Determine that there is no blockage or restriction, be designed so that the return air to the furnace is not less than 500F (1 OOC) during heating operation. Gas piping must not be run in or through air ducts, chimneys, gas vents, elevator shafts,
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Completely seal supply and return air ducts to furnace casing. Duct system must run to an area outside furnace room or closet. Seal duct work wherever it exchanger blockage and damage to heat exchanger . Select a location that meets all requirements described in this manual for the