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Vermont Castings Radiance Vent-Free Gas Heater
20004555
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.
with a volume of 1152 cubic feet. The total space
volume is 3840 cubic feet. (1728 + 960 + 1152).
2. Divide the volume of space by 50 cubic feet. The
result is the maximum BTU/Hr that the space can
support.
Example:
3840 divided by 50 = 76.8 or 76,800 BTU/Hr.
3. Add the BTU/Hr ratings of all fuel-burning appli-
ances installed in the same space, including the
following:
Gas Water Heater Gas Furnace
Gas Fireplace Logs Unvented Gas Heater
Vented Gas Heater* Other Gas Appliances*
* Do not include Direct Vent appliances as these
utilize outside air for combustion and vent to the
outdoors.
Example:
Gas Range 55,000 BTU/Hr
Unvented Heater +33,000 BTU/Hr
Total 88,000 BTU/Hr
4. Compare the maximum BTU/Hr rating the space can
support with the total BTU/Hr used by the appliances.
Example:
76,800 BTU/Hr - max. the space can support
88,000 BTU/Hr - total used by appliances
In this example, the maximum BTU/Hr 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 Unvented heater.
A confined space may be ventilated in two ways:
A) Open up or provide at least two ventilating grilles to
an adjoining unconfined space. Use any of the options
illustrated in Figure 4.
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 located within 12"
of the ceiling; the other within 12" of the floor. (If the
total exceeds 100,000 BTU/Hr, additional grilles will be
required.)
B) Vent the room directly to the outdoors. (Provide one
square inch of opening for each 4,000 BTU/hr.
If the total BTU/Hr used by the appliances is less than
the maximum BTU/Hr the space is able to support, the
room meets the Unconfined space
criteria and no
further ventilation is required.
For further information on ventilation guidelines and
sizing specifications follow the National Fuel Gas Code
NFPA 54/ANSI Z223.1 Section 5.3.
12”
12”
Option 3 -
Vents to
Adjoining
Room
Option 1
Vents to
Adjoining
Room
Option 2 -
Remove
Door to
Adjoining
Rooms
VO370-2
Fig. 4 Vent options to provide additional air.