Carrier UPFLOW 58BTA - Manual (Page 3)

In unconfined spaces in buildings of conventional frame,
brick or stone construction infiltration may be adequate to
provide air for combustion, ventilation and dilution of flue
/--xgases. This determination must be made on an individual
( hstallation basis and must take into consideration the
overall volume of the unconfined space, the number of
windows and ventilation openings, the number of doors to
the outside, internal doors which can close off the
unconfined space and the overall tightness of the building
construction.
Many new buildings and homes (and older ones that have
been weatherized) must be considered as being tight
construction and, therefore, infiltration will not be sufficient
to supply the necessary air for combustion and ventilation.
A building can be considered as being of tight
construction when:
a. Walls and ceilings exposed to the outside
atmosphere have a continuous water vapor
retarder with a rating of one perm or less with
openings gasketed or sealed and /or
b. Weatherstripping has been added on operable
windows and doors, and/or
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 fuel lines and at other
openings.
If combustion and ventilation air must be supplied to an
unconfined space from outside, an opening with a free
area of not less than one square inch per 1,000 BTU per
hour of total input of all appliances within the unconfined
space (but not less than 100 square inches) must be
provided. This opening must be located such that it can
not be blocked at any time.
For a confined space, where air is taken from an interior
space, two permanent openings of equal area are
required. One opening must be within 12" of the ceiling
and the other within 12" of the floor. Each opening must
have a free area of at least 1 sq. inch per 1,000 BTU of
total input rating but no less than 100 sq. inches.
If outside air is supplied to a confined space, then the two
openings must be equal and located as above and the
free area of each must be:
1. 1 sq. inch per 4,000 BTU of total rating when the
air is directly communicated from the outdoors.
2. 1 sq. inch per 4,000 BTU of total input rating
\ when the air is brought in through vertical ducts.
3. 1 sq. inch per 2,000 BTU of total input rating
when the air is transferred through horizontal
ducts.
When ducts are used to supply air, they must be of 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 calculating free area, consideration shall be given to
the blocking effect of louvers, grilles or screens protecting
openings. Screens used shall not be smaller than 1/4
inch mesh and shall be readily accessible for cleaning.
If the free area through a design of louvered or grille is
known, it shall be used in calculating the size design and
free area specified. If the design and free area is not
known, it may be assumed that wood louvers will have 20
percent free area and metal louvers and grilles will have
60 percent free area. Louvers shall be fixed in the open
position or interlocked with the furnace so they are
opened automatically at furnace start-up and remain open
during furnace operation.
WARNING
Do not block the combustion air openings in the
furnace. Any blockage will result in improper
combustion and may result in a fire hazard and/or
cause bodily harm.
Ductwork Recommendations:
The proper sizing of warm air ducts is necessary to insure
satisfactory furnace operation. Ductwork should be in
accordance with the latest editions of NFPA-90A
(Installation of Air Conditioning and Ventilating Systems)
and NFPA-90B (Warm Air Heating and Air Conditioning
Systems) or Canadian equivalent.
The supply ductwork should be attached to the flanged
opening provided at the discharge end of the furnace.
See Figure 7 for the dimensions of this opening.
Knockouts are provided on both sides of the furnace to
facilitate the side panel cut out required to assemble the
return ductwork. This can be done on either the right or
the left side of the furnace. See Figure 7 for location and
dimensions. Undersized cut-outs will adversely affect the
airflow capability of the furnace.
When the provided external filter rack is used, the return
air duct should be attached as per Figure 9.
Provision is also made on this furnace for a bottom return
air duct. (We recommend the use of this opening for
horizontal installations.) The specifications for this
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