All installations and services must be performed by qualified service personnel.
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Recommended materials for the combustion air duct are smooth, round, galvanized
steel duct or schedule 20 PVC pipe. The maximum intake duct length allowed is
equivalent to 40-feet of straight duct. Reduce this length by 6-feet for the intake hood
and each 90-degree elbow used, and by 3-feet for each 45-degree elbow used the
combustion air duct.
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CAUTION:
Flexible, spiral, or corrugated duct is not
recommended, due to the relatively high-pressure drop associated with air movement
through this type of passageway.
Optional combustion air- a 4” round duct may be used by connecting a 3 x 4 reducer to
the 3” flex duct supplied with the furnace.
Figure 6
