DUCTING
PRIMARY FURNACE
To install the GBU070 as a “Primary Furnace” first locate the furnace as near the chimney and as centralized with respect to heat distribution as practical. Follow all clearance to combustible requirements. Connect the ductwork to the furnace. Minimum supply plenum size: 14” x 14”, minimum return plenum size: 12” round. When a furnace is installed so that supply ducts carry air circulated by the furnace to the areas outside the space containing the furnace, the return air must also be handled by a duct sealed to the furnace casing and terminating outside the space containing the furnace. Where there is no complete return duct system, the return connection must be run full size to a point outside the furnace room. Air duct systems should be installed in accordance with standards for air conditioning systems. NFPA Pamphlet #90. They should be sized in accordance with ACCA Manual D or whichever is applicable, after completing installation as per the appropriate section of this manual.
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