What type of draft system uses fans, located at the top of the furnace, to pull air up through the furnace?
A) Forced draft
B) Natural draft
C) Balanced draft
D) Induced draft
Answer: D
Explanation: A) Incorrect. A forced draft furnace uses fans or blowers located at the base of the furnace to force air into the air registers.
B) Incorrect. A natural draft furnace has no fans or mechanically produced draft.
C) Incorrect. A balanced draft furnace uses two fans to facilitate airflow: one providing positive pressure to the burners (forced draft) and one pulling flow out of the firebox through the stack (induced draft).
D) Correct. An induced draft furnace uses fans, located at the top of the furnace, to pull air up through the furnace.
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