NATE Final Exam #2

Created by dddpope Plus

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A condensing unit should be mounted on a slab that is level to:

A: Allow any accumulated water to evenly run out of the cabinet

B: Increase airflow through the fin area

C: Prevent the unit from tipping over

D: Make certain any top discharge air blows straight up

A: Allow any accumulated water to evenly run out of the cabinet

A simple time-activated switch is an example of a control that does not use:

A: Feedback

B: Electronics

C: Calibration

D: Manual adjustment

A: Feedback

Which of the following systems would typically require a blower with a 2000 cfm output?

A: 2-ton ac system

B: 3-ton ac system

C: 5-ton ac system

D: 7.5-ton ac system

C: 5-ton ac system

400 cfm/ton X 5 ton = 2000 cfm

A typical induced-draft furnace uses a blower-off delay in the cooling mode to:

Increase the efficiency of the system

Which of the following would a technician use to check the operating sequence of an air conditioning system?

A: Schematic

B: Warranty Information

C: Furnace manual

D: All of the above

A: Schematic

Wood studs in typical residential construction are how far apart?

16 inches

Which of the following components is energized first after an intermittent ignition gas furnace calls for heat?

A: Induced draft motor

B: Pilot valve

C: Blower motor

D: Gas valve

A: Induced draft motor

To have a system automatically switch to heating or cooling as the load changes, the thermostat:

A: System switch should be in auto

B: System switch should be in off

C: System switch should be on

D: Fan switch should be in auto

A: System switch should be in auto

A typical heat pump uses a high-pressure control to shut off the compressor if the condensing pressure becomes excessive. The control uses a switch that makes the compressor contact on a pressure:

A: Rise at the compressor discharge

B: Fall at the compressor discharge

C: Difference between the high and low side

D: Combination of the high and low side

B: Fall at the compressor discharge

The number 3,412 btu is equal to:

A: 1 watt

B: 3.4 watts

C: 1 kilowatt

D: 3.4 kilowatts

C: 1 kilowatt

Gas heating systems on roofs or other elevated locations shall be accessible by way of the building if the building is taller than:

A: 10 feet

B: 15 feet

C: 20 feet

D: 25 feet

B: 15 feet

Which of the following is typically covered by local codes?

A: Minimum cfm per outlet

B: Maximum length of a trunk

C: Termination of condensate line

D: Refrigerant charge

C: Termination of condensate line

What is the difference between the wiring of an electromechanical thermostat and an electronic thermostat?

A: Both the hot leg and the common of a 120-volt supply must be run to the electronic thermostat.

B: Typically there is no difference, they are designed to be interchangeable.

C: Wire size used on the electronic thermostat must be larger.

D: Both the low voltage hot and common must be run to the electronic thermostat.

B: Typically there is no difference, they are designed to be interchangeable.

A secondary drain pan is used when an air conditioning system is located:

A: Above a ceiling

B: In a closet

C: Below grade

D: More than 30 feet from a useable drain

A: Above a ceiling

A person is sitting near a cold window on a winter day. They are losing heat to the cold window by:

A: Conduction

B: Convection

C: Radiation

D: Evaporation

C: Radiation

In electrical wiring, the black conductor usually indicates:

A: The hot conductor

B: The neutral conductor

C: The ground wire

D: The safety wire

A: The hot conductor

Which of the following is the correct equation for determining wattage in an electrical circuit?

A: W = P x I

B: W = E x I

C: W = I x R

D: W = E x R

B: W = E x I

The rpm of a motor is determined by:

A: The motor's voltage

B: The motor's amperage

C: The number of poles

D: The size of the motor windings

C: The number of poles

An ohmmeter reading of infinity across a switch means:

A: The switch is open

B: The switch is closed

C: The switch is good

D: The switch is bad

A: The switch is open

The synchronous speed of a four-pole 60 Hz single-phase motor is:

A: 3600 rpm

B: 1500 rpm

C: 3450 rpm

D: 1800 rpm

D: 1800 rpm

RPM = 120 X (Freq/#poles)
RPM = 120 X (60/4) = 1800

Contactors are rated according to the maximum amperage through the:

A: Coil

B: Contacts

C: Thermostat

D: Fuse

B: Contacts

Lowering the airflow over an evaporator will:

A: Increase the temperature drop of the air and increase the amount of moisture removed from the air

B: Decrease the temperature drop of the air and increase the amount of moisture removed from the air

C: Increase the temperature drop of the air and decrease the amount of moisture removed from the air

D: Decrease the temperature drop of the air and decrease the amount of moisture removed from the air

A: Increase the temperature drop of the air and increase the amount of moisture removed from the air

What is the temperature rise of 250 cfm of air if an electric heater adds 8,500 btuh to the air?

A: 18 degrees F

B: >27 degrees F

C: 31.5 degrees F

D: 40 degrees F

C: 31.5 degrees F

Temp. rise X 1.08 X CFM = BTUS
Temp. rise = (BTUS/1.08)/CFM
Temp. rise = (8500/1.08)/250
Temp. rise = 31.48

When a compressor service valve is located on the compressor discharge and is back-seated, _______.

A: the compressor is connected to the discharge piping

B: the back-seat port is closed to the compressor

C: the front-seat port is open to the compressor

D: All of the above are true

D: All of the above are true

The maximum secondary amperage of a 40VA, 240 by 24 volt control transformer would be:

A: 1.6 amps

B: 6.0 amps

C: 10.5 amps

D: 0.16 amps

A: 1.6 amps

P = E X I
I = P/E
I = 40/24 = 1.6666666 amps

A combination electrode/nozzle gauge can be used to perform which of the following tasks?

A: Remove the spark electrode

B: Remove the burner nozzle head

C: Measure the nozzle pressure

D: Position the nozzle to the burner head

D: Position the nozzle to the burner head

A single-trunk duct system that extends in one or two directions from the unit and has multiple branches is a (an):

A: Perimeter duct system

B: Extended plenum duct system

C: Radial duct system

D: Reducing trunk system

B: Extended plenum duct system

After cutting copper tubing, the tube edge should be cleaned with a:

A: Wire brush

B: Hacksaw blade

C: Round file

D: Reamer

D: Reamer

Which of the following is covered by the National Fire Protection Code?

A: Wire sizing

B: Use of return air sensors

C: Locations of service platforms

D: Clearances around condensing units

A: Wire sizing

Maintaining manufacturer-specified clearances on all sides of a condensing unit is:

A: Necessary in residential applications only

B: Necessary in commercial applications only

C: Only necessary if required by local codes

D: Necessary whenever locating the equipment

D: Necessary whenever locating the equipment

Of the following, which is most likely powered by a supply voltage of 240V single-phase?

A: Natural gas furnace

B: Residential condensing unit

C: Commercial packaged unit

D: Residential humidifier

B: Residential condensing unit

Which of the following would be considered a good location to mount a wall thermostat?

A: In a kitchen

B: In a bathroom

C: On an exterior wall

D: Near a return grille

D: Near a return grille

To have a system automatically switch to heating or cooling as the load changes, the thermostat must have:

A: System switch set in the cooling position

B: System switch set in the heating position

C: Fan switch set in the auto position

D: System switch set in the auto position

D: System switch set in the auto position

A heat pump operating in the heating mode with inadequate airflow across the indoor coil will typically have which of the following symptoms?

A: A higher than normal temperature rise across the outdoor coil

B: A lower than normal temperature rise across the outdoor coil

C: A higher than normal temperature rise across the indoor coil

D: A lower than normal temperature rise across the indoor coil

C: A higher than normal temperature rise across the indoor coil

Condensate piping must be properly trapped to prevent:

A: Ice formation in colder temperatures

B: Condensate running off the evaporator coil

C: Condensate overflowing the drain pan

D: Excessive air noise in the piping

C: Condensate overflowing the drain pan

A BTU is defined as the amount of heat that must be added to one ________ of water to raise its temperature one degree Fahrenheit.

A: pound

B: ounce

C: quart

D: gallon

A: pound

In a simple resistive circuit, the voltage is 24 volts and the current is 8 amps. According to Ohm's law the resistance is:

A: 16 ohms

B: 3 ohms

C: 192 ohms

D: 0.5 ohms

B: 3 ohms

E = I x R
R = E/I
R = 24/8 = 3 ohms

A traverse joint is used to connect:

A: Electrical wiring

B: Ductwork

C: Refrigerant piping

D: Condensate pipe

B: Ductwork

To determine the amount of sensible heat added to the refrigerant above the saturation point in an evaporator, the installer would:

A: Perform a subcooling check on the liquid line

B: Perform a superheat check on the evaporator line

C: Perform a cfm check across the evaporator coil

D: Perform a delta T check across the evaporator coil

B: Perform a superheat check on the evaporator line

To check a de-energized, normally-open relay for fused contacts, a VOM would be set to check:

A: Amps

B: Voltage

C: Current

D: Ohms

D: Ohms

Which of the following oil furnace components should be replaced annually?

A: Burner head

B: Fuel filter

C: Flame prover

D: Combustion chamber

B: Fuel filter

Pigtail 120 volt wires should be connected to the supply wiring by twisting the appropriate wires together, insulating and securing each connection with:

A: Duct tape

B: Plastic tape

C: Wire nuts

D: Rubber electrical tape

C: Wire nuts

Which of the following components is typically used only on induced draft condensing gas furnaces?

A: Electronic fan control

B: Hot surface ignition

C: Induced draft blower motor

D: Secondary heat exchanger

D: Secondary heat exchanger

Proper control of temperature, humidity, air movement, air cleanliness and fresh air ventilation is:

A: To achieve a total comfort level in residential HVAC applications only

B: To achieve a total comfort level in commercial HVAC applications only

C: To achieve a total comfort level in any structure

D: To achieve a total comfort level in Southern states onl

C: To achieve a total comfort level in any structure

7,000 BTU is approximately equal to _______ KW.

A: one

B: two

C: three

D: four

B: two

There are 3.41 btus per watt or 3410 btus per KW. 7000/3410 = 2.053 KW

Which precaution should an installer perform to keep copper from oxidizing internally while brazing a connector to the tube?

A: Hold the torch flame centered over the connector

B: Purge the tube with an inert gas such as nitrogen

C: Increase torch flame to its maximum setting

D: Hold the torch flame on the tubing only

B: Purge the tube with an inert gas such as nitrogen

After connecting two sections of metal ductwork using drive cleats, you should:

A: Bend the ends of the drives over the duct

B: Bend the ends of the drives away from the duct

C: Cut the ends of the drives off

D: Crimp the ends of the drives and cut off

A: Bend the ends of the drives over the duct

The term sheathing in the building trade refers to:

A: Lumber used between roof beams or rafters as a base for roofing material

B: Lumber used to brace interior and exterior walls

C: Interior sheet rock

D: Plywood decking in an attic

A: Lumber used between roof beams or rafters as a base for roofing materia

Which of the following areas of metal air duct design is often governed by municipal codes?

A: The size of air ducts

B: The number of duct fittings

C: Thickness of duct insulation

D: Type of connections made at duct joints

C: Thickness of duct insulation

A customer needs the outdoor condensing unit replaced. Which of the following should the size of the outdoor unit be based upon?

A: The cooling load of the space

B: The capacity of the evaporator

C: The size of the slab

D: The available clearances around the unit

B: The capacity of the evaporator

Customer complaints of "cold air blowing" from the registers of a properly charged heat pump system may be rectified by:

A: All supply registers are slightly undersized to increase air velocity

B: Any sidewall mounted supply registers are slightly over-sized to increase air velocity

C: Only ceiling supply registers are slightly undersized to increase air velocity

D: All supply registers are sized correctly for both throw and velocity

D: All supply registers are sized correctly for both throw and velocity

Don't understand this answer, unless it is referring to the fact that the temperature rise of a heat pump, by nature, is low then a gas furnace.

Fresh air intake ducts, used to route outdoor air to interior spaces, connect to the:

A: Vent piping

B: Combustion air duct

C: Supply side of the duct system

D: Return side of the duct system

D: Return side of the duct system

According to the Uniform Mechanical Code, an attic-mounted furnace must have a permanently mounted light fixture. Where must the switch which controls this light be located?

A: At the main circuit panel

B: Within reach of the furnace

C: Within sight of the furnace

D: At the required passageway opening

D: At the required passageway opening

In the following sentence, which of the choices below would best simplify and still express the nearest meaning of the statement: "In my opinion, the new thermostat design is a change for the better."

A: An improvement

B: A step in the right direction

C: A help

D: A badly needed modification

A: An improvement

Metal duct that has hung for several years must be checked for sags and misalignment's because:

A: They can place excessive stress on joints and seals

B: They increase static pressure in the duct

C: They decrease static pressure in the duct

D: They increase CFM at the diffusers

A: They can place excessive stress on joints and seals

The typical procedure for repairing a small tear in the outer foil covering of a duct-board plenum is to:

A: Cover the tear with a vapor barrier such as a piece of plastic

B: Cover the tear with an approved foil tape

C: Wrap the section of duct-board with insulation

D: Cut out an area 2 inches larger than the cut and insert a replacement plug

B: Cover the tear with an approved foil tape

A thermistor is a component used in an electronic wall thermostat to measure:

Temperature

Two-stage heat, single-stage cool thermostats are typically used on dual fuel heat pump systems that use oil heat for second stage heating. How would the heat pump operate if the second stage of the thermostat had an open circuit on an extremely cold day? Assume the emergency heat switch is not turned on.

A: The heat pump will operate on calls for heat without energizing the oil furnace

B: The oil furnace will operate on calls for heat without energizing the heat pump.

C: Neither the heat pump nor the oil furnace will operate in heating modes.

D: The oil furnace will operate in emergency heat mode only.

A: The heat pump will operate on calls for heat without energizing the oil furnace.

Note: If the system is equipped with an outside thermostat that shuts down the heat pump, Aux heat would come on in that event.

The slope of the condensate lines in an attic are often set by:

A: Uniform Mechanical Code

B: Underwriter

C: AGA

D: ARI

A: Uniform Mechanical Code

Which of the following joints, when properly done, will best join a copper tube to a copper fitting?

A: Compression

B: Flare

C: Sweat

D: Interference

C: Sweat

Suction line refrigerant pressure and temperature are measurements needed to determine the:

A: Air temperatures entering and leaving the evaporator coil

B: Amount of refrigerant in a system

C: Sub-cooling of refrigerant leaving a condensing coil

D: Superheat in the refrigerant leaving an evaporator

D: Superheat in the refrigerant leaving an evaporator.

On start-up, a natural gas heating system has "cold air" blowing from the registers. What could be the problem?

A: Burner manifold pressure is too high

B: Supply duct runs are too short

C: Blower "ON" delay is set too short

D: Blower "ON" delay is set too long

C: Blower "ON" delay is set too short

A PSC condenser fan motor is not operating but the compressor runs. A voltage check of the condenser fan motor shows no voltage at the motor. Which of the following may be the cause?

A: Open run capacitor

B: Shorted run capacitor

C: Open motor windings

D: Poor or open wiring connection

D: Poor or open wiring connection

Which of the following statements is true concerning state and local codes and regulations?

A: Local codes never override state codes

B: Local codes always override state codes

C: State codes always contain regulations that are more strict than local codes

D: Local codes must be followed if they are more strict than state codes

D: Local codes must be followed if they are more strict than state codes

Which of the following instruments would typically be used to measure static and total pressure in a duct system?

A: Psychrometer

B: Pitot-tube

C: Portable air hood

D: Anemometer

B: Pitot-tube

Which of the following instruments must be used with the power de-energized?

A: Voltmeter

B: Ohmmeter

C: Ammeter

D: Watt-meter

B: Ohmmeter

A customer asks you to do something that your company rules specifically prohibit. When responding to their request you should:

A: Tell the customer you cannot comply with his request and leave it at that

B: Explore with the customer the circumstances under which you might do it

C: Tell the customer you cannot comply with his request and offer a brief explanation why you can't

D: Whenever possible prevent a conflict and go ahead and do it

C: Tell the customer you cannot comply with his request and offer a brief explanation why you can't

Blower belt noise is caused by which of the following?

A: Over voltage to the motor

B: Worn pulley

C: Under voltage to the motor

D: Wrong blower wheel

B: Worn pulley

While checking the installation of attic-mounted flexible duct, you find 7 to 9 foot spacing between duct supports. What steps if any, should be taken?

A: No steps are necessary unless the spacing is greater than 10 feet

B: No steps are necessary since the spacings are greater than 5 fee

C: All supports must be relocated to maintain a maximum spacing of 5 feet

D: All supports must be relocated to maintain a minimum spacing of 7 feet

A: No steps are necessary unless the spacing is greater than 10 feet

A vapor-charged temperature control uses what in its power element?

A: Oil

B: Water

C: Antifreeze

D: Refrigerant

D: Refrigerant

Isolation collars are typically added to duct-work to:

A: Reduce vibration noise

B: Reduce static pressure

C: Reduce heat gain

D: Increase air velocity

A: Reduce vibration noise

On a typical 120 volt three-prong electrical receptacle, the hot wire should be:

A: The narrow slot

B: The wide slot

C: Both the narrow and wide slots

D:The round slot

A: The narrow slot

Each phase of three-phase power is ______ degrees out of phase from each other.

120 degrees

Two 5mfd capacitors are in series with one another. The total capacitance of the two is:

2.5mfd

Three 10mfd capacitors are connected in parallel with each other. The total capacitance of the three is:

30mfd

The air temperature drop across an evaporator is measured and determined to be 30 degrees Fahrenheit. Which of the following is most likely true?

A: There is too much evaporator airflow

B: There is too little evaporator airflow

C: The system is overcharged

D: The system is undercharged

B: There is too little evaporator airflow

The square root of the number 9 is:

3

Air flows from an 8-inch duct where the duct is reduced to 6 inches. Which of the following is true?

A: The air velocity increases

B: The air velocity decreases

C: The CFM increases

D: The CFM stays the same

A: The air velocity increases

Which of the following is true about compression ratio?

A: It is the absolute high side pressure divided into the absolute suction pressure.

B: It is the absolute suction pressure divided into the absolute high side pressure.

C: It is the high side pressure in psig divided into the suction pressure in psig.

D: It is the suction pressure in psig divided into the high side pressure in psig.

B: It is the absolute suction pressure divided into the absolute high side pressure.

The speed of a three-phase motor is determined by:

The frequency of the power supplied to the motor

Which one of the following fuse types should be used to protect the condensing unit on a residential split system air conditioning system?

A: Time-delay

B: Instant-blow

C: Fast-reacting

D: Series-rated ground-faul

A: Time-delay

Which of the following organizations rates electrical components and equipment for electrical safety?

A: ARI

B: UL

C: RSES

D: ASHRAE

B: UL

On a heat pump the "balance point" is:

A: The point at which the heat loss of a structure matches the heat pump capacity

B: The point at which the heating load calculation matches the cooling load calculation

C: The lowest effective outside temperature at which the heat pump can operate

D: The most effective temperature where the heat pump's electric auxiliary heat should be energized

A: The point at which the heat loss of a structure matches the heat pump capacity

On a system using a reciprocating compressor, raising the evaporator pressure and/or lowering the condensing pressure will:

A: Decrease the compressor's volumetric efficiency

B: ncrease the compressor's volumetric efficiency

C: Have no effect of volumetric efficiency

D: Increase the compressor's power consumption

B: Increase the compressor's volumetric efficiency

A heat anticipator in a typical thermostat is wired:

A: In series with the "R" terminal

B: In parallel with the "R" terminal

C: In series with the "W" terminal

D: In parallel with the "W" terminal

C: In series with the "W" terminal

To test a capacitor with an ohmmeter, the ohmmeter should be set at:

A: The R times 1 scale

B: The R times 10 scale

C: The R times 100 scale

D: The highest ohms scale available

D: The highest ohms scale available

Which of the following is considered a good evacuation?

A: 2000 microns

B: 1500 microns

C: 1000 microns

D: 500 microns or less

D: 500 microns or less

A filter-drier has a temperature drop across it. Which of the following is true about the filter-drier?

A: It is partially plugged

B: It is totally plugged

C: A temperature drop across it is normal

D: The filter-drier has not yet broken in

A: It is partially plugged

An FRN-R fuse is:

A: A time-delay fuse

B: An instant-blow fuse

C: Neither A nor B is true

D: Only used on non-inductive circuits

A: A time-delay fuse

A fuse must be selected according to:

A: Type, amperage and voltage

B: Type and amperage

C: Type and voltage

D: Type, amperage, voltage and wattage

A: Type, amperage and voltage

On a typical three-terminal single-phase fully hermetic compressor, between which two terminals is the start winding located?

A: The two with the highest resistance

B: The two with the least resistance

C: The two with the middle resistance

D: The two with continuity to ground

C: The two with the middle resistance

A Ground Fault Circuit Interrupter monitors:

A: The current between the hot wire and ground

B: The current between the hot wire and the neutral wire

C: The current between the neutral wire and ground

D: The voltage across the line

B: The current between the hot wire and the neutral wire

Typical bypass humidifiers are connected:

A: Between the supply and the return ducts

B: Between the supply and outside air intake

C: Between the outside air intake and return air duct

D: Between the exhaust air and return air duct

A: Between the supply and the return ducts

The typical bypass humidifier does not work well with which of the following heating system types?

A: Natural gas

B: Propane gas

C: Heat pumps and electric heat

D: Oil-fired furnaces

C: Heat pumps and electric heat

During the heating season a damper located in the bypass duct of a bypass humidifier must be:

A: Closed

B: Open

C: Adjusted according to the temperature rise of the furnace

D: Adjusted according to the total cfm of the duct system.

B: Open

As air is heated, its relative humidity:

Decreases

A sling Psychrometer measures:

Dry and wet bulb temperatures, which can be used to determine relative humidity.

A protractor is best used to:

Lay out angles

Which of the following is the most accurate method of balancing a duct system?

A: Proportional balancing

B: Sequential balancing

C: Temperature balancing

D: Total pressure balancing

A: Proportional balancing

Which of the following statements most correctly defines the difference between "accuracy" and "precision" in instruments?

A: There is no difference between the two terms.

B: "Accuracy" - how close the measurement is to the actual value. "Precision" - how small a value can be measured.

C: "Accuracy" - how small a value can be measured. "Precision" - how close the reading is to the actual value.

D: "Accuracy" - repeatability of the measurement. "Precision" - percentage of error in the reading.

B: "Accuracy" - how close the measurement is to the actual value. "Precision" - how small a value can be measured.

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