Mechanical Engineering Unit 41 To 50 Which Type Duct Undergoes More Rigorous Testing Before Labeled Galvanized Sheet Metal

154)

Which type of duct undergoes more rigorous testing before it is labeled?

A)

Galvanized sheet metal duct

B)

Flexible duct

C)

Polycarbonate molded duct

D)

Flexible duct connector

Answer:

B

Explanation:

A)

B)

C)

D)

155)

A ________ duct system uses several large ducts leaving the main plenum that branch off into

smaller ducts as they get closer to their destination.

A)

closed loop system

B)

reducing radial duct system

C)

central plenum system

D)

perimeter loop system

Answer:

B

Explanation:

A)

B)

C)

D)

156)

Which class of manufactured duct has the lowest flame spread and smoke developed ratings?

A)

Ductwork does not burn.

B)

Class 0

C)

Class 1

D)

Class 2

Answer:

B

Explanation:

A)

B)

C)

D)

157)

How does a duct blaster measure air leakage in duct systems?

A)

It measures the actual leakage area through reflected pressure waves.

B)

It uses a velocimeter to calculate the speed of the sonically diffused airstream.

C)

It measures the time it takes the duct system to depressurize.

D)

It measures the airflow required to maintain a specified pressure.

Answer:

D

Explanation:

A)

B)

C)

D)

41

158)

Using the percentage of design flow method, a system that leaks 100 CFM in a system with a

design flow of 1,200 CFM has a leakage rate of:

A)

1,200 CFM – 100 CFM = 11% leakage rate.

B)

1,200 CFM/100 CFM = 12% leakage rate.

C)

100 CFM/1,200 CFM = 8% leakage rate.

D)

100 CFM/(1,200 CFM – 100 CFM) = 9% leakage rate.

Answer:

C

Explanation:

A)

B)

C)

D)

159)

Rectangular sheet metal ducts are joined together using:

A)

Mastic.

B)

Duct tape.

C)

S–locks and drives cleats.

D)

Flanges and bolts.

Answer:

C

Explanation:

A)

B)

C)

D)

160)

The maximum installed length of a flexible air connector is:

A)

25 ft.

B)

14 ft.

C)

10 ft.

D)

Unlimited.

Answer:

B

Explanation:

A)

B)

C)

D)

161)

There are many methods of insulating metal ductwork. Which of the following methods is NOT

used to insulate ducts?

A)

Fiberglass outerwrap with vapor barrier

B)

Spray–on urethane foam

C)

Fiberglass liner

D)

Bubble outer wrap or liner

Answer:

B

Explanation:

A)

B)

C)

D)

42

162)

A common cause of poor airflow is:

A)

Unusual airflow restrictions in the duct.

B)

A duct system that has been sealed too tight and cannot breathe.

C)

Unusually large ductwork.

D)

Improper installation of the thermostatic expansion valve.

Answer:

A

Explanation:

A)

B)

C)

D)

163)

Fault isolation diagrams and troubleshooting tables help the technician locate problems through

the process of:

A)

Elimination.

B)

Extrapolation.

C)

Sublimation.

D)

Interpolation.

Answer:

A

Explanation:

A)

B)

C)

D)

164)

Symptoms of an inefficient compressor include:

A)

Low suction pressure, low discharge pressure, and high amp draw.

B)

High suction pressure, low discharge pressure, and low amp draw.

C)

Low suction pressure, high discharge pressure, and high amp draw.

D)

High suction pressure, high discharge pressure, and low amp draw.

Answer:

B

Explanation:

A)

B)

C)

D)

165)

When charging a capillary tube system that holds 100 oz., the charge must be:

A)

Within 1 percent, between 99 and 101 oz.

B)

Within 10 percent, between 90 and 110 oz.

C)

Within 5 percent, between 95 and 105 oz.

D)

Equal to or greater than 100 oz.

Answer:

C

Explanation:

A)

B)

C)

D)

43

166)

A high temperature differential (more than 2 degrees) between return air temperature at the grille

and the return air temperature at the unit indicates:

A)

Low refrigerant charge.

B)

Clogged liquid line.

C)

Return air leakage.

D)

Dirty evaporator coil.

Answer:

C

Explanation:

A)

B)

C)

D)

167)

How can a technician check to see if the coil and condensing unit on an AC split system are

matched?

A)

Check to see that both pieces are manufactured by the same company.

B)

The refrigerant line stub out sizes should be the same.

C)

The first two digits of the equipment model number should be the same.

D)

Call the equipment supplier and provide the system model numbers.

Answer:

D

Explanation:

A)

B)

C)

D)

168)

A split–system air conditioner that does not operate at all most likely has:

A)

An airflow problem.

B)

An inefficient compressor.

C)

A refrigeration problem.

D)

An electrical problem.

Answer:

D

Explanation:

A)

B)

C)

D)

169)

The evaporator coil operating temperature for a system with a 20°F split, 85°F return air, and 71°F

supply air is:

A)

COT = ((85°F – 71°F)/2) + 20 = 98°F.

B)

COT = 71°F – 20 = 51°F.

C)

COT = 85°F – 20 = 75°F.

D)

COT = ((85°F – 71°F)/2) – 20 = 58°F.

Answer:

D

Explanation:

A)

B)

C)

D)

44

170)

Normally, a split AC system that uses a fixed metering device can safely operate at temperatures:

A)

Above 65°F.

B)

Above 50°F.

C)

Above 70°F.

D)

Above 90°F.

Answer:

A

Explanation:

A)

B)

C)

D)

171)

The most common cause of airflow–related problems in air–conditioning units is:

A)

Dirty condenser coils.

B)

Electrical issues.

C)

Low refrigerant charge.

D)

Dirty air filters.

Answer:

D

Explanation:

A)

B)

C)

D)

172)

The refrigerant condensing temperature for an air–cooled system having a 20°F split is:

A)

RCT = 95°F + (20°F/2) = 105°F.

B)

RCT = 95°F – 20°F = 75°F.

C)

RCT = 95°F – (20°F/2) = 85°F.

D)

RCT = 95°F + 20°F = 115°F.

Answer:

D

Explanation:

A)

B)

C)

D)

173)

When the liquid line is restricted, the supply of refrigerant to the metering device is reduced.

What is the effect on suction pressure and superheat?

A)

Suction pressure goes down and superheat increases.

B)

No change in the suction pressure

C)

Suction is increased and superheat increased.

D)

Suction is decreased and superheat decreased.

Answer:

A

Explanation:

A)

B)

C)

D)

45

174)

The expected temperature drop through a direct expansion evaporator coil:

A)

Should be 10°F.

B)

Should be 20°F.

C)

Should be 15°F.

D)

Can be determined with a chart supplied by the coil manufacturer.

Answer:

D

Explanation:

A)

B)

C)

D)

175)

Electronic controls on air–conditioning systems typically report faults by:

A)

Texting the technician’s cell phone.

B)

Indicating a fault code.

C)

Not working.

D)

E–mailing the company.

Answer:

B

Explanation:

A)

B)

C)

D)

176)

How do water and carbon dioxide relate to combustion?

A)

Water, not carbon dioxide, is a product of combustion.

B)

Both are unstable, dangerous products of combustion.

C)

Both are stable and safe products of combustion.

D)

Carbon dioxide, not water, is a product of combustion.

Answer:

C

Explanation:

A)

B)

C)

D)

177)

A combination of two elements makes up common fuel gases. Which of the following elements

make up these fuel gases?

A)

Carbon and fluoride

B)

Hydrogen and carbon

C)

Hydrogen and oxygen

D)

Carbon and oxygen

Answer:

B

Explanation:

A)

B)

C)

D)

46

178)

The approximate heating value of methane is:

A)

1,780 BTU per cubic foot.

B)

1,000 BTU per cubic foot.

C)

3,200 BTU per cubic foot.

D)

2,500 BTU per cubic foot.

Answer:

B

Explanation:

A)

B)

C)

D)

179)

What causes flue gas condensation?

A)

The flue gas is cooled below the dewpoint of the combustion gas.

B)

Operating the furnace during times of high relative humidity

C)

Cold air being pulled through the vent on the off cycle drops the vent temperature below

the dewpoint of the surrounding air.

D)

Water naturally condenses on metal surfaces.

Answer:

A

Explanation:

A)

B)

C)

D)

180)

What is the type of gas that is created as a byproduct of other manufacturing processes?

A)

Manufactured gas

B)

Natural gas

C)

Liquid petroleum

D)

Propane

Answer:

A

Explanation:

A)

B)

C)

D)

181)

How does negative pressure affect the air supply of a furnace?

A)

It causes a need for less outside air.

B)

It causes little noticeable change to a furnace.

C)

It increases the need for outside air.

D)

It increases the furnace’s need for gas.

Answer:

C

Explanation:

A)

B)

C)

D)

47

182)

Once a technician works on a system, what else should he or she do?

A)

Check for gas leaks.

B)

Increase household ventilation.

C)

Open the gas flow valve.

D)

Do nothing else.

Answer:

A

Explanation:

A)

B)

C)

D)

183)

Air that is mixed with the fuel before it is ignited is referred to as:

A)

Ignition air.

B)

Combustion air.

C)

Primary air.

D)

Secondary air.

Answer:

C

Explanation:

A)

B)

C)

D)

184)

What part does heat play in combustion?

A)

Heat causes combustion to end.

B)

Heat plays no role in combustion.

C)

Heat is a byproduct of combustion.

D)

Heat is the catalyst of combustion.

Answer:

D

Explanation:

A)

B)

C)

D)

185)

What is the purpose of excess air in furnace combustion?

A)

Excess air is used for creating a high–fire second stage of combustion.

B)

Excess air ensures that all the gas is burned by making sure there is plenty of oxygen

available.

C)

Excess air improves the draft efficiency by raising the combustion gas temperature.

D)

Excess air ensures that the heat exchanger does not overheat.

Answer:

B

Explanation:

A)

B)

C)

D)

48

186)

Which of the following is a product of complete combustion?

A)

Oxygen

B)

Methane

C)

Carbon monoxide

D)

Water vapor

Answer:

D

Explanation:

A)

B)

C)

D)

187)

How was natural gas created?

A)

Chemicals are mixed in large gas generating plants that react to form natural gas.

B)

Natural gas was created when the earth was formed.

C)

Natural gas is a byproduct of refining oil.

D)

Conversion of organisms into gas through pressure and heat

Answer:

D

Explanation:

A)

B)

C)

D)

188)

Compared to blue flames, yellow flames:

A)

Produce about the same amount of heat.

B)

Burn more cleanly.

C)

Burn at a lower temperature.

D)

Burn at a higher temperature.

Answer:

C

Explanation:

A)

B)

C)

D)

189)

What type of measurement is a grain?

A)

A grain is a small measurement of weight.

B)

A grain is a small measurement of volume.

C)

A grain is equal to one drop of water.

D)

A grain is theoretically extrapolated by multiplying the cube root of the wet–bulb

measurement times the dry–bulb temperature measurement.

Answer:

A

Explanation:

A)

B)

C)

D)

49

190)

Being cooled by a fan moving room–temperature air across the body is an example of cooling by:

A)

Conduction.

B)

Convection.

C)

Radiation.

D)

Evaporation.

Answer:

B

Explanation:

A)

B)

C)

D)

191)

What would the mixed air temperature be for a system with 30 percent outdoor air if the outdoor

temperature is 20°F and the return air temperature is 70°F?

A)

(20°F + 70°F)/2 =45°F mixed air temperature

B)

0.3 × 20°F = 6°F; 0.7 × 70°F = 49°F; 6°F + 49°F = 55°F mixed air temperature

C)

0.3 × 20°F = 6°F; 6°F + 70°F = 76°F mixed air temperature

D)

Mixed air temperature cannot be calculated with the information given.

Answer:

B

Explanation:

A)

B)

C)

D)

192)

In general, which is denser: humid air or dry air?

A)

Dry air

B)

Air density peaks at 50 percent relative humidity and decreases both above and below 50

percent relative humidity.

C)

Humid air

D)

Air density is not affected by humidity.

Answer:

A

Explanation:

A)

B)

C)

D)

193)

________ is the measurement of the total heat content of the air expressed in BTU per pound of air.

A)

Dry–bulb temperature

B)

Enthalpy

C)

Latent heat

D)

Static pressure

Answer:

B

Explanation:

A)

B)

C)

D)

50

194)

The relationship of CFM and FPM can be summarized as:

A)

FPM = CFM × area.

B)

FPM = CFM.

C)

CFM = FPM/area.

D)

CFM = FPM × area.

Answer:

D

Explanation:

A)

B)

C)

D)

195)

What do technicians call the temperature at which water vapor begins to condense out of the air?

A)

Dew point

B)

Enthalpy point

C)

Wet–bulb temperature

D)

Specific humidity

Answer:

A

Explanation:

A)

B)

C)

D)

196)

________ represents the amount of water vapor in the air compared to the amount of water vapor

the air can hold.

A)

Wet–bulb temperature

B)

Relative humidity

C)

Density

D)

Specific humidity

Answer:

B

Explanation:

A)

B)

C)

D)

197)

What is the airflow through a 2 ft by 3 ft hole if the air velocity is 100 ft per minute?

A)

2 + 3 = 5 sq feet; 5 × 100 FPM = 500 CFM

B)

2 × 3 = 6 sq feet; 6 × 100 FPM = 600 CFM

C)

2 × 3 = 6 sq feet; 100 FPM/6 = 17 CFM

D)

100 CFM

Answer:

B

Explanation:

A)

B)

C)

D)

51

198)

What pressure units are used for measuring duct pressures?

A)

Psig

B)

Inches of mercury

C)

Psia

D)

Inches water column

Answer:

D

Explanation:

A)

B)

C)

D)

199)

The formula for calculating CFM is:

A)

CFM = velocity/area.

B)

CFM = FPM × 3.14.

C)

CFM = area/velocity.

D)

CFM = area × velocity.

Answer:

D

Explanation:

A)

B)

C)

D)

200)

An energy recovery ventilator:

A)

Exchanges position between the intake and exhaust air streams.

B)

Exchanges sensible heat and humidity between the intake and exhaust air streams.

C)

Exchanges sensible heat between the intake and exhaust air streams.

D)

Exchanges humidity between the intake and exhaust air streams.

Answer:

B

Explanation:

A)

B)

C)

D)

201)

Air being blown into a building with a blower is called:

A)

Infiltration.

B)

Exfiltration.

C)

Ventilation.

D)

Exhaust.

Answer:

C

Explanation:

A)

B)

C)

D)

52

202)

How many air changes per hour can a fan moving 200 CFM provide for a room with 500 sq ft of

floor space and 8–ft ceilings?

A)

1 air change

B)

12 air changes

C)

3 air changes

D)

20 air changes

Answer:

C

Explanation:

A)

B)

C)

D)

203)

A heat recovery ventilator is more energy efficient than a balanced ventilation system consisting

of an exhaust blower and a supply air blower because:

A)

It recovers energy from the attic.

B)

It recovers energy from the system blower.

C)

It recovers energy from the exhaust air.

D)

It recovers energy from the compressor.

Answer:

C

Explanation:

A)

B)

C)

D)

204)

What effect on the building pressure does a heat recovery ventilator have?

A)

No effectit is a balanced system.

B)

It decreases building pressure.

C)

It increases building pressure.

D)

It increases building pressure on one side and decreases it on the other side.

Answer:

A

Explanation:

A)

B)

C)

D)

205)

In a building, when exhaust air exceeds ventilation air, a negative pressure is created and the

difference is made up through:

A)

Duct leakage.

B)

Air leaving the building.

C)

Positive pressure.

D)

Air infiltration.

Answer:

D

Explanation:

A)

B)

C)

D)

53

206)

Air being blown out of a building with a blower is called:

A)

Infiltration.

B)

Exfiltration.

C)

Ventilation.

D)

Exhaust.

Answer:

D

Explanation:

A)

B)

C)

D)

207)

Select the characteristics of a whole–house dehumidifier. You may choose more than one.

A)

Can provide outside ventilation

B)

Must sit in the room being conditioned

C)

Does not require a drain

D)

Connects to duct system

E)

Can provide high–efficiency air filtration

Answer:

A, D, E

Explanation:

A)

B)

C)

D)

E)

208)

How can dehumidification reduce the required capacity of a mechanical cooling system?

A)

By reducing the air temperature through evaporation

B)

By precooling the air entering the evaporator

C)

By allowing the cooling system to be sized to meet just the sensible cooling load

D)

By allowing the cooling system to be sized to meet just the sensible latent load

Answer:

C

Explanation:

A)

B)

C)

D)

209)

Which type of dehumidifier has the highest operating efficiency?

A)

An atomizing dehumidifier

B)

A plate–type dehumidifier

C)

A whole–house dehumidifier

D)

A console dehumidifier

Answer:

C

Explanation:

A)

B)

C)

D)

54

210)

To avoid the creation of oxides in the refrigeration lines of mini–split systems, the lines are

assembled:

A)

Using heavy–walled flare fittings.

B)

By brazing the connections while flowing nitrogen through the lines.

C)

Using Reflok fittings.

D)

Using standard flare fittings.

Answer:

A

Explanation:

A)

B)

C)

D)

211)

Like many multisplit units, variable refrigerant flow (VRF) systems use ________ compressors and

electronic expansion valves to change the volume of refrigerant being circulated in the system.

A)

inverter driven

B)

screw

C)

reciprocating

D)

scroll

Answer:

A

Explanation:

A)

B)

C)

D)

212)

Power for the mini–split system is supplied:

A)

To the indoor and outdoor with their own separate dedicated wiring and circuit protection.

B)

To the indoor unit which powers the outdoor unit.

C)

To the outdoor unit which powers the indoor unit.

D)

Any of these methods may be used.

Answer:

C

Explanation:

A)

B)

C)

D)

213)

Typically, on mini–split systems the line set going to the outdoor unit carries ________ pressure,

________ temperature saturated liquid and vapor mix. The line going back to the outdoor unit

carries ________ pressure superheated vapor.

A)

low, low, low

B)

high, high, low

C)

low, high, high

D)

low, high, low

Answer:

A

Explanation:

A)

B)

C)

D)

55

214)

Designing a heating and cooling system to accommodate load shifts can allow buildings to

operate with ________ capacity to meet the demand.

A)

less installed

B)

more installed

Answer:

A

Explanation:

A)

B)

215)

Which system allows simultaneous heating or cooling?

A)

Multisplit system.

B)

Mini–split system

C)

Heat recovery system

Answer:

C

Explanation:

A)

B)

C)

216)

Some manufacturers recommend a ________ hour standing pressure test before evacuation.

A)

6

B)

12

C)

24

D)

2

Answer:

C

Explanation:

A)

B)

C)

D)

217)

Most multisplit units require connection to:

A)

All of the circuits.

B)

At least two indoor units, but not all of the circuits have to be used.

C)

At least four indoor units, but not all of the circuits have to be used.

D)

At least three indoor units, but not all of the circuits have to be used.

Answer:

B

Explanation:

A)

B)

C)

D)

218)

The refrigerant lines for single zone mini–split air conditioners are usually connected by:

A)

Flare fittings.

B)

SAE compression fittings.

C)

Brazed connections.

D)

Reflok fittings.

Answer:

A

Explanation:

A)

B)

C)

D)

56

219)

Before beginning the installation, the first thing the installing technician should do is:

A)

Read the installation instructions and make a list of materials.

B)

Charge their cell phone so that they can call the shop for instructions.

C)

Locate the installation instructions and put them in a safe place in case there are difficulties

with the installation that require consulting the instructions.

D)

Load up the truck with the required materials to install the system.

Answer:

A

Explanation:

A)

B)

C)

D)

220)

The main types of overcurrent protection used for a condensing unit are:

A)

Fast blowing fuses.

B)

Magnetic overload relays.

C)

Time delay fuses or an HACR circuit breaker.

D)

Condensing units do not require overcurrent protection.

Answer:

C

Explanation:

A)

B)

C)

D)

221)

Two common methods for measuring airflow in residential systems are:

A)

Fan tip speed and a fan curve plot.

B)

Temperature rise or static pressure drop.

C)

Electronic flow hoods.

D)

Velocity pressure transducers.

Answer:

B

Explanation:

A)

B)

C)

D)

57

222)

When running the primary and secondary evaporator drain lines:

A)

Always trap both drain lines.

B)

Always run the horizontal portions straight and level.

C)

Always run both drains into a common drain line to avoid reverse flow from one drain to

the other.

D)

Always run both drains separately.

Answer:

D

Explanation:

A)

B)

C)

D)

223)

A typical residential split system air conditioner consists of an:

A)

Indoor compressor and evaporator unit and an outdoor condenser coil.

B)

Outdoor condensing unit, an indoor evaporator, and an air handler.

C)

Outdoor unit containing all the refrigeration system components split into compartments

according to their function.

D)

Indoor condensing unit, an outdoor evaporator, and an air handler.

Answer:

B

Explanation:

A)

B)

C)

D)

224)

You are using the static pressure drop method to check airflow. After making an adjustment to the

system airflow, the static pressure drop across the coil increases. This indicates that:

A)

The evaporator coil became clogged during the adjustment period.

B)

The airflow has decreased.

C)

The airflow has increased.

D)

Static pressure drop is not a reliable way to check system airflow.

Answer:

C

Explanation:

A)

B)

C)

D)

58

225)

In thermostat wiring, the common industry color standard for wiring uses a white wire to control

what function?

A)

Fan relay

B)

Heating

C)

Compressor control

D)

Reversing valve

Answer:

B

Explanation:

A)

B)

C)

D)

226)

When evacuating a system after leak testing, the technician should use a micron gauge along with

the vacuum pump and pump the system down to what level?

A)

500 microns

B)

200 microns

C)

100 microns

D)

1,500 microns

Answer:

A

Explanation:

A)

B)

C)

D)

227)

When hanging flexible duct, the hanging material should be at least:

A)

2 in wide and spaced no further than every 12 ft.

B)

1 in wide and spaced no further than every 12 ft.

C)

2 in wide and spaced no further than every 5 ft.

D)

1 in wide and spaced no further than every 5 ft.

Answer:

C

Explanation:

A)

B)

C)

D)

228)

Rectangular sheet metal ducts are sealed using:

A)

General purpose duct tape.

B)

Mastic.

C)

S–locks and drives cleats.

D)

Flanges and bolts.

Answer:

B

Explanation:

A)

B)

C)

D)

59

229)

When flex duct is hung or run over long distances it must be supported every _____ft with some

sort of noncrimping hanger.

A)

5

B)

20

C)

15

D)

10

Answer:

A

Explanation:

A)

B)

C)

D)

230)

Organizations that provide duct installation standards and guidelines include:

A)

AHRI and HVAC Excellence.

B)

EPA and OSHA.

C)

Underwriters Laboratories and the National Fire Protection Association.

D)

ACCA and SMACNA.

Answer:

D

Explanation:

A)

B)

C)

D)

231)

Hangers for metal duct should be placed no further than every:

A)

12 ft.

B)

6 ft.

C)

5 ft.

D)

Sheet metal duct does not require hangers because it is self–supporting.

Answer:

A

Explanation:

A)

B)

C)

D)

232)

Which type of duct should NOT be allowed to pass through fire–rated walls?

A)

Ductboard

B)

Flexible duct connector

C)

Galvanized sheet metal duct

D)

Flexible duct

Answer:

B

Explanation:

A)

B)

C)

D)

60