Crown Boiler CLBR68-112 - Manual (Page 6)

Figure 1: Recommended Support Frame for Horizontal / Counterflow Furnaces
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Closet and Alcove Installation
All furnace models may be installed in a closet or alcove on combustible flooring with
specified (standard) clearances to combustible construction. The horizontal /
counterflow furnace model requires an optional combustible surface-mounting
base (model # CSFB-HC68) for vertical installation (i.e., counterflow
configuration) directly on combustible materials, refer to Figure 2.
Figure 2: Counterflow Furnace Combustible Surface-Mounting Base
Standard Clearances
Standard clearances are mandatory minimum clearances from heated surfaces of the
furnace to combustible materials to assure protection from fire hazard during furnace
operation. (Refer to the Standard for the Installation of Oil-Burning Equipment, NFPA
31-2001, for definitions of combustible and non-combustible materials.)