Bryant 350MAV Installation, Start-Up, And Operating Instructions Manual page 31

TABLE 7—MAXIMUM ALLOWABLE EXPOSED VENT PIPE LENGTH (FT) WITH AND WITHOUT INSULATION IN WINTER
WINTER DESIGN
UNIT
TEMPERATURE
SIZE
040
060
080
100
120
140
* Pipe length (ft) specified for maximum pipe lengths located in unconditioned spaces. Pipes located in unconditioned space cannot exceed total allowable pipe length as
specified in Table 6.
† Insulation thickness based on R value of 3.5 (ft_ • °F• hr)/(Btu•in.)
Fig. 35—Rooftop Termination (Dimension "A" is Touching or 2-in. Maximum Separation)
NOTE: If 115-v power supply to furnace or blower access panel
switch is interrupted during a call for heat, blower operates for 90
sec when power is restored before heating cycle is resumed.
A. HEATING MODE
When wall thermostat calls for heat, R-W circuit closes. Furnace
control performs a self-check, verifies pressure switch contacts are
open, and starts inducer motor.
DESIGN TEMPERATURE AMBIENT*
MAX PIPE
DIAMETER
(°F) (IN.)
20 1.5
0 1.5
-20 1.5
20 2
0 2
-20 2
20 2
0 2
-20 2
20 2
0 2
-20 2
20 2.5
0 2.5
-20 2.5
20 2.5
0 2.5
-20 2.5
20 3
0 3
-20 3
20 3
0 3
-20 3
20 4
0 4
-20 4
20 3
0 3
-20 3
20 4
0 4
-20 4
WITHOUT
INSULATION
51
28
16
45
22
10
65
35
20
55
48
30
70
47
28
40
40
38
70
50
28
70
61
37
70
48
23
60
60
44
70
57
30
A
1. Prepurge period—As inducer motor comes up to speed,
pressure switch contacts close to begin a 15-sec prepurge
period.
2. Ignitor warm up—At end of prepurge period, ignitor is
energized for a 17-sec ignitor warm-up period.
3. Ignition sequence—When ignitor warm-up period is com-
pleted, gas valve opens, permitting gas flow to burners
—31—
WITH 3/8–IN. OR
THICKER INSULATION†
70
70
70
70
70
58
70
70
70
55
55
55
70
70
70
40
40
40
70
70
70
70
70
70
70
70
70
60
60
60
70
70
70
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