<question: The density of air is
A: How much air weighs per cubic foot
B: How much volume one pound of air occupies
C: The ratio of the weight of water to that of the same volume of water
D: The ratio of the amount of water vapor contained in a cu. ft. of
A: How much air weighs per cubic foot
The specific volume of air is
A: How much air weighs per cubic foot
B: How much volume one pound of air occupies
C: The ratio of the weight of water to that of the same volume of water
D: The ratio of the amount of water vapor contained in a cu. ft. of ai
B: How much volume one pound of air occupies
The relative humidity of air is
A: The percent of moisture air is holding as opposed to the amount it could hold if it were saturated
B: Always less than 100%
C: The most accurate measurement of how much water vapor is in a given body of air
D: Used as a
A: The percent of moisture air is holding as opposed to the amount it could hold if it were saturated
As air is heated it
A: Contracts
B: Expands
C: Does not change its volume
D: Becomes more dense
B: Expands
The air pressure in a sealed balloon is
A: Static pressure
B: Velocity pressure
C: A combination of static and velocity pressures
D: None of the above
A: Static pressure
A blower connected to a length of duct
A: Creates static pressure which is then converted to velocity pressure
B: Creates velocity pressure directly
C: Creates resistance to the flow of air
D: None of the above
A: Creates static pressure which is then converted to velocity pressure
Velocity pressure is determined by
A: Subtracting static pressure from total pressure
B: Subtracting total pressure from static pressure
C: Dividing the total pressure by the static pressure
D: Subtracting the traverse pressure from the velocity
A: Subtracting static pressure from total pressure
Velocity pressure can be mathematically converted to
A: CFM
B: FPM
C: Relative humidity
D: Inches of mercury vacuum
B: FPM
fpm = 4005 x (sqrt of Vp)
An inclined manometer is basically
A: A U-tube manometer tilted at a steep angle
B: A hygrometer on a stand
C: A digital micron gauge
D: A type of sling psychrometer
A: A U-tube manometer tilted at a steep angle
A duct measures 24 inches by 18 inches. The air velocity is 600 FPM. How many CFM are being delivered through the duct? Round the number to the nearest whole number
A: 1600 CFM
B: 1800 CFM
C: 2000 CFM
D: 2200 CFM
B: 1800 CFM
V = cfm/A V = velocity in fpm
AV = (cfm/A)A A = Area in sqft
AV = cfm
3 x 600 = 1800
The static pressure of a duct is 1.76 inches and the total pressure is 2 inches. What is the velocity pressure?
A: .024 inches
B: .24 inches
C: 3.76 inches
D: zero
B: .24 inches
Tp = Sp + Vp
A pitot tube can directly measure
A: Total and velocity pressures
B: Total and static pressures
C: Velocity and static pressures
D: None of the above
B: Total and static pressures
Which of the following is the best description of a duct traverse?
A: A series of carefully spaced velocity pressure readings which may be converted to fpm using an equation
B: A series of carefully spaced velocity pressure readings which may be converted
A: A series of carefully spaced velocity pressure readings which may be converted to fpm using an equation
How many holes must be made in a round duct in order to take a series of traverse readings?
A: One
B: Two
C: Three
D: Four
B: Two
A thermo-anemometer measures
A: CFM directly
B: FPM directly
C: Total and static pressures directly
D: Temperature and humidity
B: FPM directly
The dew point temperature is
A: The temperature at which water vapor in the air will condense into a liquid
B: The temperature at which air gives up its moisture
C: The saturation temperature of water vapor in a body of air
D: All of the above
D: All of the above
Dehumidification occurs when an air conditioning coil
A: Operates at or below the dew point of the air moving across it
B: Operates above dew point
C: The cooling coil always removes moisture as long as it is operating
D: Cooling coils do not dehumidify a
A: Operates at or below the dew point of the air moving across it
Who usually determines if a duct leakage test is to be performed and the test pressure at which it will be performed?
A: The design engineer
B: The installing contractor
C: The TAB technician
D: The sheet metal foreman
A: The design engineer
When testing a duct system to determine its leakage rate, why is a special test stand necessary?
A: It contains a calibrated orifice and matching flow chart for that orifice
B: It is manufactured to accepted testing standards
C: Test results can be traced
D: All of the above
Why are two manometers mounted on a duct leakage test stand?
A: To use one as a spare in case something happens to the other
B: To be checked for accuracy against each other
C: To speed up the testing procedure
D: None of these are correct
D: None of these are correct
When the dry bulb temperature increases, the relativity humidity of air
A: Increases
B: Decreases
C: Remains the same
D: None of these
B: Decreases
When the dry bulb temperature increases, the wet bulb temperature
A: Increases
B: Decreases
C: Remains the same
D: None of these
A: Increases
When the dry bulb temperature increases, the dew point temperature
A: Increases
B: Decreases
C: Remains the same
D: None of these
C: Remains the same
When the dry bulb temperature increases, the specific humidity
A: Increases
B: Decreases
C: Remains the same
D: None of these
C: Remains the same
When the dry bulb temperature increases, the specific volume of the air
A: Increases
B: Decreases
C: Remains the same
D: None of these
A: Increases
When the dry bulb temperature increases, the density of air
A: Increases
B: Decreases
C: Remains the same
D: None of these
B: Decreases
There are _________ grains of water vapor per pound of water.
A: 0.075
B: 13.33
C: 3.42
D: 7000
D: 7000
There are _________ pounds per cubic foot of air.
A: 0.075
B: 13.33
C: 3.42
D: 7000
A: 0.075
The cfm per ton rate for normal comfort cooling is approximately
A: 250 cfm/ton
B: 300 cfm/ton
C: 400 cfm/ton
D: 500 cfm/ton
C: 400 cfm/ton
Cooling air raises its
A: Specific humidity
B: Relative humidity
C: Dew point
D: None of these
B: Relative humidity
Air with a dry bulb temperature of 60 degrees and a wet bulb temperature of 60 degrees has a relative humidity of
A: 0%
B: 50%
C: 100%
D: The answer cannot be determined without a psychrometric chart
C: 100%
Air with a dry bulb temperature of 60 degrees and a wet bulb temperature of 60 degrees has a dew point temperature of
A: 50 degrees
B: 60 degrees
C: 70 degrees
D: The answer cannot be determined without a psychrometric chart
C: 60 degrees
A sensible heat factor of 1.0 means that ________ are (is) being removed.
A: Grains
B: Water vapor
C: Moisture
D: None of these
D: None of these
Decreasing the CFM over an evaporator will _______ the moisture removal from the air.
A: Increase
B: Decrease
C: Not change
D: None of these
A: Increase
A rotating Velometer measures
A: CFM
B: FPM
C: RPM
D: Feet
D: Feet
Return air grilles are not to be installed in
A: Bedrooms
B: Bathrooms or kitchens
C: Hallways
D: Living rooms
B: Bathrooms or kitchens
The proper amount of air in CFM for each room is determined by
A: Rules of thumb
B: A detailed room-by-room heat load calculation
C: The size of the ducts
D: Local building code
B: A detailed room-by-room heat load calculation
On residential duct installations the accepted method of attaching duct sections to each other is
A: Welding them
B: Using the slip and drive method
C: The bolted flange method
D: Slip fit with a suitable sealant
B: Using the slip and drive method
Which of the following is not an acceptable location for a thermostat?
A: Five feet off the floor on an inside wall
B: Five feet off the floor on an outside wall
C: Near a return air register
D: In the most central location of the home
B: Five feet off the floor on an outside wall
What is the difference between "accuracy" and "precision" when applied to instruments?
A: Accuracy means the instrument gets the same reading each time it is used to measure the same value. Precision means the instrument is correctly calibrated.
B: Accura
B: Accuracy is a measure of how close the measurement is to being correct. Precision is the measure of how small a value the instrument can detect.
The range of an instrument is
A: The difference between the lowest and highest readings the instrument can measure
B: The smallest increment of measurement the instrument is capable of measuring
C: The difference between the cut-in and cut-out
D: The high
A: The difference between the lowest and highest readings the instrument can measure
A duct with an inside area of 4 square feet has a velocity of 1000 feet per minute. How many CFM of air are moving through that section of the duct?
A: 1000 CFM
B: 2000 CFM
C: 4000 CFM
D: 6000 CFM
C: 4000 CFM
CFM = V x A
CFM = 1000 X 4 = 4000
A 32-inch by 32-inch square duct is to be changed to a height of 28 inches so it will fit around an obstruction in a boiler room. How wide must the duct be in order to maintain the same area? Round the number off to the nearest whole number of inches.
A:
B: 37 inches
32 X 32 = H X 28
1024 = H28
1024/28 = H28/28
36.57 = H
Which of the following is not a sheet metal duct fitting?
A: Register boot
B: End boot
C: 90 degree half union
D: Starting collar
C: 90 degree half union
Which of the following is a true statement?
A: The greater the velocity, the more resistance there is to a change in direction
B: If the duct area decreases, the velocity increases
C: When a fitting creates turbulence, the turbulence continues for several
D: All of these are correct statements
Which of the following is not a duct system type?
A: Radial duct system
B: Parameter duct system
C: Extended plenum system
D: Equal friction system
D: Equal friction system
A 24-inch by 8-inch rectangular duct has an aspect ratio of
A: 1:1 ratio
B: 2:1 ratio
C: 3:1 ratio
D: 4:1 ratio
C: 3:1 ratio
The most efficient method of air balancing a duct system is
A: The equal temperature method
B: The sequential method
C: The proportional method
D: The flow hood method
C: The proportional method
Which of the following types of turning vanes produce the least dynamic system loss?
A: Single wall vanes
B: Double wall vanes
C: Heel and cheek vanes
D: Not using turning vanes at all
A: Single wall vanes
Which of the following equations is used to determine the actual operating capacity of a system?
A: BTUH = 1.08 x CFM x TD between the return and supply air
B: BTUH = 4.5 x CFM x The difference in enthalpy between the return and supply air
C: BTU = specif
B: BTUH = 4.5 x CFM x The difference in enthalpy between the return and supply air