What is the volume of flue gas produced by a 60,000 BTU/h Category I fan assisted natural gas furnace operating with 50% excess air?

To determine the volume of flue gas produced by the 60,000 BTU/h Category I fan-assisted natural gas furnace operating with 50% excess air, we first need to understand the combustion process.

Natural gas has a specific combustion characteristic, typically requiring about 10 cubic feet of air to burn 1 cubic foot of gas completely. Since we want to find the total volume of flue gases produced including the excess air, we must account for both the air used in combustion and the gas itself.

Given that the furnace output is 60,000 BTU/h, we can calculate the volume of gas burned. Natural gas produces about 1,000 BTU per cubic foot when combusted. Therefore, the volume of natural gas consumed is calculated by:

60,000 BTU/h ÷ 1,000 BTU/ft³ = 60 ft³/h of natural gas.

In a standard combustion process with the correct air-to-fuel ratio, we would use 10 cubic feet of air for every cubic foot of gas. However, with 50% excess air, we need to increase the air volume:

For the 60 ft³ of gas burned:

• Required air = 60 ft³ ×