4-22. High Draft
High draft pulls gases up the chimney before they are burned and causes a high consumption of fuel oil, a lack of heat, a
fluctuating flame and formation of soot. High draft is caused by additional lengths of stove pipe added to the original
lengths or high winds. High draft is generally controlled by the draft regulator. If necessary, with an extremely high draft,
install another draft regulator above the original one.
4-23. Low Draft
Low draft causes a lazy, smoky flame, formation of soot, and a lack of heat. It is caused by loose fitting pipe and / or
restricted flues or chimneys. Be sure each section of stove pipe fits tightly together, and the flue and chimney passages
are clean and unrestricted.
4-24. Down Draft
a. Down draft is caused by air currents being forced down the stove pipe. It results in fluctuating flame, gas odors
from the heater, and accumulation of soot. Some reasons for down drafts are, the top of the rain cap is below the ridge
of the building; higher buildings on either side or large trees extending above the building.
b. Down drafts may be eliminated by extending the rain cap pipe at least two feet above the roof ridge line. If the
extension is two feet or more, an outer pipe four inches larger in diameter, should be installed around the extension and
sealed at both ends. For higher objects, such as adjoining buildings and high trees. An H type or similar hood will have
to be installed in place of the rain cap.
4-25. Testing for Draft
Hold a lighted match at a narrow opening between the regulator vane and rim. If the flame is drawn into the opening,
there is a draft and the regulator will automatically adjust it to the required .05 inch to .06 inch draft. If the flame is blown
out, there is a down draft. Refer to paragraph 4-24. If the flame burns straight up, there is a low draft. Refer to
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