PLB
Oil Furnaces
–
Furnace Manual
4
670-000-001/0204
1
Prepare furnace location
(continued)
Air for combustion and ventilation
Adequate combustion and ventilation air ensures
proper combustion and reduces risk of severe
personal injury or death from possible flue gas
leakage and carbon monoxide emissions.
Do not install exhaust fan in furnace room.
Consider building construction
Older buildings with single-pane windows, minimal weather-stripping
and no vapor barrier often provide enough natural infiltration and
ventilation without dedicated openings.
New construction or remodeled buildings are most often built tighter.
Windows and doors are weather-stripped, vapor barriers are used
and openings in walls are caulked. As a result, such tight
construction is unlikely to allow proper natural air infiltration and
ventilation.
For buildings with tight construction, provide openings directly to
outside or to a ventilated crawl space or attic. Size the openings to
the same specifications as for the furnace location per the following
paragraphs.
Follow state, provincial or local codes when sizing adequate
combustion and ventilation air openings. In absence of codes, use
the following guidelines when furnace is in a confined room (defined
by NFPA 31 as less than 7200 cubic feet per 1 GPH input of all
appliances in area. A room 8 ft. high x 30.0 ft. x 30.0 ft. is 7200 cu.
ft.).
Provide two permanent openings
Openings locations
One within 12 inches of ceiling, one within 12 inches of floor.
Minimum height or length dimension of each rectangular opening
should be at least 3 inches.
When inside air is used
Each opening must freely connect with areas having adequate
infiltration from outside. Each opening should be at least 140 sq. in.
per 1 GPH input (1 sq. in. per 1000 BTU input) of all fuel-burning
appliances plus requirements for any equipment that can pull air
from room (including clothes dryer and fireplace).
When outside air is used
Connect each opening directly, by ducts to the outdoors, or to crawl
or attic space that freely connects with outdoors. Size per below :
x
Through outside wall or vertical ducts – at least 35 sq. in. per 1
GPH input (1sq. in. per 4000 BTU input) of all fuel burning
appliances plus requirements for any equipment that can pull air
from room (including clothes dryer and fireplace).
x
Through horizontal ducts – at least 70 sq. in. per 1 GPH furnace
input (1 sq. in. per 2000 BTU input) of all fuel-burning appliances
plus requirements for any equipment that can pull air from room
(including clothes dryer and fireplace).
x
Where ducts are used, they should have the same cross-
sectional area as free area of openings to which they connect.
Compensate for louver, grille or screen blockage when
calculating free air openings. Refer to their manufacturer’s
instructions for details. If unknown, use :
x
Wood louvers, which provide 20-25 % free air.
x
Metal louvers or grilles, which provide 60-75 % free air.
Lock louvers in open position or interlock with equipment to
prove open before furnace operation.
Basement installations
When the furnace is located in an unconfined space, such as an
unpartitioned basement, adequate air should normally be available
without additional opening. An unconfined space is defined as one
having no less than 50 cubic feet room volume per 1,000 BTU/h
input of all appliances in the space.
If the house is of tight construction, provide air openings to the
basement directly from outside or from a ventilated attic. Size the
openings as described above under “When outside air is used”.
WARNING
WARNING
