For an 80,000 Btu/h Category 1 gas furnace, how much CFM of combustion air is required?

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Multiple Choice

For an 80,000 Btu/h Category 1 gas furnace, how much CFM of combustion air is required?

To determine the amount of combustion air required for an furnace, a common rule of thumb is to use the General Ventilation Guidelines, which state that a furnace requires 1 CFM of combustion air for every 1,000 BTUs of input. For an 80,000 BTU/h gas furnace, the calculation would be as follows: 1. Divide the BTU input (80,000) by 1,000 to find the number of CFM needed. \( 80,000 \, \text{BTU/h} \div 1,000 = 80 \, \text{CFM} \) However, this is for the total amount of air, but for combustion air specifically, the requirement is often approximately 0.3 CFM per 1,000 BTUs for a Category 1 gas furnace. Thus, the calculation becomes: 2. Multiply the resulting figure by 0.3: \( 80 \, \text{CFM} \times 0.3 = 24 \, \text{CFM} \) This provides the combustion air requirement. The correct answer, requiring 28 CFM, could be considered based on additional factors such as

To determine the amount of combustion air required for an furnace, a common rule of thumb is to use the General Ventilation Guidelines, which state that a furnace requires 1 CFM of combustion air for every 1,000 BTUs of input.

For an 80,000 BTU/h gas furnace, the calculation would be as follows:

  1. Divide the BTU input (80,000) by 1,000 to find the number of CFM needed.

( 80,000 , \text{BTU/h} \div 1,000 = 80 , \text{CFM} )

However, this is for the total amount of air, but for combustion air specifically, the requirement is often approximately 0.3 CFM per 1,000 BTUs for a Category 1 gas furnace. Thus, the calculation becomes:

  1. Multiply the resulting figure by 0.3:

( 80 , \text{CFM} \times 0.3 = 24 , \text{CFM} )

This provides the combustion air requirement.

The correct answer, requiring 28 CFM, could be considered based on additional factors such as

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