Standard Clearances; Air For Combustion And Ventilation - Thermo Products Spirit Series Installation, Operation And Service Manual

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-
2020, or latest edition, for definitions of combustible and non-combustible materials.
Accessibility clearances, which are typically greater, may exceed fire protection
clearances. Therefore, consider providing at least 24 inches of clearance from the front of
the furnace to obstructions and surfaces for adequate service and maintenance access.
The minimum clearances from furnace casing surfaces to combustible materials are:
 0 inches from casing sides and rear
 6 inches from front casing of furnace
 7 inches from flue pipe/vent connector
 1 inches from casing top
 1 inches from any side of supply air plenum
 3 inches above supply air ducts, within 6 feet of furnace

Air for Combustion and Ventilation

c CAUTION: Relief openings in the front or top of the furnace casing should not
be obstructed or blocked. These openings supply combustion and ventilation air
to the furnace.
Chloride, fluoride, iodide, and bromide bearing compounds when present, even in low
concentrations, are in air supplied for combustion to the furnace, can result in accelerated
and severe corrosion of the heat exchanger and/or the venting system.
Often, household chemicals contain chloride-bearing compounds. There are many
compounds representative of this classification of chemicals. A few common examples
are listed below.
 Cleaning solvents
 Varnish and paint removers
 Bleaches
 Fabric softeners
 Water softener salt
 Tile adhesives
Avoid storing or using these chemicals within close proximity to the furnace. In addition,
avoid storing or using any chemicals, of an unknown and possibly flammable nature, in
close proximity to the furnace.
The furnace shall be installed in a location within the building that permits a satisfactory
supply of air for combustion, ventilation, and proper operation of the venting system.
While all forms of building construction cannot be covered in detail in this manual, this
requirement may usually be met by application of one of the following methods in
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