EnviroPro Combustion & Waste Heat Recovery Solutions
Tech Resources

02/Draft Flow Chart
Flow chart for balancing Draft and Excess O2 on Natural Draft Heaters

*Natural Draft Furnaces are typically designed to operate at -.1 “WC at the arch. Refer to heater data sheets to determine how your specific heater was designed.
**Draft High means the draft at the arch more negative than the target. (ie. -.4”WC)
***Draft Low means the draft at the arch less negative than the target. (ie. -.02”WC)
Low or High O2 refers to the O2 content of the flue gas at the arch.
When under low O2 conditions, the above recommendations assume that combustibles and CO remain within acceptable levels.

02 Draft Flowchart
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