied by the power companies in the United States is __________ hertz.
60
180
If the applied voltage is too high, the motor may develop hot spots within its windings, but it will not always experience ___________.
high amperage
181
The vertical condenser fan is trying to fly downward into the unit to push air out the top, which puts a real load on the end of the bearing, caled the __________ surface.
thrust
182
In order to be electrically safe, a motor that is set in a resilient mount must have a __________.
ground strap
183
Whenever possible, when changing a motor, the ______ should be obtained.
exact replacement
184
The device that transfer the motor's energy to the driven component is called the ________.
coupling
185
A common practice in condensing units is to use a contractor with only one set of controls opening only one side of the power to the unit. This is called
A. reduce the cost of the contactor
B. make it easier to wire the unit
C. teach the service technician not to put hands in the unit with the power on
D. provide off-cycle heat to the compressor
D
186
Beside maintaining pressure on the contacts for current carrying capacity, the pressure springs have a second important function.
A. keep the contacts in line
B. help obtain equal contacts against the stationary contacts
C. slow down the pull of the armature into place to reduce the noise
D. increase the power requird to close the contacts
B
187
```
When a contator's coil is energized, how much resistance should be measured between terminal L1 and terminal T1
A. zero ohms
B. 50-3000 ohms
C. 5000-6000 ohms
D.infinite
```
A
188
Technician A says that if you take a voltage reading from terminal L1 to terminal T1 on a contactor whose coil is energized, you should read zero volts. Technician B says that contactors can only have normally open contacts. Which of the follwing statements is correct?
A. technician A is correct. Technican B is correct
B. A correct. B incorrect
C. A incorrect.B correct
D. A incorrect. B incorrect
B
189
```
An inherent motor protector is a
A. circuit breaker
B. motor starter overload
C thermally activated device in the motor winding
D. line fuse
```
C
190
The service factor of an electric motor is determined by
A. National Elctrical Code
B. Natinal Electrical Manufacturers Association code
C. motor's reserve capacity
D. the required wire size supplying power to the motor
C
191
Standards for motr overload protection are set by the
A. United States Department of Transportaion
B. National Electrical Code
C. Environmental Protection Agency
D. American National Standards Institute
B
192
```
A solder pot is part of a
A one time fuse
B. resettable circuit breaker
C. time-delay fuse
D. plumbers tool kit
```
B
193
```
Which of the following overload devices is not affected by ambient temperature?
A. solder pot
B. magnetic
C. bimetal
D. time-delay fuse
```
B
194
Most electrical problems with an electric motors are
A. short circuited windings, closed windings , and grounded windings
B. short circuited windings, open windings, and grounded windings
C. all of the above
D. none of the above
B
195
A technicain needs to check a single-phase compressor. He labels the three terminals A , B and C and takes resistance readings of the winds. HE reads 10 ohms from A to B infinity from B to C and infinty from C to A.
A. a: common b:start c: run
B. cannot identify terminals:windings grounded
C. a: start b: run c: common
D. cannot identify terminal: open windings
D
196
```
Technican A says that while checking the windings of a compressor, a reading of 10 ohms or less from the common terminal to ground indicates that the motor is okay. Technicain B says that the resistance of the star winding should always be less than the resistance of the run winding. Which of the following statements is correct.
A. A is correct. B incorrect
B. A correct. B incorrect
C.. A incorrect. B correct
D. A incorrect. B incorrect
```
D
197
An open winding in an electric motor means that
A. the winding is making contact with the motor frame
B. one winding is making contact with another winding
C. a wire in a winding is broken
D. the centrifugal switch to the start winding is open
c
198
```
Technicain A says that a shorted winding will result in an increased current flow through the winding. Technician B says that if a motor is to be replaced, a motor with a lower horsepower rating should always be used. Which of the follwing statement is correct.
A. a is correct. b is correct
B. a is correct. b is incorrect
C. a is incorrect. b is correct
D. a is incorrect. b is incorrect
```
B
199
If the resistance of the run winding decreases, the
A. motor probably will not start
B. motor will draw too much current while it is running
C. centrifugal starting switch will not start the motor
D. load on the motr is probably too great
B
200
If a condenser fan motor grounds out, it will usually
A. trip a circuit breaker to shut off the unit
B. keep running as the current is only going to ground
C. run a little faster because the amperage draw will increase
D. cause the evaporator to ice up
A
201
A megger
A. is an ammeter that can measure very small amounts of current
B. is a digital voltmeter that measures very high resistances
C. measures high voltage direct current
D. measures very high resistances
D
202
```
If a motor hums but does not start, there is a potential problem
A. with the starting components
B. with an open winding
C. with insufficient supply voltage
D. all of the above
```
D
203
The recommended way to discharge a capacitor is to
A. place a screwdriver across the terminals
B. assume it will discharge itsel over a period of time
C. use a 20,000 ohm 5 watt resistor that has had insulated leads soldered to it
D. use an ohmmeter
C
204
The wiring and connectors that carry the power to a motor must be in good conditons. When a connection becomes loose, oxidation of the copper wire occurs. The oxidation
A. has no effect on the electrical connections
B. acts as an electrical resistance and causes the connection to heat more
C. decrease the resistance
D. none of the above
B
205
What is the best method to repair a fractional horsepower motor that has bad bearings.
A. replace the bearings
B. replace the bearings and shaft
C. add a capacitor to the circuit for added torque
D. replace the entire motor
D
206
T/F The locked rotor amperage, LRA of a motor is typically five times higher than the full load amperage, FLA, of the motor and can be as high as seven times the FLA.
T
207
T/F A set of contacts are closed when the relay is energized. These contacts are classifed as normally closed.
F
208
T/F Auxiliary contacts are usually rated at a lower amperage than the contactor's prmary contacts.
t
209
T/F Contactor contacts that are badly pitted can cause the motor to burn out.
T
210
T/F A sign of contact failure is discoloration on the contact surface
F
211
T/F Bimetal and solder pot overload devices are thermally operated
T
212
T/F The sun shining on a distribution panel has no effect on the breakers in the panel
F
213
T/F Magnetic overload devices are the most accurate type of device for electrical protection
T
214
T/F If the cost of repairing the motor is close to the cost of replacing the motor, it would definitely pay to repair the motor if the new component carries a one- year warrenty and the reaired motor carries only 90 day guarantee.
F
215
T/F Belt tension will not have any affect on the wear of the bearings
F
216
T/F Pulleys must be in proper alignment or belt and bearing wear will occur
T
217
T/F Open winding will not affect the resistance reading of the start winding as well as the resistance reading between the Run and Start terminals
F
218
T/F If the resistance of the run winding is lowered, the imbalance in magnetic fileds between the start and the run winding will be increased and the starting torque of the motr will actually increase.
T
219
T/F If a resilient-mounted motor develops a short to the frame, the technician can simply cut the ground strap wire as a permanent repair.
F
220
T/F Before testing a run or start capacitor with an ohmmeter, the capacitor should be discharged with a 20,000 ohm 5 watt resistor.
T
221
T/F Before testing a run or start capacitor with an ohmmeter, the capacitor should be discharged with a 20,000 ohm 5 watt resistor.
T
222
T/F The electrical components fo a fully welded hermetic compressor are checked at the disconnect box for the compressor unit
F
223
The best way to repair a defective relay is by _______.
replacement
224
The most common material used on the surface of contacts is _______.
silver
225
The best way to repair a large contactor is by the replacement of __________.
component parts
226
Two common resons for motor failure are improper pully alignment and _______.
tight belt
227
A motor has four leads out of it: two red and two black. The resistance between the red leads is 3 ohms. The resistance between the black lead is 5 ohms. The black leads are connected to the _______ winding.
start
228
A motor will not start when power is applied. If the belt is removed, the pulley spen and power applied, and the motr continues to run, the first part to check is the ______.
starting switch
229
The leads of an ohmmeter using the R 100 scale are placed on the terminals of a capacitor and then reversed. The needle does not move. This would indicate that the capaciotor is ______.
open
230
If the needle of an ohmmeter used to check a capacitor goes to the 0 ohms reading and does not move, this would indicate that the capaciotr is ______.
short
231
```
Quartz and glass panel electric units are classified as
A. naural-convection heaters
B. forced- convection heaters
C. forced- dreaft conductors
D. radiant heaters
```
D
232
```
An electric heating unit that utiltzes ductwork to distribute the heated air is classified as a
A. natural- convection heater
B. forced- convection heater
C. forced- draft conductor
D. radiant heater
```
B
233
T/f Generally speaking, electric heat is very effiecient but can be more expensive to operate compared to oil and gas
T
234
T/F Some units may be designed to move enough air across the heating elements so that they do not glow.
T
235
T/F One potential saftey hazard that all technications should be aware of when working on an electric furncae is that there are many exposed electrical connections behind th inspection panels.
T
236
T/F Electric heating units provide almost instant heat. Therefore, anticipators are not needed in electric heat thermostats.
F
237
T/F If the number two contact on a packeage sequencer fails to close, the number three contact can still close.
T
238
T/F All electric furnaces use package sequencers
F
239
If the fan were to fail and the limit switch stuck closed, the element would be cut off by the ________.
Fusiable link
240
In order to prevent a duct-mounted electric heater being energized when the fan is not on, a _______ should be used
interlock
241
A set of contacts actuated by a bimetal strip with a low- voltage wire wrapped around it is called a ___________.
sequencer
242
In order to provide time delay between stages of electric heat, the controls that are used are called ________.
sequencers
243
The benefit of electric heat baseboard heating are that
A each room can be controlled individually
B they are inexpensive to install
C they operate on a 24 V power supply
D both a and b
D
244
```
Any unit heater designed to have air forced across the element should not be operated without the
A fuse
B interlock
C element
D fan
```
D
245
Which of the following elements is not a power consuming devise?
A the sequencer heater coil
B a magnetic solenoid that moves the armature in a contractor
C the contacts of a contractor
D the blower motor
C
246
What type of control would be used to cycle compressors on and off in response to evaporator pressures that indirectly control box temperature?
Low pressure control
247
Explain why the thermistor type sensor is normally embedded in the motor windings?
The close contact with the winding give a fast and accurate response
248
What is a thermopile?
Multiple thermocouples together wire in series to make a high output voltage. It should produce about 500mv
249
Explain the difference between a positive temperature coefficient thermistor and a negative temperature coefficient thermistor.
NTC- temp increase resistance decrease
| PTC- temp increase resistance increase
250
Define bimetal strip
Brass or steel that expand and contract when they are heated or cooled
251
Why are two different metals used to produce movement in bimetal elements?
Two metals are used because they both have different rates of expansion and contraction with heat or cold
252
To make a bimetal element operate over a wide temperature range, what is done to the element?
Coiled into a circular shape it into a hairpin or wounded into a helix
253
How can pressure be used to control the temperature of refrigerated space?
A large bulb filled with volatile liquid one that boils and creates vapor pressure when heated. An increase in vapor pressure forces the diaphragm to move outward when heated and inward when cooled
254
Define a diaphragm used in controls?
It opens or closes as the temperature drops and rises
255
What is the major advantage of a remote bulb control?
They can be replaced and they are remote
256
An oil pressure safety control usually has a 90 second time delay built into it. Why?
It allows the compressor to get started and builds up the necessary oil pressure, preventing unnecessary cut outs when the oil pressure varies for only a moment
