What is the draft reading from the over-fire draft test on an oil burner?

What is the draft reading from the over-fire draft test on an oil burner?

• A. -0.02 WC
• B. 0.02 WC
• C. -0.20 WC
• D. 0.20 WC

Answer: (A)

The over-fire draft test checks the slight suction in the flue when the burner is running, measured in inches of water column. For a properly operating oil burner, you want a small negative pressure—just enough to pull the combustion gases up the stack without starving the flame. A reading of -0.02 in wc fits that typical range and indicates the draft is enough to vent correctly without being too strong. A positive reading, like 0.02 in wc, would mean the flue is slightly pressurized, which can push exhaust back toward the burner and disrupt combustion. Readings with a larger magnitude, such as -0.20 or 0.20 in wc, show excessive draft or resistance in the venting path and are not acceptable for normal operation.

The over-fire draft test checks the slight suction in the flue when the burner is running, measured in inches of water column. For a properly operating oil burner, you want a small negative pressure—just enough to pull the combustion gases up the stack without starving the flame. A reading of -0.02 in wc fits that typical range and indicates the draft is enough to vent correctly without being too strong. A positive reading, like 0.02 in wc, would mean the flue is slightly pressurized, which can push exhaust back toward the burner and disrupt combustion. Readings with a larger magnitude, such as -0.20 or 0.20 in wc, show excessive draft or resistance in the venting path and are not acceptable for normal operation.