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33 Cards in this Set
- Front
- Back
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List the methods of heat transfer |
Conduction, convection, radiation |
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Describe heat energy |
Energy in motion from hot to cold |
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Purpose of a high limit switch on a basic gas fired furnace |
Shuts of MGV when the plenum over heats |
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What are 4 purposes of automatic controls |
Comfort, economy, convenience, safety |
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What is the range of a high limit switch |
89-93 (basic furnace) 82-94 (combination fan control) |
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Typical range setting for a fan OFF switch |
32-38 |
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What is the rating for a high efficiency furnace |
90-98% AFUE (Annual fuel utilization efficiency) |
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In a combination gas valve what does the thermocouple supply |
Power unit |
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Taking a open circuit voltage on a thermocouple should be between? |
26-32mV |
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The main exhaust fan is interlocked with what |
Furnace fan
Keep the interior and exterior pressure the same |
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What is typically the difference between a 24 V and 120 V thermostat |
24 V has an anticipator |
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Is the rollout switch in a high-efficiency furnace a automatic reset or a manual reset |
Manual reset |
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What two auxiliary components associated with mid and high-efficiency furnaces |
Humidifier and electric air cleaner |
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List for types of humidifiers that can be used on furnaces |
Rotating drum Rotating disk Flow-through humidifier Standing water absorbent pad |
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the combustion air blower forces air directly into the |
The flue |
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Heating systems are rated by input values typically using the units |
Btu/h kWatt |
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RTD stands for |
Resistance temperature detection |
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In a basic heating system what devices initiate a change |
Thermostats and fan control |
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Liquid bulb type sensor has few benefits to its design what are they |
Good for liquid temp measurements Ambient temperatures doesn't affect Capillary tubes much |
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Thermeopiles can create up to how many millivolts during operations |
800 mV |
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Solenoid gas valves open do too what kind of force |
Magnetic |
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Diaphragm valves open when what's applied |
Gas pressure |
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Which type of temperature sensing device can with stand 1500° |
Pyrometers |
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Combination gas valves have four main components |
Gas valve Manuel on/off pilot Main gas valve Safety gas valve |
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Taking a close circuit reading of a thermocouple should be? |
7.5-15 mV |
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Last four factors that affect human comfort |
Humidity ,air movement ,radiation and temperature |
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A counter-flow furnace |
Forces got air out the bottom Requires more than one high limit Commonly used in mobile homes |
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What is connected in series with the thermocouple |
Powerpile or thermopile |
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Thermeocouples generates a voltage by a principal called what |
Thermoelectricity |
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What does the fan ON setting come on between |
49-60 |
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What temperature does the fan shut off at |
32-38 |
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What temperature does the blower fan shut off at |
32-38 |
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Humidity n temp in doors |
40% 22 degrees |
