Backdrafting

Heating · Venting Gas Furnaces · printed page 126 (PDF page 127)

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Venting – Gas Furnaces

Text in the illustration

if there is insufficient air available to the furnace, backdrafting can occur
check for it at the draft hood - with a match, etc., or just check for excess heat in the area
rust may also indicate a backdrafting problem
supply plenum
vent connector
look for rust around the draft hood due to backdrafting
draft hood
cold air return
smoke test
combustion products
gas furnace
air filter

Generated explanation

The illustration depicts a gas furnace with an exposed burner compartment, draft hood, and vent connector rising from the top. Dashed outlines indicate the supply plenum and cold air return, with an air filter at the return opening. A large arrow shows combustion products spilling out of the draft hood into the surrounding space rather than exhausting through the vent connector. A hand holding a smoking match illustrates a draft check at the hood, and a callout identifies rust around the hood as a possible sign of backdrafting. The annotations explain that insufficient air available to the furnace can cause backdrafting and that excess heat near the hood may also indicate the problem.

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