Owner`s manual

27407-4-1010 Page 13
The space in the above example is a conned space because the
actual BTU/Hr used is more than the maximum BTU/HR the space
can support. You must provide additional fresh air. Your options
are as follows:
A. Rework worksheet, adding the space of an adjoining room. If
the extra space provides an unconned space, remove door
to adjoining room or add ventilation grills between rooms. See
Ventilation Air From Inside Building.
B. Vent room directly to the outdoors. See Ventilation Air From
Outdoors.
C. Install a lower BTU/Hr heater, if lower BTU/Hr size makes room
unconned.
If the actual BTU/Hr used is less than the maximum BTU/Hr the
space can support, the space is an unconned space. You will need
no additional fresh air ventilation.
WARNING

space.
Ventilation Air
Ventilation Air From Inside Building (Figure 6)
This fresh air would come from an adjoining unconned space. When
ventilating to an adjoining unconned space, you must provide two
permanent openings: one within 12" of the ceiling and one within
12" of the oor on the wall connecting the two spaces (see options
1 and 2, Figure 5). You can also remove door into adjoining room
(see option 3, Figure 5). Each ventilation grill or opening shall have
a minimum free area of one square inch per 1,000 BTUH of the total
input rating of the gas equipment in the conned space.
Figure 6
WARNING
Rework worksheet, adding the space of the adjoining

fresh air to supply all appliances in both spaces.
Ventilation Air From Outdoors (Figure 6)
Provide extra fresh air by using ventilation grills or ducts. You must
provide two permanent openings: one within 12" of the ceiling and
one with 12" of the oor. Connect these items directly to the outdoors
or spaces open to the outdoors. These spaces include attics and
crawl spaces. In most cases for direct communication with the
outdoors or direct communication through a vertical duct a free
area opening of one square inch per 4,000 BTU/Hr of heater input
rating for each grill. If a horizontal duct is used, a grill free area or
duct opening shall have a free area opening of one square inch per
2,000 BTU/Hr for each grill. Follow the National Fuel Code ANSI
Z223.1/NFPA54, Air for Combustion and Ventilation for required
size of ventilation grills or ducts.
IMPORTANT: Do not provide openings for inlet or outlet air into attic
if attic has a thermostat-controlled power vent. Heated air entering
the attic will activate the power vent.
Figure 7
PROVISIONS FOR ADEQUATE COMBUSTION & VENTILATION AIR (continued)