Desa VSGF33NRC - Manual (Page 6)

www.desatech.com 119304-01A 
AIR FOR COMBUSTION
AND VENTILATION
Continued
PROVIDING ADEQUATE
vENTILATION
The following are excerpts from National Fuel
Gas Code, ANSI Z223.1/NFPA 54, Section 5.3,
Air for Combustion and Ventilation.
All spaces in homes fall into one of the three fol-
lowing ventilation classifications:
1. Unusually Tight Construction
2. Unconfined Space
3. Confined Space
The information on pages 5 through 7 will help you
classify your space and provide adequate ventilation.
Unusually Tight Construction
The air that leaks around doors and windows may
provide enough fresh air for combustion and ven-
tilation. However, in buildings of unusually tight
construction, you must provide additional fresh air.
Unusually tight construction is defined as
construction where:
a. walls and ceilings exposed to the out-
side atmosphere have a continuous
water vapor retarder with a rating of one
perm (6 x 10
-11 kg per pa-sec-m 2 ) or less
with openings gasketed or sealed and
b. weather stripping has been added on
openable windows and doors and
c. caulking or sealants are applied to
areas such as joints around window
and door frames, between sole plates
and floors, between wall-ceiling joints,
between wall panels, at penetrations for
plumbing, electrical, and gas lines, and
at other openings.
If your home meets all of the three criteria
above, you must provide additional fresh air.
See Ventilation Air From Outdoors, page 7.
If your home does not meet all of the three
criteria above, proceed to Determining
Fresh-Air Flow For Heater Location.
Confined and Unconfined Space
The National Fuel Gas Code, ANSI Z223.1/
NFPA 54 defines a confined 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 aggregate input
rating of all appliances installed in that space and
an unconfined space as a space whose volume is
not less than 50 cubic feet per 1,000 Btu per hour
(4.8 m 3 per kw) of the aggregate input rating of
all appliances installed in that space. Rooms com-
municating directly with the space in which the
appliances are installed*, through openings not
furnished with doors, are considered a part of the
unconfined space.
* Adjoining rooms are communicating only if
there are doorless passageways or ventilation grills
between them.
DETERMINING FRESH-AIR FLOW
FOR FIREPLACE LOCATION
Determining if You Have a Confined or
Unconfined Space
Use this work sheet to determine if you have a
confined or unconfined space.
Space: Includes the room in which you will install
fireplace plus any adjoining rooms with doorless pas-
sageways 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.
(volume of space)
Example: Space size 20 ft. (length) x 16 ft.
(width) x 8 ft. (ceiling height) = 2,560 cu. ft.
(volume of space)
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. Multiply the space volume by 20 to determine
the maximum Btu/Hr the space can support.
__________ (volume of space) x 20 = (Maxi-
mum Btu/Hr the space can support)
Example: 2,560 cu. ft. (volume of space) x 20 =
51,200 (maximum Btu/Hr the space can support)
3. Add the Btu/Hr of all fuel burning appliances in
the space.
Vent-free fireplace __________ Btu/Hr
Gas water heater* __________ Btu/Hr
Gas furnace __________ Btu/Hr
Vented gas heater __________ Btu/Hr
Gas fireplace logs __________ Btu/Hr
Other gas appliances* + ________ Btu/Hr
Total = ________ Btu/Hr
* Do not include direct-vent gas appliances. Di-
rect-vent draws combustion air from the outdoors
and vents to the outdoors.
While it is good to make your home energy effi-
cient, your home needs to breathe. Fresh air must
enter your home. All fuel-burning appliances need
fresh air for proper combustion and ventilation.
Exhaust fans, fireplaces, clothes dryers, and fuel
burning appliances draw air from the house to
operate. You must provide adequate fresh air for
these appliances. This will insure proper venting
of vented fuel-burning appliances.