111826-02C
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5
5
40,000
33,000
73,000
AIR FOR COMBUSTION AND
VENTILATION
Continued
WARNING: If the area in which the appliance
may be operated is smaller than that defi ned as an
un con fi ned space or if the building is of unusually
tight construction, provide ad e quate com bus tion and
ven ti la tion air by one of the methods described in
the National Fuel Gas Code, ANSI Z223.1/NFPA 54
Sec tion 5.3 or applicable local codes.
DETERMINING FRESH-AIR FLOW FOR
APPLIANCE LOCATION
Determining if You Have a Confi ned or Unconfi ned
Space
Use this work sheet to determine if you have a confi ned or un con fi ned
space.
Space:
Includes the room in which you will install appliance plus any
adjoining rooms with doorless passageways or ventilation grills between
the rooms.
1. Determine the volume of the space (length x width x height).
Length x Width x Height = ____________cu. ft. (vol ume of space)
Example:
Space size 20 ft. (length) x 16 ft. (width) x 8 ft. (ceil ing
height) = 2560 cu. ft. (vol ume of space)
If additional ventilation to adjoining room is supplied with grills or open-
ings, add the volume of these rooms to the total vol ume of the space.
2. Multiply the space volume by 20 to determine the maximum Btu/Hr
the space can support.
____________(volume of space) x 20 = (Maximum Btu/Hr the space
can sup port)
Example:
2560 cu. ft. (volume of space) x 20 = 51,200 (max i mum
Btu/Hr the space can sup port)
3. Add the Btu/Hr of all fuel burning ap pli anc es in the space.
Vent-free appliance _____________ Btu/Hr
Gas
wa
ter appliance* _____________ Btu/Hr
Gas
fur
nace _____________ Btu/Hr
Vented gas appliance _____________ Btu/Hr
Gas
fi re place logs _____________ Btu/Hr
Other gas appliances* + _____________ Btu/Hr
Total = _____________ Btu/Hr
AIR FOR COMBUSTION AND VENTILATION
Providing Adequate Ventilation (Cont.)
Determining Fresh-Air Flow for Appliance Location
Ventilation Air
Confi ned and Unconfi ned Space
The National Fuel Gas Code, ANSI Z223.1/NFPA 54 defi nes a
con fi ned space as a space whose volume is less than 50 cubic feet
per 1,000 Btu per hour (4.8 m
3
per kw) of the ag gre gate input rating
of all ap pli anc es in stalled in that space and an un con fi ned space as
a space whose vol ume is not less than 50 cubic feet per 1,000 Btu
per hour (4.8 m
3
per kw) of the ag gre gate input rating of all appli-
ances in stalled in that space. Rooms com mu ni cat ing di rect ly with
the space in which the ap pli anc es are in stalled*, through openings
not fur nished with doors, are con sid ered a part of the unconfi ned
space.
* Adjoining rooms are communicating only if there are doorless
passageways or ven ti la tion grills between them.
* Do not include direct-vent gas ap pli anc es. Direct-vent draws com-
bus tion air from the outdoors and vents to the outdoors.
Example:
Gas water appliance _____________ Btu/Hr
Vent-free appliance + _____________ Btu/Hr
Total = _____________ Btu/Hr
4. Compare the maximum Btu/Hr the space can support with the actual
amount of Btu/Hr used.
____________________Btu/Hr (maximum the space can sup port)
____________________Btu/Hr (actual amount of Btu/Hr used)
Example:
51,200 Btu/Hr (max i mum the space can support)
73,000 Btu/Hr (actual amount of Btu/Hr used)
The space in the above example is a con fi ned space because the actual
Btu/Hr used is more than the maximum Btu/Hr the space can sup port. You
must provide additional fresh air. Your op tions are as follows:
A. Rework worksheet, adding the space of an adjoining room. If the ex tra
space provides an unconfi ned space, remove door to ad join ing room or
add ven ti la tion grills between rooms. See Ven ti la tion Air From Inside
Building, page 6.
B. Vent room directly to the outdoors. See Ventilation Air From Out doors,
page 6.
C. Install a lower Btu/Hr appliance, if lower Btu/Hr size makes room un con -
fi ned.
If the actual Btu/Hr used is less than the maximum Btu/Hr the space can sup-
port, the space is an unconfi ned space. You will need no additional fresh air
ven ti la tion.
VENTILATION AIR
Ventilation Air From Inside Building
This fresh air would come from an adjoining unconfi ned space. When
ventilating to an adjoining unconfi ned space, you must pro vide two
permanent open ings: one within 12" of the ceiling and one within
12" of the fl oor on the wall con nect ing the two spaces (see options
1 and 2, Figure 2). You can also remove door into adjoining room
(see op tion 3, Figure 2). Follow the National Fuel Gas Code, ANSI
Z223.1/NFPA 54, Section 5.3, Air for Combustion and Ventilation
for required size of ventilation grills or ducts.
Ventilation Air From Outdoors
Provide extra fresh air by using ventilation grills or ducts. You
must provide two per ma nent open ings: one within 12" of the ceil-
ing and one within 12" of the fl oor. Connect these items directly to
