620.4 Clearance.
FGC § 620.4
Suspended-type unit heaters shall be installed with clearances to combustible materials of not less than 18 inches (457.2 mm) at the sides, 12 inches (304.8 mm) at the bottom and 6 inches (152.4 mm) above the top where the unit heater has an internal draft hood or 1 inch (25.4 mm) above the top of the sloping side of the vertical draft hood. Floor-mounted-type unit heaters shall be installed with clearances to combustible materials at the back and one side only of not less than 6 inches (152.4 mm). Where the flue gases are vented horizontally, the 6-inch (152.4 mm) clearance shall be measured from the draft hood or vent instead of the rear wall of the unit heater. Floor-mounted-type unit heaters shall not be installed on combustible floors unless listed for such installation. Clearances for servicing all unit heaters shall be in accordance with the manufacturer's instructions. Exception: Unit heaters listed for reduced clearance shall be permitted to be installed with such clearances in accordance with their listing and the manufacturer's instructions and as approved by the department.
