Provisions For Adequate Combustion And Ventilation Air - Williams 0656542.9 Owner's Manual

Provisions for Adequate Combustion and
Ventilation Air
Supplying Adequate Ventilation
The following information will help you provide adequate
ventilation.
Unusually tight construction is defined as construction where:
a. walls and ceilings exposed to the outside atmosphere
have a continuous water vapor retarder with a rating
of one perm (6 x 10
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.
WARNING: If the area in which the heater may
be operated is of unusually tight construction,
provide adequate combustion and ventilation air
by one of the methods described in the National
Fuel Gas Code, ANSIZ223.1, Section 5.3 or
applicable local codes.
Determining If You Need Additional Fresh Air.
Space: Includes the room in which you will install heater 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. (volume
of space)
Example: Space size 22 ft. (length) x 18 ft. (width) x 8 ft.
(ceiling height) = 3,168 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. Divide the space volume by 50 cubic feet to determine the
maximum Btu/hr the space can support, (volume of space)
divided by 50 cu. ft. = (Maximum Btu/hr the space can
support.
Example: 3,168 cu. ft. (volume of space) divided by 50
cu. ft. = 63.36 or 63,360 (maximum Btu/hr the space can
support)
3. Add the Btu/hr of all fuel burning appliances in the space.
Gas water heater* _____________Btu/hr
Gas heater
Vented gas heater ______________Btu/hr
Gas fireplace logs __________Btu/hr
Other gas appliances* +__________Btu/hr
Total
Example: Gas Heater
Vent-free heater
Total
-11 2
kg per pa-sec-m ) or less with
_______________Btu/hr
=_____________Btu/hr
30,000 Btu/hr
+39,000 Btu/hr
=69,000Btu/hr
*Do not include direct-vent gas appliances. Direct-vent
draws combustion air from the outdoors and vents to the
outdoors.
4. Compare the maximum Btu/hr the space can support with
the actual amount of Btu/hr used.
__________Btu/hr (maximum the space can suppot)
__________Btu/hr (actual amount of Btu/hr used)
Example: 63,360 Btu/hr (maximum the space can suppot)
69,000 Btu/hr (actual amount of Btu/hr used)
If 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 necessary air,
remove door to adjoining room or add ventilation grills
between rooms. See Ventilation Air From Inside
Building.
B. Install a lower Btu/hr heater, if lower Btu/hr size
makes room unconfined.
If the actual Btu/hr used is less than the maximum Btu/hr
the space can support, you will need no additional fresh air
ventilation.
Ventilation Air from Inside Building
This fresh air would come from an adjoining room. When
ventilating to an adjoining room, 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.
You can also remove door into adjoining room.
Ventilation Air from Outdoors
Provide extra fresh air by using ventilation grills or ducts. You
must provide two permanent openings: one within 12" of the
ceiling and one within 12" of the floor. Connect these items
directly to the outdoors or spaces open to the outdoors. These
spaces include attics and crawl spaces. Follow the National
Fuel Gas Code NFPA 541 ANSI 2223. 1, Section 5.3, 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.
In Canada:
When combustion air supply is for the unvented room heater
only, it shall be sized at the rate of one (1) square inch per
1000 Btu/hr (.29KW) from outdoors. However, combustion air
is acceptable when available from the principal heat source
and sized to the current CAN/CGA B149.1 or .2 requirements.
Where unvented equipment is installed in an area separated
from a combustion air supply by a door, then permanent
openings, grilles or louvers shall be provided. One shall be
within 18 inches (46 cm) from the ceiling, and one 18 inches
(46 cm) from the floor, sized to one (1) square inch per 1000
Btu (0.29 KW) to allow free movement of air with the source of
combustion air supply.
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