What is the minimum nominal size for a supply line required for two furnaces rated at 135,000 BTU/h each?

To determine the minimum nominal size for a supply line serving two furnaces rated at 135,000 BTU/h each, it's crucial to understand the total BTU load and refer to the appropriate gas piping tables.

The total load from the two furnaces is calculated by adding their individual ratings, yielding a total of 270,000 BTU/h. When sizing gas supply lines, it is essential to consider the capacity of the piping in relation to the total BTU demand, as well as factors like the length of the run and the type of gas.

Manufacturers and regulatory codes, including the National Fuel Gas Code, provide tables that outline the capacity of different pipe sizes based on the BTU ratings and the length of the supply line. For a total load of 270,000 BTU/h, the proper pipe size is determined by these guidelines. Typically, a 1-inch nominal pipe is rated to handle this capacity over a standard length.

Using a larger pipe size, such as 1 1/4 inch or 1 1/2 inch, would certainly be acceptable and might be recommended in certain scenarios (e.g., longer distances or specific installation requirements); however, for the question, the nominal size of 1