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Installation instructions and Owner’s Manual
1. Find the volume of the space by multiplying room
length x width x height.
Example: Space size 18ft (length) x 18ft. (width) x 8ft.
(height) = 2592
If additional ventilation to adjoining room is supplied with
grills or openings, add the volume of these rooms to the
total volume of the space.
2. Divide the space volume by 50 cubic feet to deter-
mine the maximum Btu/hr the space can support.
Example: 2592 cu.ft. (volume of space) / 50 cu.ft. = 51.8
or 51,800 (maximum Btu/hr the space can
support)
WARNING:
If the area in which the heater may be
operated is smaller than defined as an unconfined
space or if the building is of unusually tight construc-
tion, provide adequate combustion and ventilation air
by the methods described in the
National Fuel Gas
Code, NFPA 54/ ANSI Z223.1,
Section 5.3 or
applicable local codes.
3. Add the Btu/hr of all the fuel-burning appliances in the
space such as, Vent–free heater, Gas water heater,
Gas furnace, Vented gas heater, Gas fireplace logs,
and Other gas appliances*
*Do not include direct-vent gas appliances. Direct-
vent draws combustion air from the outdoors and
vents to the outdoors.
Example:
Gas water heater
40,000 Btu/hr
Vent Free 20,000 Btu/hr
Total
=60,000 Btu/hr
4. Compare the maximum Btu/hr the space can support
with the actual amount of Btu/hr used.
Example:
51,800 Btu/hr (maximum Btu/hr the
space can support)
60,000 Btu/hr (Actual amount of Btu/hr
used)
The space in the above example is a confined 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, and the space of an adjoining
room. If the extra space provides an unconfined
space, remove door to adjoining room or add ventila-
tion grills between the rooms. See Ventilation Air
From Inside Building (Fig. 2)
B. Vent room directly to the outdoors. See Ventilation Air
From Outdoors (Fig. 3).
C. Install a lower Btu/hr heater if lower Btu/hr size makes
room unconfined.
If actual Btu/hr used is less than the maximum Btu/
hr the space can support, the space is an uncon-
fined space. You will need no additional fresh air
ventilation.
VENTILATION AIR
Ventilation from Inside Building
This fresh air would come from an adjoining unconfined
space. When ventilation to an adjoining unconfined
space, you must provide two permanent openings: one
within 12” of the ceiling and one within 12” of the floor on
the wall connecting the two spaces (see options 1 & 2 of
fig. 2). You can also remove door into adjoining room
(see option3, fig 2). Follow the National Fuel Gas Code
NFPA 54/ ANSI Z223.1, Section 5.3, Air for Combustion
and Ventilation for required size of ventilation grills or
ducts.
Figure 2
WARNING:
Rework worksheet, adding the space of
the adjoining unconfined space. The combined space
must have enough fresh air to supply all appliance in
both spaces.
Figure 3.
Ventilation from Outdoors
If necessary provide extra fresh air by using ventilation
grills or ducts. Connect these items directly to the
outdoors or spaces open to the outdoors. These include
attics* and crawl spaces. Follow the National Fuel Gas
Ventilation
Gills into
Adjoining
Room -
Option 1
Ventilation Gills into
Adjoining Room -
Option 2
12”
12”
Or remove
door into
Adjoining
Room -
Option 3
INLET
AIR
OUTLET
AIR
VENTILATION CRAWL SPACE
TO CRAWL
SPACE
TO ATTIC
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VENTILATION AIR
VENTILATED
ATTIC
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OUTLET AIR
