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Radiance Vent-Free Gas Heater
2. Divide the volume of space by 50 cubic feet. The re-
sult 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 appliances
installed in the same space, including the following:
Gas Water Heater
Gas Fireplace Logs
Vented Gas Heater*
* Do not include Direct Vent appliances as these utilize
outside air for combustion and vent to the outdoors.
Gas Range
Unvented Heater +33,000 Btu/hr
Total
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 appliances,
the space is considered to be Confined space. Addi-
tional air must be provided to meet the requirements 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.
Fig. 4 Vent options to provide additional air.
8
Gas Furnace
Unvented Gas Heater
Other Gas Appliances*
Example:
55,000 Btu/hr
88,000 Btu/hr
Option 1
Vents to
Adjoining
Room
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 fur-
ther 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.
W A R N I N G
This heater shall not be installed in a confined
space unless provisions are made for adequate
combustion and ventilation air.
W A R N I N G
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.
Option 3 -
Vents to
Adjoining
Room
Option 2
- Remove
Door to
Adjoining
Rooms
vent370-2
Ventilation options
3/26/99 djt
12"
12"
VO370-2
20004555
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