Instructions / Assembly
Installing Your Furnace
AIR REQUIREMENTS
The requirements for providing air for combustion and ventilation
are listed in the National Fuel Gas Code NFPA 54/ANSI Z223.1 (in
Canada: CAN/CGA B149). Most homes will require that outside
air be supplied to the heated area by means of ventilation grilles
or ducts connecting directly to the outside or spaces open to the
outdoors such as attic or crawl space. The only exception is when
the furnace area meets the requirements and definitions for an
unconfined space with adequate air infiltration.
WARNING: Danger of property damage, bodily
injury or loss of life. The furnace and any other fuel-
burning appliances must be provided with enough
fresh air for proper combustion and ventilation of
flue gases. Most homes will require that outside air
be supplied into the heated area.
All air openings and connecting ducts must comply with the
following:
If the furnace is installed in an area with another gas appliance(s),
the total input rating of all appliances must be considered when
determining the free area requirements for combustion and
ventilation air openings.
Ducts must have the same cross-sectional area as the free area
of the openings to which they connect. The minimum dimension
of rectangular air ducts must not be less than 3-inches in length or
height.
LOUVERS / GRILLES AND SCREENS COVERING
FREE AREA OPENINGS
If a screen is used to cover the opening(s), it must not be smaller
than 1/4-inch mesh. Use the free area of a louver or grille to
determine the size opening required to provide the free area
specified. If the free area is not known, assume a 20% free area
for wood and a 60% free area for metal louvers or grilles.
EXAMPLE 1
FURNACE LOCATED IN UNCONFINED SPACE.
An unconfined space must have a volume of a minimum 50 cubic
feet per 1000 Btu/hr. of total of all appliances in area. Adjoining
rooms may be included only if there are no doors between the
rooms, or if special provisions are made such as ventilation grilles
installed between connecting rooms.
Page 10, Fig 6 shows the minimum area in square feet' based on
8 foot ceiling heights, required for different Btu/hr. input ratings.
A. If your furnace is in an open area (unconfined space*) the
air that leaks through the cracks around doors and windows
may be enough for combustion and ventilation air. The doors
should not fit tight. The cracks around windows should not
be caulked or weather stripped.
To determine if infiltration air is adequate, perform following
checks:
1. Close all doors and windows. If you have a fireplace,
start a fire and wait until flames are burning vigorously.
2. Turn on all exhausting devices, such as:
kitchen and bathroom exhaust fans
dryers (gas and electric)
3. Turn on all vented gas appliances, such as:
heating equipment including any room heaters,
water heater/stoves.
4. Wait ten (10) minutes for drafts to stabilize.
5. Check for draft hood spillage at each appliance. (Hold a
lighted match 2 inches from draft opening. See Fig. 4.)
B. No Spillage
If the match flame pulls toward draft hood - this indicates
sufficient infiltration air:
1. Return exhausting devices and appliances to the
condition you found them.
C. Draft Hood Spills
If there is spillage at a draft hood (match goes out or flame
wavers away from draft hood):
1. Check for plugged flue connectors and chimneys. Check
and repair, stoppage and test again.
2. If you have a fireplace, open a window or door near the
fireplace and then check for spillage.
a) If spillage stops, do not use the fireplace without a
nearby window or door open until you can supply
fresh air by a permanent duct.
3. If you have kitchen and bathroom exhaust fans, turn
them off and check for spillage.
a) If spillage stops, do not use exhaust fans until you
can supply fresh air by a permanent duct.
WARNING: Danger of property damage, bodily
injury or loss of life. Draft hood spillage, with
unobstructed vents, indicates that additional air
must be brought into the structure from outside.
Keep a window open (minimum 2 inches) near the
appliance until a permanent air duct is installed.
FIGURE 4 Draft Hood Spillage