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73 Cards in this Set
- Front
- Back
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Tubeaxial fans have what kind of air? |
Turbulent |
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1” of 16g strap is equivalent to... |
3/8” ready rod |
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What does an anemometer measure? |
Air flow |
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What is sensible heat? |
Heat we feel (sense). Measured by a dry bulb thermometer. |
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HVAC means... |
Heating Ventilation Air Conditioning |
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Air conditioning means cooling the air. |
False (changing the properties of the air) |
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What filter is often used as the first stage pre-filters? |
Pleated |
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What filter is used as second stage filters? |
Extended surface |
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What filter removes odors and gases from the air? |
Carbon |
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What does HEPA stand for? |
High efficiency particulate air |
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Humidifying removes moisture from the air? |
False (Adds it) |
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What does an anemometer measure? |
Air flow |
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What does a manometer measure? |
Air pressure |
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What does a sling psychrometer measure? |
Relative humidity |
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What is air ordinarily composed of? |
78% nitrogen, 21% oxygen, 1% miscellaneous gases |
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What is standard air defined as? |
Dry air at 70 degrees and a barometric pressure of 29.92” HG mercury at sea level. |
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Does heated air weigh more or less than cooler air? |
Less. 100 cubic feet of standard air @ 70 degrees weighs 7.5 lbs, but the same volume @ 100 degrees weighs 7.1 lbs |
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What is the point where a sample of air is at 100% relative humidity called? |
Dew point or saturation point. |
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What is radiant heat? |
Hear travelling in straight lines. (Example - campfire) |
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What is convection heat? |
Heat carried on currents of warm air. (Example - upwind of a campfire) |
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What is conduction? |
Heat conveyed through a material. (Example - handle of a frying pan in a fire) |
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What is sensible heat? |
Heat we feel (sense). Measured by a dry bulb thermometer. |
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What is latent heat? |
Heat released or absorbed by a change of state. |
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Where would you find propeller fans? |
Parkades or farm buildings. |
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Tubeaxial fans have... |
Turbulent air |
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Vaneaxial fans produce... |
Straight air flow |
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Squirrel cage, straight blade & backward inclined blade are types of what kind of fan? |
Centrifugal |
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What are examples of outlets? |
Grilles, registers and diffusers. (These are also known as terminal devices) |
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VAV boxes and mixing boxes are examples of what? |
Terminal devices. |
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What is a diffuser and what does it do? |
It’s a supply outlet that slices the air into separate streams |
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What is free area? |
The area of a terminal device through which air can pass. Also known as K factor. |
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12000 BTU is equivalent... |
1 tonne furnace |
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Q = V x A |
Q = CFM V = Velocity (FPM) A = Cross sectional area (sq” or sq’) |
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VP = TP + SP |
Velocity pressure Total pressure Static pressure |
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VP = (V/4005)squared |
To find velocity pressure |
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Velocity pressure is measured with... |
Both straight up and hooked pidot tubes |
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Total pressure is measured with... |
Hooked pidot tube only |
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Static pressure is measured with... |
Straight up pidot tube only. |
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Laminar flow is... |
Air that flows in layers and in a straight line. |
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Turbulent air means... |
The air tumbles and swirls as it moves down the duct. |
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Dynamic loss is due to... |
Pressure loss due to turbulence in the airflow |
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K factor is... |
Free area which is used in grill selection. |
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What does a “low boy” furnace look like? |
Short & fat unit. Return & Supply air on top. |
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What does a counter flow or down flow furnace look like? |
Tall and skinny. Return air & supply air on opposite ends. |
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What does a high boy furnace look like? |
Tall and skinny with supply air on top and return air at the bottom side. |
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What is R value of materials? |
Heat resistance factor. |
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How do you decide furnace size? |
Heat loss calculations. |
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What is the most common duct run? |
Extended plenum |
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Where would you find perimeter duct? |
Rancher on a slab. |
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Where should a thermostat be placed? |
5’ high |
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When doing a 3 gore square to round elbow, which gore is triangulated? |
The middle one, the other two are parallel line development. |
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What measures pressure drop across a coil? |
Manometer |
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What is used to measure air flow volume within a duct? |
Manometer |
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What holds more water? Cold air? Hot air? Humid air? |
Hot air. |
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What fan moves high volumes of air against low static pressure? |
Propeller type fans. |
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Which Exhaust system would you use when tight on space working with medium static pressures? |
Tube-axial |
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A VAV box with a mixing box is used in? |
Dual duct systems. |
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What type of HVAC system draws air evenly across the coils and adds fan heat to supply air? |
Draw through |
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Why do flue gases rise up through venting? |
Because hot gases from combustion are lighter than combustion air. |
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Rooftop installation of fans or package units require... |
Being secured by mechanical fasteners. |
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Which type of vents are made from single walled galvanized steel. |
“C” vents |
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Mixing plenums have outside & return air volumes modulated by what? |
Parallel blade dampers. |
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What is filter efficiency directly related to? |
The type of particulate it was designed for. |
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Which is not a type of control system in VAV boxes? DDC Pneumatic Electric Rheostat |
Rheostat |
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What is not a way to handle indoor air pollution? Diluton Exhaustion Relief |
Relief |
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What can dirty or improperly installed filters create? |
Pressure drops |
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In a refrigeration system what does high pressure created by the compressor do? |
Raises the refrigerant temperature. |
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What should be done to radius duct elbows so they have a lower pressure drop? Put in Turning vanes Make into a square fitting Put in Splitter vanes |
Put in splitter vanes |
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Woth refiners & grilles, what does AK or K factor refer to? |
Free area |
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What prevents vibration from travelling from AHU’s to ductwork? |
Flexible connectors |
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Furnace filters should be placed... |
At the side of the fan cabinet |
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What damper provides the most effective balancing? |
Opposed blade damper |
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Fire dampers are expected to release ______ degrees above normal air temperature. |
50 |
