Bard Bayrd Furnace 403293A - Manual (Page 41)

) ) I. GENERAL VENTING REQUIREMENTS
All requirements contained in this document apply
to both Category 1 draft hood equipped and fan-
assisted combustion appliances. At no time should
a venting system for a listed Category 11, 111, or IV
appliance be sized with these Tables. The
alternate sizing methods described in the National
Fuel Gas Code (NFPA54; a NS1 Z223.V1988) may
also be used to size the venting system for a
drafthood equipped appliance. At this time,
alternate sizing methods have not been
developed for tan-assisted appliances. Therefore,
until engineering data is developed to allow
alternate sizing methods for Category I fan-
assisted appliances, the vent tables must be used.
1) The venting tables included in this instaiction
apply to vents and chimneys internal to the
structure below the roof tine. Exterior
chimneys or vents not enclosed by the
structure or a chase below the roof line may
experience
continuous condensation
depending on locality. Consult local gas
utility, appliance manufacturer and/or local
codes. A chimney with one or more sides
exposed to the outside of the structure is
considered to be an exterior chimney. A
Type B or listed chimney lining system
passing through an unused masonry chimney
flue is not considered to be exposed to the
outdoors
2) If the vent or connector size determined from
the tables is smaller than the appliance
drafthood outlet or flue collar, the smaller size
may be used provided:
^ The total vent height "FT is at least 10 FT.
b) Vents or connectors for appliance
drafthood outlets or flue collars 12
inches in diameter or smaller are not
reduced more than one table size (e.g.
12 inches to 10 inches is a one size
reduction).
c) Vents or connectors for appliance
drafthood or flue collars above 12
inches in diameter are not reduced
more than two table sizes (e.g. 24
inches to 20 inches is a two size
reduction).
d) The maximum capacity listed in the
tables for a fan-assisted appliance is
reduced by 10% (0.90 x maximum
capacity).
e) The drafthood outlet is greater than 4
inches in diameter. Do not connect a 3
inch diameter vent or connector to a 4
inch diameter drafthood outlet. This
provision does not apply to fan-assisted
appliances.
3) Single appliance venting configurations with
zero lateral lengths, Tables 1 & 2, are
assumed to have no elbows in the vent
system. For all other vent configurations, the
vent system is assumed to have two 90®
elbows. For each additional 90® elbow, or
equivalenr beyond two, the maximum
capacity listed in the venting table should be
reduced by 10 percent (0.90 x maximum
listed capacity).
* Two 45® elbows are equivalent to one 90® elblow.
4) The common venting Tables 3, 4, 7, & 8 were
generated using a maximum horizontal vent
connector length of 1 1/2 feet (18 inches) for
each inch of connector diameter as follows:
CONNECTOR DIAMETER MAXIMUM HORIZONTAL
CONNECTOR LENGTH
(INCHES) (FEET)
3 4 1/2
4 6
5 7 1/2
6 9
7 10 1/2
8 12
9 13 1/2
10 15
12 18
14 21
16 24
18 27
20 30
22 33
24 36
The vent connector should be routed to the
vent utilizing the shortest possible route.
Connectors with longer horizontal lengths than
those listed above are possible under the
following conditions:
a. The maximum capacity (Fan Max. or Nat
Max.)of the vent connector shall be
reduced 10% for each additional multiple
of the length listed above. For example,
the maximum length listed above for a 4
inch connector is 6 feet. With a connector
length greater than 6 feet but not
exceeding 12 feet, the maximum capacity
must be reduced by 10% (0.90 x maximum
vent connector capacity). With a
connector length greater than 12 feet but
not exceeding 18 feet, the maximum
capacity must be reduced by 20% (0.80 x
maximum vent capacity).
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