Which option lists the fuel quantity for a 250 MBH appliance in the example?

Which option lists the fuel quantity for a 250 MBH appliance in the example?

• A. 100 cf of c3h8
• B. 250 cf of ch4
• C. 2500 cf T.A.
• D. 3360 cf T.C.A

Answer: (D)

For a gas-fired appliance, the quantity shown for sizing is often given as the volume of air needed to support the burn, not just the gas volume. In the example, the 250 MBH input is paired with the total combustion air (T.C.A.) required, so the fuel quantity is expressed as 3360 cubic feet per hour of air. This reflects the amount of air necessary to achieve complete combustion for that heat input, incorporating the air-to-fuel ratio used in the calculation and any safety or efficiency factors the example uses. To put it in context, 250 MBH means 250,000 BTU per hour. The gas volume needed is only a few hundred cubic feet per hour, but the corresponding air required to burn that fuel at proper stoichiometry ends up in the thousands of cubic feet per hour. The 3360 cf T.C.A. aligns with the example’s convention of listing fuel requirements as total combustion air, hence it’s the correct choice. The other options either mix in incorrect fuels, wrong units, or mislabel the quantity that the example defines as the fuel (air) quantity.

For a gas-fired appliance, the quantity shown for sizing is often given as the volume of air needed to support the burn, not just the gas volume. In the example, the 250 MBH input is paired with the total combustion air (T.C.A.) required, so the fuel quantity is expressed as 3360 cubic feet per hour of air. This reflects the amount of air necessary to achieve complete combustion for that heat input, incorporating the air-to-fuel ratio used in the calculation and any safety or efficiency factors the example uses.

To put it in context, 250 MBH means 250,000 BTU per hour. The gas volume needed is only a few hundred cubic feet per hour, but the corresponding air required to burn that fuel at proper stoichiometry ends up in the thousands of cubic feet per hour. The 3360 cf T.C.A. aligns with the example’s convention of listing fuel requirements as total combustion air, hence it’s the correct choice. The other options either mix in incorrect fuels, wrong units, or mislabel the quantity that the example defines as the fuel (air) quantity.