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76 Cards in this Set
- Front
- Back
- 3rd side (hint)
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One reason for using a reducing plenum system is to keep |
D. both A and C |
A. The velocity of the air constant B. The noise level low C. The duct pressure constant D. both A and C |
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By design which of the following air ducts will allow 312.5 CFM to flow with a velocity of 500 FPM |
C. 10"x 9" |
A. 9"x 8" B. 16"x 9" C. 10"x 9" D. None of the above |
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Technician "A" says that if the air filter on the air conditioning system is totally blocked with dirt, the amperage draw on the evaporator fan will go down. Technician "B" says that if you close down one Supply register on a duct system, the volume of the air feeding the locations will increase slightly. Which of the following statements is correct? |
Technician A is correct. Technician B is correct. |
A. Technician A is correct, technician B is correct B. Technician A is correct, technician B is incorrect C. Technician A is incorrect, technician B is correct D. Technician A is incorrect, technician B is incorrect |
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If the length of a transition piece of ductwork is 10 feet and the main duct in the series with it is 20 feet what is the length used to estimate the total frictional losses |
Not enough information |
A. 10 feet B. 30 feet C. 60 feet D. Not enough information |
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The pressure in a duct system is measured in |
WC |
A. PSIG B. PSIA C. "HG D. "WC |
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Measuring velocity pressure in a duct indicates the |
Speed at which the air is moving |
A. Volume of air through a duct B. Speed at which the air is moving C. Pressure against the sides of the duct D. Weight of the air moving through the duct |
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If the resistance against a centrifugal blower is doubled the CFM output decreases and the amperage draw of the motor |
Decreased slightly |
A. Decreases slightly B. Increased slightly C. Stays the same D. Overheats the motor |
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If the resistance against a propeller fan is doubled the CFM output decreases but the amperage draw of the motor |
Increases |
A. Decreases B. Increases C. Stays the same D. Overheats the motor |
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Which of the following is typically measured with an inclined water manometer |
Static pressure in a duct system |
A. Static pressure in a duct system B. Pressure in a refrigeration system C. Manifold pressure in a gas-fired furnace D. Nozzle pressure of an oil burner |
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The reason for using a reducing extended plenum system is to |
Maintain a more even pressure throughout the entire length of the trunk duct |
A. Save metal by using a smaller duct B. Reduce the operating costs of the system C. Provide easier means of fastening the take-off fittings D. Maintain a more even pressure throughout the entire length of the truck duct |
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The fitting at the end of a round duct that connects the duct to the floor register is called a(n) |
End boot |
A. End boot B. Reducer C. Take off D. Stack head |
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One ton of air conditioning is equal to |
288000 BTUs/24 hours |
A. 288000 BTU / 24 hours B. 12000 BTU C. 1200 BTU / hour D. 12000 BTU / 24 hours |
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An example of PPE is |
All of the above |
A. Hearing protection B. Safety glasses C. Gloves D. All of the above |
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A magnehelic gauge can register |
All of the above |
A. Static pressure B. Velocity pressure C. Total pressure D. All of the above |
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Two types of conditioning systems are |
Both A and B |
A. Forced convection B. Natural draft C. Both A and B D. None of the above |
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True or false: When a canvas collar(vibration eliminator) is properly installed between 2 duct sections, the metal surfaces of the duct work should be rubbing against each other. |
False |
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True or false: Ideally, the sum of all the air volumes feeding each area of a conditioned space should equal the tonnage of the system multiplied by 400 |
True |
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True or false: the volume of air that an air-conditioning system can deliver can be increased by adjusting the belt tension on the blower |
False |
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True or false: to put trunk duct or extended plenum sections together, the device used is called a drive clip |
True |
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True or false: because the blower in the air handler (furnace) draws the air down the return air duct system, the return air duct is the same size as the supply duct system |
False |
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The static pressure in a duct is the total pressure less the velocity pressure |
True |
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True or false: The free area of most registers and grills is 65% of the total face area |
True |
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True or false: fpm indicates Air volume |
False |
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True or false: CFM indicate Air volume |
True |
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True or false: air has weight |
True |
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In a typical air conditioning system, _______ CFM of air is moved through the evaporator for each 12000 BTU/hour cooling capacity of the system |
400 |
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In a residential air conditioning system, the only air moving device that is used as a |
Squirrel cage |
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To connect a branch duct to the main duct a _______ fitting is used |
Take off |
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Blower assembly utilize to drive mechanisms _______ & _______ |
Direct drive, belt |
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Name two devices for measuring air velocity |
Pilot tube, velometer |
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List four components that make up the forced air system |
Blower, return air, Air Supply, Grill and register |
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Brant's books should always use what component to balance the air to the individual areas |
Pampers |
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Which type of fan creates more pressure from Inlet to outlet and is more desirable for a commercial duct system |
Forward centrifugal type |
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A duct system is pressurized by what three pressures |
Static, velovity, total |
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Why is inches of water column used to measure duct pressure instead of PSIG |
Largest scales can't accurately measure duct pressure |
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When a filter rack return Grill is located in the living space why is it a good idea to make the return duct as large as possible |
Larger the duct suiter the air |
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A 24 foot by 37 foot single story house with a basement has the heating unit in one end of the basement. What type of supply duct system would be used in this application |
Reduced extended plenum |
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A home on a concrete slab has a Perimeter Loop air distribution system. What is the important advantage of this system over an overhead system |
Warmer Air at the perimeter |
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When is insulation required on air ducts |
If air is 15 degrees different from air inside duct or unconditioned air |
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What would be your layout measurements for a piece of duct that is 20"x 32" by 42". The duck will be made in two pieces and have raw edges on both ends |
52 1/4" x 42" |
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Name a form of natural draft Heating |
Baseboard water heater |
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Describe forced convection heating cooling |
Use the blower to move air over the conditioned equipment |
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One drawback of using custom made, premeasured duct sections is that |
All of the above |
A. If the measuring was not done correctly, the job may not go together B. the sharp edges provide possibly possible safety issues C. altering a duck section at the job site is extremely cost-ineffective D. all of the above |
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The reason meaning installations utilize that straight main trunk line with flexible duct rides to the individual register boots size 2 |
All of the above |
A. Eliminate the expense of custom-made duck sections B. reduce excessive noise C. speed up the installation process D. all of the above |
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What two Fasteners are used with sheet metal square and rectangular duct |
"S" Fasteners (clips) and drive Clips (cleats) |
A. "S" Fasteners (clips) and drive Clips (cleats) B. Staples and tape C. self tapping screws and draw bands D. tabs and adhesives |
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What Fastener is commonly used with round flexible duct |
Self tapping screws and draw bands |
A. "S" Fasteners (clips) and drive Clips (cleats) B. Staples and tape C. self tapping screws and draw bands D. tabs and adhesives |
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What two factors are used with fiberglass duct |
Staples and tape |
A. "S" Fasteners (clips) and drive Clips (cleats) B. Staples and tape C. self tapping screws and draw bands D. tabs and adhesives |
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A good way to fasten insulation to the inside of sheet metal duct is to use |
Tabs and adhesive |
A. "S" Fasteners (clips) and drive Clips (cleats) B. Staples and tape C. self tapping screws and draw bands D. tabs and adhesives |
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A trap in the condensate line prevents |
All of the above |
A. Air and foreign material from being drawn up in the drain line B. additional cooling load from warm air drawn up into the air handler C. insect invasion of the system D. all of the above |
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an auxiliary drain pan under an air handler is required when the air handler is installed |
All of the above |
A. In an attic B. in a drop ceiling C. above a traffic area D. all of the above |
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A boot in a duct system is used |
Between the branch duct and the register |
A. At the plenum B. between the truck duct and the branch duct C. between the branch duct and the register D. to eliminate vibration between the unit in the duct |
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After refrigerant lines have been installed, they should be evacuated to a pressure of |
500 microns |
A. 28" vacuum B. 28" vacuum C. 5000 microns D. 500 microns |
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True or false: the purpose of a canvas connector in a duct system is to reduce the transmission of noise and vibration |
True |
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True or false when installing a split air conditioning system with a remote condensing unit, the liquid line, suction line, and low voltage wire can be bundled together and run as a single piece from the condensing unit to the air handler |
Truth |
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Once the power has been connected to the condensing unit, it is a good idea to start the compressor immediately to make certain it runs |
False |
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When hanging a horizontal air handler, it should be pitched toward the drain port for proper condensate removal |
False |
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Lining a piece of duct is accomplished by using tabs and washers and/or glue |
True |
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The sun shining on the outdoor section of the air conditioning system has a direct affect on the operation of the unit |
False |
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Power to the control transformer is controlled by the conditioned area thermostat |
False |
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The halide torch will only detect products containing halogen compounds |
False |
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A halide leak detector will find a leak less than .5 oz per year |
False |
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Before a system is evacuated, all piping should be |
Checked for leaks |
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A split central air conditioning system is installed with the control Transformer located in the Attic hung air handler and the condensing unit located outside. The low voltage wire from the thermostat is run to the |
Air handler |
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The typical gauge wire that is used in low voltage control circuits is _______ gauge |
18 |
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A round to rectangular fitting is called a |
Square to round |
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A fitting used to change the size of a square or rectangular duct is called a |
Transition |
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Even though the cooling wire (usually the Y wire) runs from the thermostat to the air handler, it actually just continues on to the condensing unit. Why isn't the cooling wire run directly from the thermostat to the condensing unit? |
To prevent running a third set of wires |
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A split Central cooling system is installed with the control Transformer located in the Attic hung air handler and the condensing unit located outside. How many low voltage conductors need to be run to the condensing unit |
2 |
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What materials can be used successfully in an air conditioning duct system |
Galvanized metal, aluminum, and fiberglass (ductboard) |
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If a duct system has large air leaks at the connections what can be used to seal them up? |
Mastic |
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How much does sunshine affect the operation of a condensing unit |
Very little |
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For what is compressor crankcase heat used |
To prevent liquid refrigerant from accumulating under the oil in the crankcase |
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What is the purpose of insulation on the suction line |
To prevent condensation and maintain superheat |
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What should be done if the voltage to the unit is to low |
Contact the utility company |
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Describe natural draft heating/cooling |
Air being moved by natural air movement |
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List four desired characteristics of a duct system |
1. No air movement will be felt 2. No air noise will be noticed 3. No temperature swings will be felt 4. Occupants will not be aware that the system is on or off unless it stops for a long time and the temperature changes |
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