A sizing table (natural gas) shows 1/2-inch pipe carries 92 cfh and 3/4-inch pipe carries 190 cfh at the governing length. A section supplies a 40,000 BTU/hr wall furnace plus a 45,000 BTU/hr water heater. What is the smallest size that works?

Giải thích

Add the inputs: 40,000 plus 45,000 equals 85,000 BTU/hr, which is 85 cfh of natural gas. The 1/2-inch pipe carries 92 cfh, which is more than 85, so it is adequate at that length. The smallest listed size that meets the 85 cfh demand is 1/2-inch.