Unit 10 HVAC Fundamentals

Question 1

Activated carbon will absorb odours and objectionable gases by up to \_\_\_\_\_ of its own weight before requiring replacement.  
Select one:
a. 10% 
b. 20%  
c. 30% 
d. 50%

Answer 1

b. 20%

Question 2

Air that is fully saturated has a relative humidity of:
Select one:
a. 90%
b. 96.8%
c. 100%
d. 100 grams of moisture per 100 kg of dry air

Answer 2

c. 100%

Question 3

The key criterion when designing an HVAC system is:

Select one:

a. temperature control
b. humidity control
c. air velocity
d. human health

Answer 3

d. human health

Question 4

Materials used in sheet metal ducts are:
Select one:
a. Galvanized steel and copper
b. Galvanized steel and aluminum
c. Galvanized or black steel, aluminum, copper, and stainless steel
d. Galvanized aluminum

Answer 4

c. Galvanized or black steel, aluminum, copper, and stainless steel

Question 5

Leakage from supply air ducts, when the ductwork is installed completely outside the conditioned space,
Select one:
a. Adds load to the calculated sensible heat requirements of the conditioned space
b. Adds load to the calculated latent heat load
c. Must be subtracted from the return air duct leakage
d. Must be added to the return air duct leakage

Answer 5

a. Adds load to the calculated sensible heat requirements of the conditioned space

Question 6

Which of the following units is LEAST likely to be used when measuring HVAC duct static pressure?

Select one:

a. cm of water
b. kPa
c. inches of water
d. inches of mercury

Answer 6

d. inches of mercury

Question 7

An advantage of a fully mechanical ventilation system is:
Select one:
a. It is self powered.
b. The system supplies a controlled amount of filtered and heated air.
c. The entire system only requires one fan.
d. The air is stratified, to help with filtration.

Answer 7

b. The system supplies a controlled amount of filtered and heated air.

Question 8

The dew point is the:
Select one:
a. Temperature at which water vapour will start to be absorbed into the air
b. Temperature below which water vapour will start to condense out of the air
c. Pressure below which water vapour will start to condense out of the air
d. Temperature at which water will start to evaporate

Answer 8

b. Temperature below which water vapour will start to condense out of the air

Question 9

The purpose of humidification is to:
Select one:
a. Add moisture to the air during the cooling season
b. Add moisture to the air during the heating season
c. Remove moisture from the air during the heating season
d. Remove moisture from the air during the cooling season

Answer 9

b. Add moisture to the air during the heating season

Question 10

The two general groups of fans are: 
Select one:
a. Positive displacement and dynamic 
b. High volume and low volume 
c. Positive displacement and axial flow 
d. Centrifugal and axial flow

Answer 10

d. Centrifugal and axial flow

Question 11

With respect to steam trap installations, which of the following statements is FALSE?
Select one:
a. Choose a steam trap based on the pressure difference across the trap, and a minimum capacity corresponding to three times the coil condensate rate.
b. Locate the steam trap so that its outlet is at least 30 cm above the coil condensate outlet.
c. Trap each steam coil separately.
d. Drip the steam supply main through a steam trap into the return condensate main, and not through the steam coil.

Answer 11

b. Locate the steam trap so that its outlet is at least 30 cm above the coil condensate outlet.

Question 12

Humidification in residences equipped with ducted warm air heating systems:
Select one:
a. Is not necessary because the humidity does not change with heating
b. Is accomplished by placing a single humidifier in the furnace plenum or in the warm air duct
c. Is accomplished by installing a secondary hot water heating system
d. Requires separate humidifiers for each heated area

Answer 12

b. Is accomplished by placing a single humidifier in the furnace plenum or in the warm air duct

Question 13

Calculations of return air duct leakage include:
Select one:
a. 3% seepage if the return air duct is located outside the conditioned space.
b. 3% seepage if the return air duct is located both inside and outside the conditioned space.
c. 10% leakage if the return air duct is located inside the conditioned space.
d. 3% leakage if the return air duct is located inside or outside the conditioned space.

Answer 13

a. 3% seepage if the return air duct is located outside the conditioned space.

Question 14

The propeller axial flow fan:
Select one:
a. Produces low capacity, low pressure air movement
b. Finds application in unit heaters, air-cooled condensers, and as an exhaust fan for ventilation purposes
c. Is widely used in commercial air conditioning ducting
d. Requires the least power at minimum air delivery

Answer 14

b. Finds application in unit heaters, air-cooled condensers, and as an exhaust fan for ventilation purposes

Question 15

Modulating control valves:
Select one:
a. Should be over-sized to prevent steam coil freeze-up.
b. Are mainly used for steam coils when the entering air temperature is below 1.5°C.
c. Are never used to control steam coils, regardless of inlet air temperature.
d. Are used for steam coils where the condensate must be lifted to an overhead condensate return line.
e. Can successfully control steam coils, as long as the air entering the coil is at or above 1.5°C .

Answer 15

e. Can successfully control steam coils, as long as the air entering the coil is at or above 1.5°C .

Question 16

Freezing problems in steam coils with long tube lengths, when heating large amounts of low temperature outside air, can be minimized using
Select one:
a. Preheat coils controlled by an outdoor temperature controller.
b. Modulating control valves to control the steam heating coil output.
c. A controller that fully closes the outside air dampers when the outside air temperature drops to below freezing.
d. An over-sized steam flow control valve.

Answer 16

a. Preheat coils controlled by an outdoor temperature controller.

Question 17

It is good design practice to select a steam coil size so that:
Select one:
a. 100% of the coil capacity is needed when the air temperature entering the coil is –1°C
b. At least 40% of the coil capacity is needed when the air temperature entering the coil is –1°C
c. At least 80% of the coil capacity is needed when the air temperature at the coil inlet is –1°C
d. At least 10% of the coil capacity is needed when the air temperature at the coil inlet is –5°C

Answer 17

b. At least 40% of the coil capacity is needed when the air temperature entering the coil is –1°C

Question 18

An HVAC system is a ___________ system.

Select one:

a. Humidifying, Ventilating, Air Conditioning and Cooling system
b. Humidification, Ventilation, Air filtration, and Conveying system
c. Heating, Ventilation, and Air Conditioning system
d. Heating, Ventilating, Air movement, and Cooling system

Answer 18

c. Heating, Ventilation, and Air Conditioning system

Question 19

Steam coils with long tube lengths:
Select one:
a. Are likely to freeze when the incoming air is extremely cold (say -35°C)
b. Have the greatest freezing problems at temperatures approaching –2°C.
c. Cause overheating and poor set point tracking during cold weather
d. Are unlikely to freeze at any temperature.

Answer 19

b. Have the greatest freezing problems at temperatures approaching –2°C.

Question 20

Which one of the following air cleaning devices can be used for the removal of gases and vapour? 
Select one:
a. Air washers 
b. Electronic air cleaners 
c. Charcoal absorbers  
d. Air sterilizers

Answer 20

c. Charcoal absorbers

Question 21

A buried ventilation duct in an older building draws air from a chemistry lab fume hood. The duct would likely be constructed of
Select one:
a. Galvanized steel sheet metal
b. Aluminum sheet metal
c. Cement asbestos 
d. Fiberglass

Answer 21

c. Cement asbestos

Question 22

One of the advantages of a common exhaust duct system used for ventilation in a large building is:
Select one:
a. There is no fan to maintain
b. The building can be maintained at a slight negative pressure at all times.
c. There is only one fan to maintain
d. The building can be kept odour-free

Answer 22

c. There is only one fan to maintain

Question 23

Electronic air cleaners are divided into ____________ classes.
Select one:
a. Commercial and residential
b. High voltage and low voltage
c. Electrostatic precipitators and charged media electronic
d. AC and DC

Answer 23

c. Electrostatic precipitators and charged media electronic

Question 24

Very low humidity causes
Select one:
a. increased perspiration
b. static electricity build-up 
c. headaches
d. wooden furniture and hardwood floors to swell

Answer 24

b. static electricity build-up

Question 25

Wet-bulb temperature is:
Select one:
a. The temperature indicated by a thermometer whose bulb covered by a water-wetted wick, and exposed to a rapidly moving stream of air
b. The dew point temperature
c. Always less than the dry-bulb temperature
d. The product of the dry-bulb temperature times the relative humidity.

Answer 25

a. The temperature indicated by a thermometer whose bulb covered by a water-wetted wick, and exposed to a rapidly moving stream of air

Question 26

Bacteria can range from_____________ in size.

Select one:

a. 150 to 1000 microns
b. 0.2 to 0.3 microns
c. 0.2 to 5 microns
d. 5 to 150 microns

Answer 26

c. 0.2 to 5 microns

Question 27

Ultraviolet light is used to remove \_\_\_\_\_ from the air. 
Select one:
a. Dust and pollen 
b. Fine dust and smoke 
c. Bacteria  
d. Mists and fogs

Answer 27

c. Bacteria

Question 28

Which of the following is NOT a type of centrifugal fan?
Select one:
a. Forward curved fan wheel
b. The propeller fan
c. The radial blade fan
d. The backward inclined airfoil blade fan

Answer 28

b. The propeller fan

Question 29

In a a system with mechanical air intake and natural exhaust ventilation, the building static pressure is maintained
Select one:
a. Slightly below atmospheric pressure 
b. At atmospheric pressure 
c. Slightly above atmospheric pressure  
d. Well above atmospheric pressure

Answer 29

c. Slightly above atmospheric pressure

Question 30

Air duct velocity pressure is measured by connecting a:
Select one:
a. Manometer to the side of an air duct
b. Bourdon tube to the air duct
c. Pressure gauge to the side of a duct, with a sensing tube extending inside of the duct directed toward the airflow
d. Manometer to the side of a duct, with a sensing tube extending inside of the duct directed toward the airflow

Answer 30

d. Manometer to the side of a duct, with a sensing tube extending inside of the duct directed toward the airflow

Question 31

The residential humidifier which is commonly used in the supply plenum of smaller warm air furnaces and consists of a shallow tray partially filled with water is called a: 
Select one:
a. Bypass humidifier
b. Wetted element humidifier
c. Pan type humidifier 
d. Power type humidifier

Answer 31

c. Pan type humidifier

Question 32

Which of the following is NOT a common complaint related to HVAC system operation?

Select one:

a. the air is too humid or too dry
b. rooms are too hot or too cold
c. the smell of too much perfume or cologne
d. too much or too little air movement

Answer 32

c. the smell of too much perfume or cologne

Question 33

Backward inclined centrifugal fans:
Select one:
a. Require more horsepower than the forward curved fans to deliver a specified volume of air
b. Are quieter than forward curved fans
c. Are less efficient than forward curved fans
d. Are noisier than forward curved fans

Answer 33

b. Are quieter than forward curved fans

Question 34

Viscous impingement filters are highly efficient in the removal of:
Select one:
a. Fine dust, fumes, and smoke 
b. Bacteria and spores 
c. Cooking odours 
d. Dust and pollen

Answer 34

d. Dust and pollen

Question 35

The static pressure measured in an air duct is measured by connecting a:
Select one:
a. Manometer to the side of an air duct
b. Bourdon tube to the air duct
c. Pressure gauge to the side of a duct, with a sensing tube extending inside of the duct directed toward the airflow
d. Manometer to the side of a duct, with a sensing tube extending inside of the duct directed toward the airflow

Answer 35

a. Manometer to the side of an air duct

Question 36

Air conditioning ducts are classified as:
Select one:
a. Low pressure, medium pressure, and high pressure
b. Fire resistant and flame-suppressing
c. Light, medium, and heavy gauge
d. Heating and cooling

Answer 36

a. Low pressure, medium pressure, and high pressure

Question 37

Total pressure exerted by the air is the sum of:
Select one:
a. Static suction lift and static discharge head
b. Head pressure and suction pressure
c. Static pressure and velocity pressure
d. Suction pressure and velocity pressure

Answer 37

c. Static pressure and velocity pressure

Question 38

Humidifying units that force warm air through a wet pad, and return the air to the room, are called: 
Select one:
a. Pan type humidifiers with plates 
b. Atomizing humidifiers 
c. Bypass type humidifiers 
d. Wetted element humidifiers

Answer 38

d. Wetted element humidifiers

Question 39

Air ducts of large dimensions must be diagonally creased
Select one:
a. To provide stiffness
b. To allow expansion and contraction
c. To increase air velocity
d. To decrease air friction in the duct work

Answer 39

a. To provide stiffness

Question 40

Which of the following is an advantage of medium and high pressure HVAC duct systems?
Select one:
a. Lower operating cost
b. No need for costly noise suppression devices
c. Less costly fabrication and installation
d. Less physical space requirements

Answer 40

d. Less physical space requirements