Mechanical Engineering Unit 71 To 80 What Should Always Running When The Chiller Operating Chilled Air Handler Fan

154)

What should always be running when the chiller is operating?

A)

Chilled air–handler fan

B)

Cooling tower fan and damper

C)

Mixed–air damper outlet

D)

Condenser–cooling water pump

Answer:

D

Explanation:

A)

B)

C)

D)

155)

What does the low–temperature thermostat do?

A)

It controls steam flow through the preheat coil.

B)

It starts the system when the temperature outside reaches 35°F.

C)

It controls the flow of chilled water through the coil.

D)

When it senses air temperature below 35°F, it shuts down the blower.

Answer:

D

Explanation:

A)

B)

C)

D)

156)

Why does compressed air require a dryer?

A)

Compressing air tends to cool it off, causing water to begin condensing.

B)

To remove residual moisture that may have entered the air lines during installation

C)

To dehumidify the air

D)

Some small amounts of water from the water jacket cooling the air compressor enter the

compressed air.

Answer:

C

Explanation:

A)

B)

C)

D)

157)

Control valves used for steam heating coils are typically:

A)

Four–way valves.

B)

Three–way valves.

C)

Either two–way or three–way valves.

D)

Two–way valves.

Answer:

D

Explanation:

A)

B)

C)

D)

41

158)

An undersized valve may cause:

A)

Cycling.

B)

Trickling.

C)

Cavitation.

D)

Hunting.

Answer:

C

Explanation:

A)

B)

C)

D)

159)

A two–way control valve reduces the flow through the coil by:

A)

Opening and closing in pulses to vary the flow.

B)

Allowing some of the flow to bypass the coil.

C)

Closing and reducing the flow through the circuit.

D)

Sending some of the flow backwards in the direction it came from.

Answer:

C

Explanation:

A)

B)

C)

D)

160)

The humidity sensor is used to adjust what components?

A)

The heating coil face and bypass dampers

B)

The cooling coil face and bypass dampers

C)

The cooling coil face and air–mixing dampers

D)

The heating coil face and air–mixing dampers

Answer:

B

Explanation:

A)

B)

C)

D)

161)

Control valves used for water coils are typically:

A)

Three–way valves.

B)

Either two–way or three–way valves.

C)

Two–way valves.

D)

Four–way valves.

Answer:

B

Explanation:

A)

B)

C)

D)

42

162)

What is an opaque surface?

A)

A surface that is highly reflective

B)

A surface that light can pass through, such as windows

C)

A surface that air cannot pass through

D)

A surface that light cannot pass through, such as walls

Answer:

D

Explanation:

A)

B)

C)

D)

163)

How is an HTM calculated?

A)

U value times the temperature difference

B)

Average material R value times the temperature difference

C)

Add the R values.

D)

Add the R values of the different materials and then find the reciprocal.

Answer:

A

Explanation:

A)

B)

C)

D)

164)

In selecting the outside cooling design conditions for Manual J8, a temperature is chosen for each

area that:

A)

Is exceeded 1% of the year.

B)

Represents an average of the outdoor temperature during the cooling season.

C)

Is the highest recorded temperature for that area.

D)

Is based on the geographical latitude of the area.

Answer:

A

Explanation:

A)

B)

C)

D)

165)

What is the difference between heat loss and heat gain?

A)

Heat loss occurs in the summer, and heat gain occurs in winter.

B)

Heat loss occurs in well insulated houses, and heat gain occurs in poorly insulated houses.

C)

Heat loss occurs in poorly insulated houses, and heat gain occurs in well insulated houses.

D)

Heat loss occurs in the winter, and heat gain occurs in summer.

Answer:

D

Explanation:

A)

B)

C)

D)

43

166)

What is the most common residential load calculation that is accurate?

A)

ACCA Manual J

B)

Dividing the house volume by an air change factor, such as 20

C)

Multiplying the number of rooms ×

4,000

D)

Dividing the floor area by a load factor, such as 600 ft2 per ton

Answer:

A

Explanation:

A)

B)

C)

D)

167)

What effect does the daily range have on heat gain?

A)

Areas with a high daily range experience higher temperatures, so the cooling HTMs are

higher.

B)

Areas with a high daily range generally require equipment with more latent cooling

capacity.

C)

Areas with a high daily range can take advantage of natural cooling that occurs at night, so

the cooling HTMs can be a little smaller.

D)

Areas with a high daily range generally do not require any cooling.

Answer:

C

Explanation:

A)

B)

C)

D)

168)

In selecting the outside heating design conditions for Manual J8, a temperature is chosen for each

area that:

A)

Represents an average of the outdoor temperature during the heating season.

B)

Is based on the geographical latitude of the area.

C)

Is exceeded 99 percent of the year.

D)

Is the lowest recorded temperature for that area.

Answer:

C

Explanation:

A)

B)

C)

D)

44

169)

When performing an initial system check, a TAB technician determines that the total airflow the

blower is moving cannot be adjusted to meet design specifications. This could indicate that:

A)

There is too much restriction in the ductwork.

B)

There is no air filter installed.

C)

There are leaks in the supply–side ductwork.

D)

There are leaks in the return–side ductwork.

Answer:

A

Explanation:

A)

B)

C)

D)

170)

Why is testing and balancing an important part of HVACR residential systems?

A)

Because all new home construction must be certified

B)

Because HVACR systems are the largest energy appliances in a residence and energy costs

have increased

C)

Because it is the first and last step a technician must perform when working on HVACR

systems

D)

Because HVACR systems are not as efficient as they were in earlier decades

Answer:

B

Explanation:

A)

B)

C)

D)

171)

Contractors and technicians performing TAB services typically require certification by an

independent TAB standards and certification organization such as:

A)

AHRI or GAMA.

B)

The EPA or DOE.

C)

UL or CSA.

D)

NEBB or AABC.

Answer:

D

Explanation:

A)

B)

C)

D)

45

172)

Instruments that can read the pressure in a duct system include:

A)

Tachometer, anemometer, and magnehelic gauge.

B)

Inclined manometer, magnehelic gauge, and digital manometer.

C)

Inclined manometer, compound gauge, and U–tube manometer.

D)

U–tube manometer, compound gauge, and tachometer.

Answer:

B

Explanation:

A)

B)

C)

D)

173)

The main advantage of measuring airflow using the temperature rise method is that temperature

rise measurements:

A)

Can be taken easily using a common thermometer.

B)

Require no calculation.

C)

Work well in both the heating and cooling cycles.

D)

Are more accurate than measurements taken with a flow hood.

Answer:

A

Explanation:

A)

B)

C)

D)

174)

What is done when an HVACR system is commissioned?

A)

The system is named.

B)

The system is started for the first time.

C)

The system is checked to make sure it is operating as designed.

D)

The system is designed.

Answer:

C

Explanation:

A)

B)

C)

D)

46

175)

A TAB technician determines that the total airflow leaving the supply registers is much lower

than the amount of air the blower is moving. This indicates that:

A)

There is too much restriction in the return–side ductwork.

B)

There are leaks in the return–side ductwork.

C)

There is too much restriction in the supply–side ductwork.

D)

There are leaks in the supply–side ductwork.

Answer:

D

Explanation:

A)

B)

C)

D)

176)

The volume of air flowing out a supply register can be directly measured with a(n):

A)

Anemometer.

B)

Flow hood.

C)

Tachometer.

D)

Velometer.

Answer:

B

Explanation:

A)

B)

C)

D)

177)

How is a velometer used to determine the CFM at a supply register?

A)

The average air velocity is the same thing as CFM.

B)

The average air velocity is multiplied by 1.08.

C)

The average air velocity is multiplied by the face area of the register.

D)

The average air velocity is multiplied by the free area of the register.

Answer:

D

Explanation:

A)

B)

C)

D)

178)

Industrial refrigeration is primarily concerned with cooling processes and machines in

manufacturing:

A)

Homes and dwellings.

B)

Food products in grocery stores.

C)

Large retail buildings.

D)

Processes and machines in manufacturing.

Answer:

D

Explanation:

A)

B)

C)

D)

47

179)

Commercial air conditioning refers to air–conditioning applications in:

A)

Private homes and apartments.

B)

Food and product storage.

C)

Automobiles and trucks.

D)

Retail stores and office buildings.

Answer:

D

Explanation:

A)

B)

C)

D)

180)

Semihermetic compressors on large commercial AC units use ________ to stage the compressor by

cutting out individual cylinders in response to load changes.

A)

king valves

B)

automatic expansion valves

C)

unloaders

D)

TXV valves

Answer:

C

Explanation:

A)

B)

C)

D)

181)

Glycol solutions are added to water in secondary refrigerant loops:

A)

To lubricate the circulating pump bearings.

B)

To increase the system heat transfer.

C)

To make leaks easier to locate.

D)

To prevent freezing and inhibit corrosion.

Answer:

D

Explanation:

A)

B)

C)

D)

182)

One advantage of rooftop units on small commercial buildings is that:

A)

They are available in larger capacities than central station systems.

B)

They are easier to service than systems located inside the building.

C)

They operate more efficiently than systems located inside the building.

D)

They offer a substantial savings of space within the building.

Answer:

D

Explanation:

A)

B)

C)

D)

48

183)

What applications are best suited for console through the wall PTAC units?

A)

Hotels and motels

B)

Grocery stores

C)

Sound recording studios

D)

Large retail stores

Answer:

A

Explanation:

A)

B)

C)

D)

184)

Compressor capacity can be controlled by:

A)

Discharge valve throttling.

B)

Voltage or current modulation.

C)

Blocking the discharge gas with a solenoid.

D)

Cylinder unloading or hot gas bypass.

Answer:

D

Explanation:

A)

B)

C)

D)

185)

What is a DX coil?

A)

A direct expansion coil

B)

A direct extension coil

C)

A digital extension coil

D)

A digital expansion coil

Answer:

A

Explanation:

A)

B)

C)

D)

186)

Airflow through an axial fan is:

A)

At a 45° angle to the fan shaft.

B)

From the inside of the fan blade outwards in a radial pattern.

C)

Perpendicular to the fan shaft.

D)

Parallel to the fan shaft.

Answer:

D

Explanation:

A)

B)

C)

D)

49

187)

Poorly maintained humidifiers can become indoor air quality concerns because of:

A)

Increased outgassing of volatile organic compounds.

B)

Unintended chemical reactions with HFC refrigerants.

C)

Mold and mildew growth.

D)

Increased static discharge around all electrical connections.

Answer:

C

Explanation:

A)

B)

C)

D)

188)

Where are unit ventilator fan coil units installed in schools?

A)

On the roof above each classroom

B)

Below window level in each classroom

C)

Outside each classroom on a concrete pad

D)

In the school mechanical room

Answer:

B

Explanation:

A)

B)

C)

D)

189)

AMCA fan performance classifications are based on:

A)

Minimum and maximum fan RPM for the design airflow.

B)

The upper and lower ranges of static pressure and outlet velocity.

C)

The physical design of the fan wheel.

D)

The minimum and maximum motor horsepower.

Answer:

B

Explanation:

A)

B)

C)

D)

190)

What is an “air–over” motor?

A)

A motor whose function is to blow air over the fan motor to cool it

B)

A motor that is designed to be installed on the bottom of a fan unit

C)

A motor that is designed for units with the fan located at the top of the unit

D)

A motor that is cooled by airflow over the motor

Answer:

D

Explanation:

A)

B)

C)

D)

50

191)

Why should ultraviolet germicidal lamps NOT be handled with bare hands?

A)

The residual UV in the lamp coating can cause severe burns.

B)

The oil from your fingerprints can lead to premature failure of the lamp.

C)

The exterior UV coating will wipe off, reducing the UV output.

D)

The coating on the outside of the lamp is toxic.

Answer:

B

Explanation:

A)

B)

C)

D)

192)

The major components of an air–handling unit include:

A)

Air compressor, water separator, and air tank.

B)

Heating and cooling coils and electric heat strips.

C)

Compressor, evaporator, and condenser.

D)

Fan and motor, heating and cooling coils, air filter, dampers.

Answer:

D

Explanation:

A)

B)

C)

D)

193)

What type of blower configuration requires a water–filled P–trap to ensure proper condensate

draining?

A)

No P–trap is needed on rooftop installations.

B)

Draw–through evaporator with blower downstream

C)

Push–through evaporator with blower upstream

D)

Blower configuration does not affect drainage.

Answer:

B

Explanation:

A)

B)

C)

D)

51

194)

Codes relating to rooftop installation include:

A)

Uniform Mechanical code, International Mechanical code, and National Fuel Gas code.

B)

NIST, UL, and CSA.

C)

International Conditioned Air Code, Rooftop Installation National Code, and International

Heating & Cooling Code.

D)

OSHA, DOE, and EPA.

Answer:

A

Explanation:

A)

B)

C)

D)

195)

Gas–fired rooftop units are normally vented through:

A)

A separate power venter.

B)

Draft hoods connected directly to the unit.

C)

Double–wall vent pipe connected to the top of the unit.

D)

Double–wall vent pipe connected to the side of the unit.

Answer:

B

Explanation:

A)

B)

C)

D)

196)

Proper height above the roof is important when installing a heat pump rooftop unit:

A)

So that snow does not block airflow through the outdoor coil.

B)

To allow the condenser to take advantage of local prevailing wind.

C)

To ensure adequate combustion air to the burners.

D)

So that the unit can be serviced from underneath.

Answer:

A

Explanation:

A)

B)

C)

D)

197)

The raised, rectangular sheet metal frame that a rooftop unit rests on is called a:

A)

Curb.

B)

Pad.

C)

Frame.

D)

Fixture.

Answer:

A

Explanation:

A)

B)

C)

D)

52

198)

The gas line should include:

A)

A flexible connector and a stop valve.

B)

A stop valve and a drip leg.

C)

A stop valve.

D)

A gas filter and a drip leg.

Answer:

B

Explanation:

A)

B)

C)

D)

199)

Which part of a large office building generally requires cooling all year, even when it is cold

outside?

A)

Perimeter

B)

Core

C)

Top floor

D)

Bottom floor

Answer:

B

Explanation:

A)

B)

C)

D)

200)

Which of the following statements is most accurate?

A)

Perimeter systems accommodate many of the loads of the core system and loads caused by

weather.

B)

Core systems must adjust to accommodate variables such as wind effects.

C)

Core systems are subject to a wider range of variables than perimeter systems.

D)

Perimeter systems only need to accommodate loads such as electrical equipment and

lighting.

Answer:

A

Explanation:

A)

B)

C)

D)

201)

The core of a large multistory high–rise building consists of:

A)

The interior areas.

B)

The most important areas.

C)

The areas around the outside of the building.

D)

The main floors.

Answer:

A

Explanation:

A)

B)

C)

D)

53

202)

In the event of a fire, fire dampers prevent oxygen from feeding the fire by:

A)

Spraying suppressant foam.

B)

Limiting the amount of outside air to 10 percent.

C)

Removing all oxygen from the space.

D)

Closing off the outside air supply completely.

Answer:

D

Explanation:

A)

B)

C)

D)

203)

How does an energy–recovery wheel transfer latent heat between the ventilation and exhaust air?

A)

The desiccant in the wheel absorbs moisture in the air.

B)

The wheel spins very fast.

C)

An absorption cycle

D)

A compression cycle

Answer:

A

Explanation:

A)

B)

C)

D)

204)

When a VAV box on a constant–air–volume system throttles air into the conditioned area:

A)

The compressor and blower both slow down to match.

B)

The excess air dumps into the area above the ceiling.

C)

The compressor slows down to match it.

D)

The blower slows down to reduce overall airflow.

Answer:

B

Explanation:

A)

B)

C)

D)

205)

The design pressure drop across the valve is measured when the valve is:

A)

Fully open.

B)

Fully closed.

C)

Removed.

D)

Installed.

Answer:

A

Explanation:

A)

B)

C)

D)

54

206)

A three–way control valve reduces the flow through the coil by:

A)

Closing and reducing the flow through the circuit.

B)

Sending some of the flow backwards in the direction it came from.

C)

Opening and closing in pulses to vary the flow.

D)

Allowing some of the flow to bypass the coil.

Answer:

D

Explanation:

A)

B)

C)

D)

207)

Which control system allows a building to be monitored and controlled from a remote location?

A)

Pneumatic

B)

Piezoelectric

C)

Direct digital

D)

Electronic

Answer:

C

Explanation:

A)

B)

C)

D)

208)

What regulates the flow of chilled water through the cooling coil?

A)

The input temperature

B)

The condenser

C)

A control valve

D)

An electric fan

Answer:

C

Explanation:

A)

B)

C)

D)

209)

A device that converts a nonelectrical impulse such as sound, heat, light, or pressure into an

electrical signal is called:

A)

A sensor.

B)

A sending unit.

C)

A switch.

D)

An actuator.

Answer:

A

Explanation:

A)

B)

C)

D)

55

210)

What types of compressors are commonly used for large chillers?

A)

Rotary and reciprocating

B)

Rotary and scroll

C)

Diaphragm and bellows

D)

Centrifugal and screw

Answer:

D

Explanation:

A)

B)

C)

D)

211)

Hot water is circulated through a hot water heating system:

A)

Using large diaphragm pumps.

B)

Using external–drive water compressors.

C)

Because of the density difference between hot and cold water.

D)

Using water circulating pumps.

Answer:

D

Explanation:

A)

B)

C)

D)

212)

Many central system chillers use water–cooled condensers because:

A)

Air–cooled condensers contribute more to global warming.

B)

The compressor can be located almost anywhere inside the building.

C)

Water–cooled condensers require less maintenance than air–cooled condensers.

D)

Water–cooled chillers take up less space inside the building than air–cooled chillers.

Answer:

B

Explanation:

A)

B)

C)

D)

213)

Coil corrosion that results from two dissimilar metals coming in contact with an electrolyte is

called:

A)

General corrosion.

B)

Electrolytic.

C)

Hygroscopic.

D)

Galvanic.

Answer:

D

Explanation:

A)

B)

C)

D)

56

214)

What does hygroscopic mean?

A)

It refers to a method of growing plants in water without soil.

B)

A material that readily absorbs water is hygroscopic.

C)

A percentage moisture measurement taken with a hygroscope is referred to as the

hygroscopic index.

D)

A material that is totally incompatible with water is hygroscopic.

Answer:

B

Explanation:

A)

B)

C)

D)

215)

A central station air–handling unit:

A)

Combines the functions of the evaporator blower and the condenser blower.

B)

Is used for large systems and is assembled on site using separate components.

C)

Consists of a fan and coil and usually handles a single room or zone.

D)

Is used instead of a fan and fan motor.

Answer:

B

Explanation:

A)

B)

C)

D)

216)

A type of fan that is designed for producing high static pressure in a duct distribution system is:

A)

Impeller.

B)

Centrifugal.

C)

Condenser.

D)

Axial.

Answer:

B

Explanation:

A)

B)

C)

D)

217)

The two basic types of fans used in most air–handling units are:

A)

Positive pressure and negative pressure.

B)

Reciprocating and orbital.

C)

Clockwise rotating and counterclockwise rotating.

D)

Centrifugal and axial.

Answer:

D

Explanation:

A)

B)

C)

D)

57

218)

The most common fan used for moving air through ductwork in residential air conditioning is:

A)

Propeller.

B)

Vane axial.

C)

Forward–curved centrifugal.

D)

Backward–curved centrifugal.

Answer:

C

Explanation:

A)

B)

C)

D)

219)

The location for a rooftop unit will be partly determined by:

A)

The clearest path available for sliding the unit across the roof.

B)

The availability of anchor points for attaching the drag winch.

C)

The easiest place to cut a hole in the roof.

D)

The distance that a crane can reach over the edge of the building.

Answer:

D

Explanation:

A)

B)

C)

D)

220)

One unique problem with rooftop units installed in a seacoast area is that:

A)

Systems with a high sensible capacity are required because of the low humidity in coastal

areas.

B)

The prevailing winds reduce the cooling capacity of the condenser.

C)

Codes in coastal areas typically require a minimum 3 ft ground clearance to allow for

flooding.

D)

Salt spray accelerates corrosion of metallic parts.

Answer:

D

Explanation:

A)

B)

C)

D)

221)

PVC drain lines on rooftop units should be insulated:

A)

To reduce the sound created by the high velocity through the drain.

B)

To improve system efficiency.

C)

To prevent deterioration of the PVC from exposure to UV.

D)

To avoid heating the condensate water.

Answer:

C

Explanation:

A)

B)

C)

D)

58