Bard Bayrd Furnace 403293A - Manual (Page 58)

EXAMPLES USING SINGLE
APPLIANCE VENTING TABLES
Example 1; Single Draft-Hood-Equipped Appliance
Suppose that an installer has a 120,000 8tu/hr input
apptiafx:e with a 5 inch diameter draft hood outlet that
needs to be vented into a 10 foot high Type В vent
system. What size vent should be used assuming (a) a 5-
Ft lateral single-wall metal vent connector is used with
two 90° elbows, (b) a 5-Ft lateral single-wall metal vent
connector is used with three 90° elbows in the vent
system?
Solution
Table 2 should be used to solve this problem because
single-wall metal vent connectors are being used with a
Type В vent: Refer to Figure 4 of Typical Applications.
(a) Read down the first column in Table 2 until the row
associated with a 10-Ft height and 5-Ft lateral is
found. Read across this row until a vent capacity
greater than 120,000 Btu/hr is located in the
shaded columns labeled "NAT Max" tor dratt-hood-
equipped appliances. In this case, a 5 inch
diameter vent has a capacity of 122,000 Btu/hr and
may be used for this ai^lication.
(b) If three 90° elbows are used in the vent system,
then the maximum vent capacity listed in the tables
rTMJst be reduced by 10 percent (see Note 3). This
implies that the 5 inch diameter vent has an
adjusted capacity of only 110,000 Btu/hr. in this
case, the vent system must be increased to 6
inches in diameter. See calcutations below:
122,000 X .90 * 110,000 for 5" Vent
From Table 2 - Select 6" Vent
186,000 X .90 =! 167,000; This is greater than the
required 120,000, therefore use a 6" Vent and
connector when three elbows are used.
Example 2: Single Fan-Assisted Appliance
Suppose an installer has an 80,000 Btu/hr input fan-
assisted ai:^liance that must be installed using 10 feet of
lateral connector attached to a 30-Ft high Type В vent.
Two 90° elbows are needed for the installation. Can a
single-wall metal vent connector be used for this
application?
Solution
Table 2 refers to the use of single-wall metal vent
connectors with Type 8 vent. In the first column find the
row associated with a 30-Ft height and a 10-Ft lateral.
Read across this row, looking at the "FAN Min" and "FAN
Max" columns, to find that a 3 inch diameter single-wall
metal connector vent is not recommended. Moving to
the next larger size sii^le wall connector (4") we find that
a 4 inch diameter single-wall metal connector has a
recommended minimum vent capacity of 91,000 Btu/hr
and a recommended maximum vent capacity of 144,000
Btu/hr. The 80,000 Btu/hr fan-assisted appliance is
outside this range, so we conclude that a single-wall
metal vent connector cannot be used to vent this
appliance using 10 feet of lateral for the connector.
However, we see that if the 80,000 Btu/hr input
appliance could be moved to within 5 feet of the vertical
vent, then a 4 inch single-wall metal connector could be
used to vent the appliance. Table 2 shows the
acceptable range of vent capacities for a 4 inch vent with
5 feet of lateral to be between 72,000 Btu/hr and
157.000 Btu/hr.
If the appliance cannot be moved closer to the vertical
vent, then Type В vent could be used as the connector
material. In this case .Table 1 shows that (or a 30-Ft high
vent with 10 feet of lateral, the acceptable range of vent
capacities for a 4 inch diameter vent attached to a fan-
assisted appliance are between 37,000 Btu/hr and
150.000 Btu/hr.
56
EXAMPLE 2
10’ Lateral ■
30
О
Fan Assisted Appriance
00,000 BTUH Input