What is the required size of the air supply opening for a 1,500,000 Btu/h appliance?

What is the required size of the air supply opening for a 1,500,000 Btu/h appliance?

• A. 300 sq in.
• B. 150 sq in.
• C. 600 sq in.
• D. 900 sq in.

Answer: (A)

The required air supply opening size is based on the appliance’s input rating, using a rule of one square inch of free opening for every 5,000 Btu/h of appliance input. This ensures there’s enough combustion air to support safe, complete combustion and to prevent negative pressure from drawing combustion products back into the space. For a 1,500,000 Btu/h appliance: 1,500,000 ÷ 5,000 = 300 square inches of total air supply opening. So 300 sq in provides the minimum required free-area opening. The other options would not meet this 1 in2 per 5,000 Btu/h rule.

The required air supply opening size is based on the appliance’s input rating, using a rule of one square inch of free opening for every 5,000 Btu/h of appliance input. This ensures there’s enough combustion air to support safe, complete combustion and to prevent negative pressure from drawing combustion products back into the space.

For a 1,500,000 Btu/h appliance: 1,500,000 ÷ 5,000 = 300 square inches of total air supply opening.

So 300 sq in provides the minimum required free-area opening. The other options would not meet this 1 in2 per 5,000 Btu/h rule.