What is a good over the fire draft measurement in a natural draft furnace?

• A. 0.01 inches of water
• B. 0.05 inches of water
• C. 0.1 inches of water
• D. 0.15 inches of water

Answer: (B)

A good over the fire draft measurement in a natural draft furnace is typically around 0.05 inches of water. This measurement indicates that there is sufficient draft to ensure that combustion gases are effectively drawn up through the chimney, allowing for efficient operation of the furnace.

Maintaining the right level of over the fire draft is crucial for optimal combustion and emission control. A measurement that is too low could indicate inadequate draft, potentially leading to improper combustion and increased emissions of pollutants. On the other hand, a measurement that is too high can cause excessive heat loss and increase wear on the system components due to higher flow rates of combustion gases.

In this context, the other values either indicate insufficient or excessive draft, making 0.05 inches of water the ideal measurement for good combustion efficiency in a natural draft furnace.