Gas Fitter Practice Test

What is the required lower opening size for a 60,000 Btuh water heater installed indoors with no draft diverter?

1. An 11 square inch lower opening only

2. An 11 square inch lower opening and an 11 square inch upper opening

3. A 60 square inch lower opening only

4. A 60 square inch lower opening and a 60 square inch upper opening

The correct answer is: A 60 square inch lower opening only

The correct choice states that a 60 square inch lower opening is required. This requirement is based on the BTU rating of the water heater and the need to ensure adequate airflow for combustion. A water heater that operates at 60,000 BTUh requires sufficient air for safe and efficient operation, especially when it does not have a draft diverter. The primary function of the lower opening is to provide the necessary combustion air from the room in which the heater is located. The size of the opening is directly related to the appliance's fuel consumption. By providing a larger lower opening, you ensure that there is enough fresh air available to support complete combustion and prevent the buildup of harmful gases. In contrast, the other options that suggest either an 11 square inch opening or both upper and lower openings also being of 11 square inches, or suggest 60 square inch openings on both areas, do not meet the standards required for a water heater of this size without a draft diverter. For safe appliance operation, a properly sized lower opening is critical to prevent issues such as backdrafting or insufficient combustion air, which can lead to inefficiencies and safety hazards.