True or False: For a fuel oil burner installed in an enclosure rated at 1.25 GPH, 175 square inches is the free area needed for each of the two required combustion air openings.

True or False: For a fuel oil burner installed in an enclosure rated at 1.25 GPH, 175 square inches is the free area needed for each of the two required combustion air openings.

• A. False
• B. True
• C. Not stated
• D. Depends on enclosure

Answer: (B)

The test is checking how to size combustion air openings for an oil burner in an enclosure. For oil burners, the required free area of each opening is based on the appliance’s input rating, using a common rule: each opening must provide 1 square inch of free area for every 1,000 Btu per hour of input, and there are two openings. To apply this, convert the fuel input to Btu per hour. An oil burner rated at 1.25 gallons per hour uses about 140,000 Btu per gallon, so the input is roughly 1.25 × 140,000 ≈ 175,000 Btu/h. Dividing by 1,000 gives 175 in^2 of free area required for each opening. Therefore, stating that 175 square inches is the free area needed for each of the two required combustion air openings is correct.

The test is checking how to size combustion air openings for an oil burner in an enclosure. For oil burners, the required free area of each opening is based on the appliance’s input rating, using a common rule: each opening must provide 1 square inch of free area for every 1,000 Btu per hour of input, and there are two openings.

To apply this, convert the fuel input to Btu per hour. An oil burner rated at 1.25 gallons per hour uses about 140,000 Btu per gallon, so the input is roughly 1.25 × 140,000 ≈ 175,000 Btu/h. Dividing by 1,000 gives 175 in^2 of free area required for each opening.

Therefore, stating that 175 square inches is the free area needed for each of the two required combustion air openings is correct.