Williams 2509622 Owner's Manual page 9

Installing Your Furnace
Combustion & Ventilation Air (continued)
FURNACE LOCATED IN UNCONFINED SPACE
An unconfined space must have a volume of a minimum 50 cubic
feet per 1,000 Btu/hr. of the total combined input of all appliances
in the 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. Figure
4 outlines the minimum area in square feet, based on 8-foot
ceiling heights for various Btu/hr. input ratings.
FURNACE LOCATED IN CONFINED SPACE
If a furnace is installed in a confined space, it must be provided
with free air for proper combustion and ventilation of flue gases by
one of the following methods:
Examples of Grille Placement
Max.
Btu/hr.
Input
A. Air From Inside the Building
If the confined space adjoins an unconfined space, provide two
permanent openings. One within 12-inches of the top and another
within 12-inches of the bottom of the room directly connected to
the unconfined space. Each opening must have a free area of at
least 100-square inches or 1-square inch per 1,000 Btu/hr. of
input for all appliances combined.
WARNING: Danger of property damage, bodily
injury or death. The adjoining unconfined space
must have adequate air infiltration.
B. Air From Outdoors
If confined space does not adjoin an unconfined space, then air
must be provided from outdoors or spaces open to the outdoors
such as an attic or crawl spaces.
Openings for inlet or outlet air should NOT be made into an attic
area if the attic is equipped with a thermostat controlled power
vent.
Provide two permanent openings, one within 12-inches of the top
and bottom of the room connecting directly to, or by using ducts,
with the outdoors or areas open to fresh air.
If the opening connects directly to, or with vertical ducts, the free
area of each opening must be at least 1-square inch per 4,000
Btu/hr. of the combined input of all appliances in the area.
If horizontal ducts are used, the free area of each opening must
be at least 1-square inch per 2,000 Btu/hr. of the combined input
of all appliances in the area.
WARNING: Danger of illness, bodily injury or
death. Draft hood spillage, with unobstructed vents,
indicates that additional air must be brought into the
structure from the outside. Keep a window open
(minimum 2-inches) near the appliance until a
permanent air duct is installed.
Examples of Air Inlets and Outlets