How many square inches are required for combustion air openings for a 1,000,000 BTU boiler with six 80,000 BTU DHW systems?

To determine the amount of square inches required for combustion air openings for a boiler and domestic hot water (DHW) systems, it's important to understand the BTU (British Thermal Unit) requirements and the regulations that dictate ventilation needs.

In this scenario, you have a 1,000,000 BTU boiler and six domestic hot water systems, each requiring 80,000 BTU. The total BTU requirement can be calculated as follows:

1. Total BTU for DHW systems:

6 systems x 80,000 BTU = 480,000 BTU.

2. Total BTU requirement:

1,000,000 BTU (boiler) + 480,000 BTU (DHW) = 1,480,000 BTU.

According to the National Fuel Gas Code and similar standards, the required combustion air openings can be calculated based on the input BTU rating of the equipment. A general guideline is that for each 1,000 BTU/h, approximately 1 square inch of combustion air opening is needed.

Applying this guideline to the total BTU requirement:

1,480,000 BTU / 1,000 BTU/sq inch