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Vermont Castings Jefferson Vent Free Gas Heater
4. Compare the maximum BTU/hour rating the space
can support with the total BTU/hour used by the appli-
ances.
Example:
76,800 BTU/hour the space can support
80,000 BTU/hour used by appliances
In this example, the maximum BTU/hour that the space
can support is less than the total used by the appli-
ances. The space is considered to be
Confined Space.
Additional air must be provided to meet the require-
ments of the vent-free heater.
A confined space may be ventilated in two ways:
A. Open or provide at least two ventilating grilles to an
adjoining unconfined space. (Fig. 2)
Each of the two grilles must provide an opening of at
least 50 square inches, with all opening dimensions
being at least 3”. One grille must be within 12” of the
ceiling; the other within 12” of the floor. (If the total
exceeds 100,000 BTU/hour, additional grilles will be
needed.)
B. Vent the room directly to the outdoors. (Provide one
square inch of opening for each 4,000 BTU/hour)
For further information on ventilation guidelines and
sizing specifications, follow the National Fuel Gas
Code/NFPA 54/ANSI Z223.1, Section 5.3.
If the total BTU/hour used by the appliances is less
than the maximum BTU/hr the space can support, the
room meets the
Unconfined Space
criteria and no
further ventilation is needed.
Option 1 -
Vents to
Adjoining
Rooms
Option 3 -
Vents to
Adjoining
Room
Option 2 -
Remove Door to
Adjoining Room
Fig. 5 Supplementing ventilation air.
VO370-2
WARNING
This heater shall not be installed in a confined
space unless provisions are made for adequate
combustion and ventilation air.
WARNING
If the area in which the heater may be operated is
smaller than that defined as an unconfined space,
provide adequate combustion and ventilation air by
one of the methods described in the National Fuel
Gas Code, ANSI Z223.1, 1992 Section 5.3.