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HVAC CDC's > Volume 3 > Flashcards

Volume 3 Flashcards

1
Q

(401) What relationship between magnetic field and conductors is required to generate voltage mechanically?
a. No relationship exists between the two.
b. Relative motion between to the two.
c. A direct temperature relationship.
d. Conductors must be solid copper.

A

b. Relative motion between to the two.

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2
Q

(401) Nickel and chromium alloys are used in heater elements because they
a. have a very low resistance to current.
b. make it possible to operate the elements at high pressures without melting.
c. make it possible to operate the elements at high temperatures without melting.
d. make it possible to operate the elements at low temperatures without melting.

A

c. make it possible to operate the elements at high temperatures without melting.

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3
Q

(401) What effect does the length of a wire have on the amount of pressure needed to force the electrons to the load device?
a. The long wire decreases need for voltage.
b. No pressure will be needed.
c. More pressure will be needed.
d. Less pressure is needed.

A

c. More pressure will be needed.

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4
Q

(401) Resistance should not be considered a bad thing because
a. even conductors offer resistance to flow.
b. a circuit reading O.L. will still allow flow.
c. voltage will always flow, no matter the resistance.
d. an open circuit will allow flow.

A

a. even conductors offer resistance to flow.

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5
Q

(401) All forms of opposition to current flow are measured in
a. amperes.
b. ohms.
c. volts.
d. watts.

A

b. ohms.

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6
Q

(401) How is direct current produced?
a. By a battery or a thermocouple.
b. Through a rotating magnetic field.
c. Through relative motion.
d. By an alternating current generator.

A

a. By a battery or a thermocouple.

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7
Q

(401) The sine wave gets its name because the alternator output voltage at any one point on the wave is the product of the sine of the
a. product of the sine of the stator angle and the peak voltage.
b. rotor angle and the frequency.
c. rotor angle and the zero voltage.
d. rotor angle and the peak voltage.

A

d. rotor angle and the peak voltage.

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8
Q

(401) What can you do to greatly increase the inductance of a coil?
a. Insert any non-magnetic substance.
b. Remove the magnetic core.
c. Add a core of magnetic material.
d. Add a core of balsa wood.

A

c. Add a core of magnetic material.

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9
Q

(401) Current lags the voltage in a purely inductive circuit because of the
a. resistance of the circuit.
b. opposition by DC voltage.
c. opposition by impedance.
d. opposition by inductive reactance.

A

d. opposition by inductive reactance.

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10
Q

(402) When working with electrical equipment, how should you treat all electrical circuits as being
a. dead.
b. live.
c. safe.
d. grounded.

A

b. live.

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11
Q

(402) How can you prevent anyone from accidentally closing the breaker to a circuit that is under repair?
a. Lock the breaker in the ON position so other people know it is on.
b. Lock the breaker in the OFF position and tell other technicians you plan on tagging it.
c. De-energize the circuit by closing the switch and post a warning sign outside of the breaker box to let other technicians know you are working there.
d. Lock the breaker in the OFF position and tag it to indicate that the system is being repaired.

A

d. Lock the breaker in the OFF position and tag it to indicate that the system is being repaired.

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12
Q

(403) If using an aluminum-clad wire in place of a copper wire, how many sizes larger must the wire be to carry the same current safely?
a. One.
b. Two.
c. Three.
d. Four.

A

a. One.

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13
Q

(403) The type of insulation for a conductor is primarily based on
a. insulation is the same for all conductors.
b. where it is going to be used.
c. the load device.
d. the line voltage.

A

b. where it is going to be used.

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14
Q

(403) What, if anything, does the location of a conductor affect?
a. Nothing, because it is insulated.
b. The device it is connected to.
c. Whether it is stranded or not.
d. Its current-carrying capacity.

A

d. Its current-carrying capacity.

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15
Q

(404) How is a solderless pigtail splice finished?
a. When applying the solder to the joint.
b. By twisting the wire into three wires.
c. With a wire nut.
d. By stripping the insulation.

A

c. With a wire nut.

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16
Q

(404) When making a terminal loop, what will happen if the loop is not placed in a clockwise direction?
a. It will never connect.
b. The screw will keep the loop tight.
c. The screw tends to spread the loop as you tighten it.
d. It will be looser than if you turn it counterclockwise.

A

c. The screw tends to spread the loop as you tighten it.

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17
Q

(404) How is a stranded wire pushed into a push in connection?
a. Insert a small screwdriver into the slot.
b. Insert a large screwdriver into the slot.
c. Pull the wire through with wire strippers.
d. Pull the wire through with needle nose pliers.

A

a. Insert a small screwdriver into the slot.

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18
Q

(404) How do you ensure the wire is placed tightly into a push-in connection?
a. By pulling slightly on it.
b. By pushing it out of the connector.
c. By pulling hard with a needle nose plier.
d. By pulling hard with a wire stripper.

A

a. By pulling slightly on it.

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19
Q

(404) When checking voltage rating, what will result if you place two hot wires to the same side of a device?
a. Proper system operation.
b. Device will explode.
c. A short to ground.
d. A direct short.

A

d. A direct short.

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20
Q

(404) What could result if a circuit is forced to carry too much current?
a. Circuit will run properly.
b. A fire or electrocution.
c. A more efficient circuit.
d. Circuit will exceed expectations.

A

b. A fire or electrocution.

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21
Q

(405) What is a common theme amongst schematics?
a. Different parts of the same component being separated.
b. Line circuit being the biggest portion of the diagram.
c. Load circuit being the biggest portion of the diagram.
d. Control circuit being the smallest portion of the diagram.

A

a. Different parts of the same component being separated.

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22
Q

(406) On the Environmental Control Unit (ECU), what component should come on after the compressor relay is energized?
a. Evaporator fan.
b. Condenser fan.
c. Compressor.
d. Lockout relay.

A

c. Compressor.

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23
Q

(406) What should you be doing as you follow each circuit on a schematic?
a. Guessing the potential solution.
b. Jumping around the schematic.
c. Simply moving your finger left to right over the diagram.
d. Describing in your head what is occurring with each component.

A

d. Describing in your head what is occurring with each component.

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24
Q

(407) What is the key to understanding complex circuits?
a. Breaking down the line circuits into smaller circuits.
b. Keeping the complex circuits as large circuits and working through each in a logical manner.
c. Breaking down the complex circuits into smaller circuits and skipping circuits you don’t understand.
d. Breaking down the complex circuits into smaller circuits and working through each in a logical manner.

A

d. Breaking down the complex circuits into smaller circuits and working through each in a logical manner.

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25
Q

(408) What are you checking for when you troubleshoot a circuit using voltage?
a. Proper resistance at one point.
b. The amperage between two points.
c. The potential difference between three points.
d. The potential difference between two points.

A

d. The potential difference between two points.

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26
Q

(408) How should you connect a voltage meter when checking AC voltage?
a. In parallel.
b. In series.
c. With one lead connected to the circuit.
d. In a way that recognizes the polarity.

A

a. In parallel.

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27
Q

(408) When testing equipment for high voltage, when should you connect your meter?
a. While the compressor is running.
b. After selecting the voltage setting.
c. Before turning on power.
d. After turning on power.

A

c. Before turning on power.

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28
Q

(408) What should you do to the multimeter before checking for ohms?
a. Turn it off and on.
b. Insert thermistor attachment.
c. Remove battery because it creates voltage.
d. Zero it out by touching the leads together.

A

d. Zero it out by touching the leads together.

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29
Q

(408) What does it mean to isolate the part of the circuit you are testing?
a. Check it with a meter.
b. Physically remove the entire component.
c. Remove the components electrical and non-electrical hardware.
d. Electrically disconnect the part being tested.

A

d. Electrically disconnect the part being tested.

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30
Q

(408) What tool should you use to test insulating material?
a. A megohmmeter.
b. A meter set to volts.
c. Clamp-on ammeter.
d. A regular meter set to ohms.

A

a. A megohmmeter.

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31
Q

(408) When taking current readings using the clamp-on ammeter, you squeeze the trigger assembly to
a. close the clamping jaws and place the open jaws around one of the circuit leads.
b. open the clamping jaws and place the open jaws around one of the circuit leads.
c. close the clamping jaws and place the jaws around two of the circuit leads.
d. to open the clamping jaws and place the open jaws around two of the circuit leads.

A

b. open the clamping jaws and place the open jaws around one of the circuit leads.

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32
Q

(408) What effect does an open circuit have on the load device? The load device will
a. run intermittently.
b. run more efficiently.
c. not operate.
d. operate continuously.

A

c. not operate.

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33
Q

(408) What should you do if you are having problems troubleshooting?
a. Ask for help.
b. Stress out.
c. Close out the job and return to the shop.
d. Stay on job site for hours even if you get nowhere.

A

a. Ask for help.

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34
Q

(408) What is the next step after a part has been replaced?
a. Close out the job.
b. Run an operational check.
c. Disconnect electrical circuit.
d. Tell your supervisor the job is complete.

A

b. Run an operational check.

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35
Q

(409) Where is a permanent distribution panel mounted?
a. At a construction site.
b. Outside of a tent in the desert.
c. At a forward operating base only.
d. In a wall or other frame structure in a facility or home.

A

d. In a wall or other frame structure in a facility or home.

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36
Q

(409) What happens to the circuit when a fuse blows?
a. It creates a short.
b. It creates an open.
c. It creates a ground.
d. It closes the circuit.

A

b. It creates an open.

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37
Q

(409) How does a magnetic-type circuit breaker open the circuit?
a. Automatically after 8 seconds.
b. Automatically after 10 seconds.
c. Through delay action.
d. Instantly.

A

d. Instantly.

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38
Q

(410) In a push-button switch, why are the push buttons insulated from the movable contact?
a. To prevent the switch from closing when it is pushed.
b. To avoid injury from electrical shock.
c. To create heat from the current.
d. To complete the circuit.

A

b. To avoid injury from electrical shock.

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39
Q

(410) How must a snap-action switch close to avoid excessive arcing?
a. Quickly or slowly.
b. Quickly.
c. Slowly.
d. Within one minute.

A

b. Quickly.

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40
Q

(411) Which coil of a transformer is always connected to the incoming power?
a. Both coils.
b. Primary coil.
c. Secondary coil.
d. The control side.

A

b. Primary coil.

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41
Q

(411) What is generated around the coil if AC flows through it?
a. Conduction.
b. Relative motion.
c. DC voltage.
d. An alternating magnetic field.

A

d. An alternating magnetic field.

42
Q

(411) What happens when an alternating magnetic field is generated by one coil and cuts through the turns of a second coil?
a. DC current will flow.
b. DC voltage is created.
c. A magnetic field stays in the primary coil.
d. A voltage is induced in the second coil.

A

d. A voltage is induced in the second coil.

43
Q

(411) What happens when 24 volts is applied to a relay coil?
a. Contacts change positions.
b. Contacts will only close.
c. Contacts will only open.
d. Contacts will maintain their position.

A

a. Contacts change positions.

44
Q

(411) What is the principal cause of a solenoids coil malfunction?
a. Excessive heat.
b. Refrigerant.
c. The armature.
d. Technician negligence.

A

a. Excessive heat.

45
Q

(412) In a split-phase motor, if the start winding is not disconnected after a short period of time, it will
a. burn up.
b. increase efficiency.
c. increase running torque.
d. open after five additional minutes.

A

a. burn up.

46
Q

(412) How does the split-phase motor operate after the start winding is removed?
a. By the rotating magnetic field produced by the run winding and endbell.
b. By the rotating magnetic field produced by the run winding and rotor.
c. By the twisting magnetic field produced by the run winding and stator.
d. By the rotating magnetic field produced by the DC sine wave.

A

b. By the rotating magnetic field produced by the run winding and rotor.

47
Q

(413) How is a toggle switch wired with the hot conductor in the circuit?
a. Wired to create an open.
b. Directly to the neutral.
c. In parallel.
d. In series.

A

d. In series.

48
Q

(413) What prevents the contactor chatter?
a. Shaded rings.
b. Solenoid.
c. Rubber gaskets.
d. Control voltage.

A

a. Shaded rings.

49
Q

(413) When replacing a heater, how are they identified?
a. Use the same one you are replacing.
b. Catalog number.
c. By size.
d. By color.

A

b. Catalog number.

50
Q

(414) The first step in removing an electric motor is to ensure the circuit breaker
a. or disconnect switch is closed.
b. is closed and the disconnect switch is open.
c. is open and the disconnect switch is closed.
d. or disconnect switch is open.

A

d. or disconnect switch is open.

51
Q

(414) When an external-drive motor starts but hums, what is the probable cause?
a. A bad capacitor or centrifugal switch.
b. A bad motor.
c. A bad stator.
d. A bad rotor.

A

a. A bad capacitor or centrifugal switch.

52
Q

(415) When troubleshooting motor failure, how do you determine if a motor is overloaded?
a. Take an ohm reading.
b. Take a megohm reading.
c. Take a current draw with an ohmmeter.
d. Perform a current draw with an ammeter.

A

d. Perform a current draw with an ammeter.

53
Q

(415) What should the motor shaft be check for when troubleshooting motor failure?
a. Depth.
b. Width.
c. Length.
d. Any up or down play.

A

d. Any up or down play.

54
Q

(415) What does a meter reading of ohms mean when checking a circuit to a grounded surface?
a. An open.
b. A ground.
c. The circuit is not grounded.
d. There is no resistance to ground.

A

b. A ground.

55
Q

(416) What could create excessive noise from the motor?
a. Rotor is aligned.
b. Motor is disconnected.
c. Belts are at proper deflection.
d. Motor not being securely mounted.

A

d. Motor not being securely mounted.

56
Q

(416) How can motor accessory noise be eliminated?
a. Placing tape over wire nuts.
b. Tightening the wire nuts.
c. Tightening the oil well cover and connection box cover.
d. Placing electrical tape over connection box.

A

c. Tightening the oil well cover and connection box cover.

57
Q

(417) When checking coupling alignment, what should you do if any part of a coupling is damaged?
a. Use coupling glue to fix it.
b. Tape it together.
c. Refurbish it.
d. Replace it.

A

d. Replace it.

58
Q

(417) How must the run windings be connected, to operate a dual-voltage motor on high voltage?
a. Directly to the transformer.
b. Directly to the thermostat.
c. In parallel.
d. In series.

A

d. In series.

59
Q

(417) How do you change the rotation of a three-phase motor?
a. Change all three power leads.
b. Change any two power leads.
c. Connect one lead to neutral.
d. Wire it for a single-phase application.

A

b. Change any two power leads.

60
Q

(418) Where are the load terminals connected in a three-phase controller?
a. T1, T2 and T3.
b. L1, L2, and L3.
c. L1 and L2.
d. T1 and, T2.

A

a. T1, T2 and T3.

61
Q

(418) What contacts must close for supply power to be sent to the load circuit?
a. The normally open main contacts.
b. The normally open line contacts.
c. The normally closed main contacts.
d. The normally closed line contacts.

A

a. The normally open main contacts.

62
Q

(419) If an air compressor runs for an extended period of time, the oil in it will
a. cool down and vaporize.
b. heat up and liquefy.
c. cool down and sludge.
d. heat up and turn into a vapor.

A

d. heat up and turn into a vapor.

63
Q

(419) When oil from an air compressor carbonizes and solidifies, what problems, if any, can it cause downstream?
a. None.
b. Line voltage issues.
c. Too large of an increase in airflow.
d. Valves and air tools to malfunction.

A

d. Valves and air tools to malfunction.

64
Q

(420) When you push the test button on the automatic drain of an air compressor, there should be a blast of air and
a. no moisture.
b. a little moisture.
c. 3 pounds of moisture.
d. 5 pounds of moisture.

A

b. a little moisture.

65
Q

(421) What happens to the vapor pressure inside a sensing bulb when the surrounding air temperature increases?
a. It leaves the bulb and capillary.
b. It explodes.
c. It decreases.
d. It increases.

A

a. It leaves the bulb and capillary.

66
Q

(422) What could occur if the system throttling range is too small?
a. Operator hunting.
b. Controller sensitivity will be adjusted.
c. Complete loss of control of the system.
d. Very efficient control of the system.

A

a. Operator hunting.

67
Q

(423) In a timed on-off control, when does the heating anticipator cause the system to turn off?
a. After the space temperature reaches set point.
b. Early before the space can overheat.
c. Two degrees above set point.
d. Ten degrees below set point.

A

b. Early before the space can overheat.

68
Q

(423) In proportional control, if the room is very cold, how much heat will the system provide?
a. One hundred percent heat every time.
b. A minimum of 35 percent heat.
c. An amount in proportion to the need.
d. An amount in proportion plus 25 percent integral action.

A

c. An amount in proportion to the need.

69
Q

(423) What is added to proportional control to correct its poor control and energy usage?
a. Timed on-off control.
b. Floating control.
c. Integral action.
d. On-off control.

A

c. Integral action.

70
Q

(424) How do valves and dampers move through their complete range of motion?
a. By on-off control.
b. By loosening the linkages.
c. By free flowing linkages.
d. By an actuator that drives them.

A

d. By an actuator that drives them.

71
Q

(425) In timed on-off control, what is the result of the controller not having to wait until it can detect change in the control variable?
a. A 25-percent increase in lag.
b. A 75-percent increase in lag.
c. The system is constantly lagging.
d. Control system lags have no significant effect.

A

d. Control system lags have no significant effect.

72
Q

(425) In floating control, how does the controller move in relation to the deviation of the controlled variable?
a. Its movement corresponds to the direction of deviation of the controlled device.
b. Its movement is the inverse to the direction of deviation of the controlled device.
c. There is very minimal relation between the controller and the controlled variable.
d. Its movement floats the controller.

A

a. Its movement corresponds to the direction of deviation of the controlled device.

73
Q

(426) What does a microprocessor do after it accepts inputs and stores them?
a. Creates its own creative output.
b. Creates a pre-programmed output.
c. Holds on to them for up to 45 years.
d. Creates an output for the sensor.

A

b. Creates a pre-programmed output.

74
Q

(427) What causes the temperature changes sensed by an averaging bulb?
a. Stratification.
b. Motor efficiency.
c. External static pressure.
d. Pre-programmed output.

A

a. Stratification.

75
Q

(428) What does a minimum position selector use to select its output?
a. Motor amperage.
b. Compressor amperage.
c. System control points.
d. The minimum output selected for that controller.

A

d. The minimum output selected for that controller.

76
Q

(428) Where does an electronic actuator receive its direct current (DC) voltage?
a. From the sensor.
b. From a controller.
c. From the controlled device.
d. From the motor controller.

A

b. From a controller.

77
Q

(429) What gives the engineers flexibility when creating customer comfort?
a. Air handling equipment or pumps.
b. Minimum output controllers.
c. Variable frequency drives (VFD).
d. Dampers.

A

c. Variable frequency drives (VFD).

78
Q

(429) Where does the variable frequency drive (VFD) receive its feedback control?
a. From the refrigerant gauges.
b. From the controlled device.
c. Internally or externally.
d. Internally only.

A

c. Internally or externally.

79
Q

(430) What is required for the energy monitoring control systems (EMCS) and direct digital control (DDC) components to communicate?
a. A modem from your shop.
b. A modem at the DDC.
c. A modem at EMCS.
d. A modem at both locations.

A

d. A modem at both locations.

80
Q

(430) Where can a technician make changes to a direct digital control (DDC) system?
a. From a computer in the shop or laptop in mechanical rooms.
b. From a government computer at your house.
c. Only in mechanical rooms.
d. By setting linkages.

A

a. From a computer in the shop or laptop in mechanical rooms.

81
Q

(430) What should be the state of outdoor air dampers during preoccupancy warm-up periods for optimum start?
a. Inactive.
b. Active.
c. 100 percent open.
d. 75 percent open.

A

a. Inactive.

82
Q

(430) What air source does early morning purge use to precool a building?
a. Mixed air.
b. Return air.
c. Outdoor air.
d. Supply air.

A

c. Outdoor air.

83
Q

(431) What will a direct digital control (DDC) processor probably do after it receives its input and processes the information?
a. Produce its own input.
b. Produce an output.
c. Control the sensor output.
d. Control the sensor input.

A

b. Produce an output.

84
Q

(431) What proportional plus integral plus derivative (PID) action acts as a brake to stop the controller at set point and prevent overshoot?
a. Derivative action.
b. Floating control.
c. On-off control.
d. Integral control.

A

a. Derivative action.

85
Q

(432) What is a modulating signal from a direct digital control (DDC) to a particular device?
a. Digital output.
b. Analog output.
c. Digital input.
d. Analog input.

A

b. Analog output.

86
Q

(432) When the direct digital control (DDC) sends a small amount of current through the thermistor circuit, what does it then do to the input current coming back from the thermistor?
a. Performs a derivative action.
b. Translates it into a temperature.
c. Discards it to the floating control.
d. Translates it to a signal back to the sensor.

A

b. Translates it into a temperature.

87
Q

(432) Why would you choose to install electric reheat over reheat water coils?
a. Electric reheat is more expensive to install but more efficient to operate.
b. Reheat coils are less expensive to install but more costly to operate.
c. Electric reheat is the industry standard.
d. Electric reheat is cheaper to install.

A

d. Electric reheat is cheaper to install.

88
Q

(433) On a central air-handling unit, which components turns on with the fan and also provides an emergency shutdown feature?
a. Firestats and freezestats.
b. Closed oil pressure switches.
c. Freezestats and closed oil pressure switches.
d. Firestats, smoke detectors, and airflow switches.

A

a. Firestats and freezestats.

89
Q

(433) How many degrees Fahrenheit (F) above the normally expected temperature are supply duct firestats set?
a. 10.
b. 30.
c. 50.
d. 150.

A

c. 50.

90
Q

(433) Roll-feed media filters may be automatically controlled by
a. the variable air volume (VAV) temperature.
b. pressure-activated timer circuit.
c. temperature-activated timer circuit.
d. the technician removing the filter.

A

b. pressure-activated timer circuit.

91
Q

(434) In a mixed-air system, if outdoor air temperature is higher than the conditions where free cooling can be obtained, what will the outdoor air controller do?
a. Shut the damper.
b. Open the damper 50 percent.
c. Open the damper 25 percent.
d. Shut the damper 60 percent.

A

a. Shut the damper.

92
Q

(434) For space and zone control, where can the control of a coil come from?
a. Dampers.
b. Valve actuators.
c. The controlled device.
d. The controlled space.

A

d. The controlled space.

93
Q

(434) What type of relationship occurs if the reset variable increases and the primary set point goes down?
a. Observed.
b. Reverse.
c. Offset.
d. Inverted.

A

b. Reverse.

94
Q

(435) What two things does a reheat subsystem control depend on?
a. Wet bulb temperature.
b. Specific and relative humidity.
c. Temperature and relative humidity.
d. Temperature and specific humidity.

A

c. Temperature and relative humidity.

95
Q

(435) Besides cooling the air, what other function does the chilled-water coil do?
a. Heat.
b. Humidify.
c. Dehumidify.
d. Increase grains of moisture.

A

c. Dehumidify.

96
Q

(435) What must be used as the result of low relative humidity in the conditioned space?
a. Chilled water cooling and dehumidifying.
b. Steam coils to reheat air.
c. Dehumidifier.
d. Humidifier.

A

d. Humidifier.

97
Q

(435) What can be used to prevent relative humidity in the duct from rising too high?
a. Actuators.
b. Dampers.
c. Sensor/controller.
d. Controlled device.

A

c. Sensor/controller.

98
Q

(435) In a multiple-zone system, how can each zone draw as much hot or cold air as it requires?
a. By using a dependently controlled set of mixing dampers provided for each zone.
b. By using an independently controlled set of mixing dampers provided for each zone.
c. By using the set of mixing dampers provided for all zones.
d. By using bypass zoning.

A

b. By using an independently controlled set of mixing dampers provided for each zone.

99
Q

(435) In a multiple-zone system, the coil discharge temperatures are based on the
a. return air temperature of one zone.
b. average building temperature.
c. worst case zones (the largest heating and cooling loads).
d. best case zones (the smallest heating and cooling loads).

A

c. worst case zones (the largest heating and cooling loads).

100
Q

(435) By what percent can a hot deck increase operating cost if it was 10 degrees Fahrenheit warmer than needed?
a. 30.
b. 40.
c. 50.
d. 60.

A

a. 30.

HVAC CDC's (5 decks)

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