Final answer:
The minimum area of each indoor combustion air opening for the boiler is 16.25 square inches and for the hot water heater is 7.5 square inches.
Step-by-step explanation:
The minimum area of each indoor combustion air opening can be calculated using the input ratings of the boiler and hot water heater. To calculate it, we need to know the required free area for 1,000 Btu/h of combustion air. According to the National Fuel Gas Code (NFPA 54), the required free area is 1 square inch for every 4,000 Btu/h of the input rating.
For the 65,000 Btu/h boiler, the required free area would be 65,000 Btu/h divided by 4,000 Btu/h/square inch, which equals 16.25 square inches.
For the 30,000 Btu/h hot water heater, the required free area would be 30,000 Btu/h divided by 4,000 Btu/h/square inch, which equals 7.5 square inches.