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46 Cards in this Set
- Front
- Back
What are the three types of combustion |
Perfect Complete Incomplete |
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What are the 4 types of combustion air |
Primary Secondary Excess Dilution |
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Primary air controls |
The amount of fuel that can be burned efficiently |
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Secondary air increases________ ______ by causing the fuel to completely burn |
Combustion efficiency |
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Excess air is air in excess of the air which is theoretically required for combustion. The the burner will improve the mixing of |
The fuel and air |
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If excess air is dramatically increased beyond what is needed the result will be |
Lower flue gas temperatures which lowers combustion efficiency |
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Dilution air does not directly promote the combustion process but is used to control |
The stack effect |
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Combustion efficiency is a calculated measurement of how well the appliance |
converts fuel to usable heat |
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Thermal efficiency is the measurement of the effectiveness of the HEX in |
Removing heat from the fuel burned |
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Annual fuel utilization efficiency (AFUE) is the true measure |
Of an appliance’s efficiency |
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Input-output method is a calculation dividing the |
Output of an appliance by the input and multiplying by 100 |
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Flue gas temperature is the temperature of combustion gases |
As they exit the appliance |
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How much oxygen is in the air |
20% |
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What type of combustion is achieved in a gas burning appliance |
Complete combustion |
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What are the first products produced by incomplete combustion |
Aldehydes |
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Which portion of the air supply is theoretically not required for combustion |
Excess air |
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Which portion of air is used to tune the burner |
Excess air |
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Which efficiency rating accounts for standby losses |
AFUE |
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Which fuel has a higher hydrogen/carbon ratio |
Propane |
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What happens if combustion air temperature is lowered |
Combustion efficiency is lowered |
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Net flue gas is determined by |
Subtracting ambient temperature for the temperature of the gases upstream of the draft control device |
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What happens to the efficiency if the primary air is adjusted |
Little or no difference |
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Why is it important to determine the temperature rise of a forced air furnace |
Ensures the flue gases are transferring the correct amount of heat |
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How do you change the temperature rise of a furnace |
Change the speed of the blower motor |
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What is the typical vent pressure of an atmospheric appliance |
-0.1wc to -0.03wc |
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When conducting flue gas analysis the ultimate amount of carbon dioxide is |
12% |
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Determining the content of oxygen in flue gas allows us to determine the amount of |
Excess air entering the appliance |
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The formula for determining excess air is |
Back (Definition) |
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What is the maximum CO exposure level in 8hr period is |
25ppm |
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When testing vent pressure one opening of the draft gauge connects to the the vent and the other to |
Atmosphere |
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Where should flue gas sample be taken |
In combustion chamber upstream of draft control device |
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What does a very low vent draft indicate |
Appliance is grossly underfired |
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What two readings are required to determine combustion efficiency |
Flue gas temp CO2 content |
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If excess air (O2) is higher than 8% you should |
Reduce the excess air |
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If excess air (O2) reading is below 3.5% you need to |
Add excess air |
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What is a common cause of cracks in heat exchangers |
Metal fatigue |
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What must be done if a defective HEX is found |
Replace the HEX |
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What heat exchangers test requires the use of a butane torch |
Sodium ion test |
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If CO2 decreases, CO |
Increases |
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If AFUE increases, flue gas temperature |
Decreases |
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If too much air is added to the combustion zone, combustion efficiency |
Decreases |
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CO2 level in flue gas should be as |
High as possible |
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Why is it important to determine the amount of unburned oxygen in flue gas |
To see which side of CO2 scale we are on |
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What % of O2 is best in flue gas |
Less than 8% |
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How is net flue gas determined |
Flue gas - ambient air temp |
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Combustion efficiency is found by using |
CO2 and net flue gas temp |