Air System Balancing
Air System Balancing
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Question 1 |
At sea level, every square inch of the earth has an absolute pressure of _____.
A | 14.7 psia |
B | 27.68 in. w.c. |
C | 14.7 psig |
D | 1.47 psia |
Question 2 |
The formula cfm = Vk × Ak is used to calculate the _____ a given grille.
A | discharge velocity of air in fpm being delivered by |
B | air pattern for |
C | actual volume of air in cfm being discharged by |
D | velocity of output airflow for |
Question 3 |
The term standard air refers to one pound of dry air having a temperature and pressure of _____.
A | 70°F and 10.7 psia |
B | 60°F and 10.7 psia |
C | 70°F and 14.7 psia |
D | 60°F and 14.7 psia |
Question 4 |
The term that describes the horizontal divergence of an airstream after it leaves the outlet is called
the _____.
A | spread |
B | air pattern |
C | throw |
D | drop |
Question 5 |
Provided that the pressure is kept constant, Charles' law states that the volume of a gas is in direct
proportion to its _____.
A | weight |
B | absolute temperature |
C | moisture content |
D | density |
Question 6 |
The inner impact tube of a pitot tube measures _____.
A | velocity pressure |
B | cfm |
C | total pressure |
D | static pressure |
Question 7 |
The measure of the weight of air in pounds for every cubic foot of space occupied by air is called its
_____.
A | specific density |
B | specific volume |
C | atmospheric pressure |
D | absolute pressure |
Question 8 |
The lowest air pressure in an air distribution system is found at the _____.
A | blower outlet |
B | supply air diffuser |
C | return air grille |
D | blower inlet |
Question 9 |
The total heat content of an air and water vapor mixture as measured from a predetermined base is
called _____.
A | enthalpy |
B | specific heat |
C | total heat |
D | relative humidity |
Question 10 |
How many pitot tube readings should be taken on a 24" × 36" rectangular duct?
A | 12 |
B | 6 |
C | 18 |
D | 24 |
Question 11 |
A ratio expressed in percentage of the amount of moisture present in the air to the amount it can
hold at saturation at the same temperature is called _____.
A | degree of saturation |
B | specific humidity |
C | relative humidity |
D | dew point |
Question 12 |
When checking the temperature rise across the heat exchanger of a gas furnace, the temperature
rise should not exceed _____.
A | 90°F |
B | the manufacturer's recommended temperature rise range |
C | 50°F |
D | 105°F |
Question 13 |
The dew point is the _____.
A | dry-bulb temperature minus the wet-bulb temperature |
B | relative humidity at which a volume of air is totally saturated with moisture |
C | total difference in heat content between two readings in Btu/lb of air |
D | temperature at which water vapor in the air becomes saturated and starts to condense |
Question 14 |
When balancing the duct system for heating with a thermometer, take temperature readings at the
_____.
A | center of each room, about 4' above the floor |
B | supply registers, about two feet above the floor |
C | return air grilles |
D | room thermostat |
Question 15 |
The sensible heat scale on the psychrometric chart is the _____ scale.
A | dry-bulb |
B | enthalpy |
C | dew point temperature |
D | wet-bulb |
Question 16 |
When balancing an air system for cooling, the supply air volume should be between _____ cfm per
ton of cooling.
A | 250 and 400 |
B | 400 and 600 |
C | 350 and 450 |
D | 300 and 400 |
Question 17 |
Cooling a volume of air with no change in its moisture content causes the _____.
A | dew point temperature of the air to increase |
B | relative humidity of the air to remain the same |
C | relative humidity of the air to increase |
D | relative humidity of the air to decrease |
Question 18 |
When beginning to balance a system by thermometer for cooling, the supply volume dampers
should be in the _____ position.
A | one-quarter open |
B | fully open |
C | half-open |
D | closed |
Question 19 |
Velocity pressure in a duct equals the _____ pressure.
A | static pressure plus velocity |
B | total pressure minus the static |
C | total pressure minus the velocity |
D | static pressure minus total |
Question 20 |
If the speed of a blower (fan) used to move air through a distribution system is decreased, the
horsepower of the blower motor _____.
A | remains the same |
B | is decreased |
C | is increased |
D | is inversely proportional to ratio of the fan speeds |
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