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41 Cards in this Set
- Front
- Back
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What is a takeoff |
Point of Departure from a duct which a duct fitting is attached to accomplish branching of ductwork |
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What is a grill |
Louvered opening usually found in a return air opening |
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What is a register |
A grill that has a regulated damper device for controlling amount of airflow and vanes to control air Direction |
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What is a plenum |
Abox like fitting in which an air handler discharges or receives air in a duct system |
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What is the equal friction method |
a method of duct design used to measure air flow so the air is distributed proportionately to all conditioned spaces |
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What is system pressure |
The sum of negative and positive static pressure being exerted by a blower |
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What is stratification of air |
Condition in which there is little 15 fpm or no air movement in room, air lies in temperature layers |
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What is the Cascade or waterfall effect |
The transfer of large masses of air due to convection currents in a structure, often caused by warm air rising and cooler air falling through building access such a stairs |
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What is terminal velocity |
An arbitrary maximum velocity of an Airstream which spreads or drops into a living area, usually considered comfortable at 35 to 50 fpm |
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What is primary air |
A mixture of Supply Air from an outlet and room air at velocities above 150 fpm |
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What is floor warming |
Floor heating by burying ducts in concrete slab floors or by running Supply ducts under floors |
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What is free area |
Also known as K-factor, net area of a register or Grille after subtracting area of veins or dampers, typically 70% of gross face area or as specified by manufacturer |
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What are three advantages of perimeter systems |
1 Delivers condition air at points of greatest heat loss and Heat gain which is the outside of the structure 2, allows fewer air returns which are generally located in inner areas of structures 3, delivers the highest level of comfort of any system |
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What are the two disadvantages of a perimeter system |
More costly than many other systems and, may be subject to water problems if ducts are buried under the slab |
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What are six advantages of High inside wall system |
1, Supply Outlets are located Central to main trunk duct so shorter ducts can be used 2, pressure is less so smaller blower may be used 3, doesn't interfere with furniture placement 4, permits longer periods of blower operation 5, well suited for cooling in areas where heating is less important 6, less costly installation |
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What are two disadvantages of high inside Wall systems |
Heating is more difficult because of stratification and, areas of Greater heat loss and gain such as Windows are difficult to condition without special registers |
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What are two advantages of low inside wall system |
Supply Outlets are located close to the blower , and installation is less costly |
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What are five disadvantages of low inside Wall Systems |
Proper air distribution is difficult 2, higher velocities must be avoided 3, furniture placement is difficult 4, difficult to use as a cooling system 5, diffuser veins must be adjusted seasonally |
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What are four advantages of ceiling systems |
1, doesn't interfere with furnace replacement 2, can be located in centre of room or near outside wall 3, well suited for summer Cooling 4, return air can be located on either inside or outside wall near the floor |
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What are the 3 disadvantages of ceiling system |
1, proper selection of Supply registers is critical 2, doesn't heat floors directly 3, can cause room air stratification and large air temperature gradients |
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What five things must be considered when placing return air grilles |
1, return air inlets are not normally placed in a kitchen or bathroom, because of smell and moisture 2, and Optimum system has a return Inlet in each bedroom 3 , return air inlets are normally placed so that air is not dragged over 30 feet from a supply 4, total area of the return air Inlets must carry an air volume equal to or greater than Supply volume 5, return air inlets are usually placed on inside walls which allows shorter ducts |
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What is the air temperature of a forced warm air furnace |
120 degrees Fahrenheit |
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what side of the system is the filter placed on |
always the return air side |
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How are furnaces rated |
In BTUs |
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In what direction does heat travel |
He travels from the high thermal to the low thermal |
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What are the 4 classification of Heating units |
Lowboy, Hi-boy, counterflow, and horizontal |
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Where are lo-boys usually installed |
Usually for basement installations |
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Where are high boy usually installed |
Usually for closet for vestibule installations, can be installed in the basement if clearance is sufficient |
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Where is counter flow usually installed |
For closet or vestibule installations in homes with slab or crawlspace foundations |
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where are horizontal usually installed |
In the Attic or in a crawl space |
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What is the responsibility of the installer |
To ensure that an adequate supply of air is provided for combustion, ventilation, and delusion air if the appliance has a draft Hood |
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What is the preferred method to bring combustion air into a home or building |
To install a combustion air duct which communicates with outside air and ties in directly to the return air duct of a hot-air furnace |
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What is the approximate temperature of the flue gas of a conventional forced air gas furnace |
450° Fahrenheit |
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What is the seasonal efficiency range have a conventional forced air gas furnace |
55 to 65% |
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What are improved conventional furnaces equipped with |
Spark ignition to eliminate a standing pilot light |
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What is the seasonal efficiency range have an improved conventional furnace |
65 to 75% |
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What are the vent gas temperatures on an intermediate efficiency furnace |
300 degrees Fahrenheit |
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What is the seasonal efficiency range of an intermediate efficiency furnace |
80 to 83% |
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What temperature does the high efficiency furnace cool the flue gases down to |
Approximately 100 to 130 degrees Fahrenheit |
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What is a high-efficiency furnace also known as |
A condensing furnace |
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What is the seasonal efficiency of a high-efficiency furnace |
85 to 95% |
