Lennox Merit Series Installation Instructions Manual page 12

16 − Vent connectors serving Category I appliances shall
not be connected to any portion of mechanical draft
systems operating under positive pressure such as
Category III or IV venting systems.
17 − If vent connectors are combined prior to entering the
common vent, the maximum common vent capacity
listed in the common venting tables must be reduced by
10%, the equivalent of one 90° elbow (0.90 x maximum
common vent capacity).
18 − The common vent diameter must always be at least as
large as the largest vent connector diameter.
19 − In no case, shall the vent connector be sized more than
Capacity of Type B Double−Wall Vents with Type B Double−Wall Connectors
Height Lateral
H L
(m) (m)
0
0.6
1.8
1.2
1.8
0
0.6
2.4
1.5
2.4
0
0.6
3.0
1.5
3.0
0
0.6
1.5
4.5
3.0
4.5
0
0.6
1.5
6.0
3.0
4.5
6.0
0
0.6
1.5
9.0 3.0
4.5
6.0
9.0
NOTE − Single appliance venting con gurations with zero lateral lengths are assumed to have no elbows in the vent system. For all other
vent con gurations, the vent system is assumed to have two 90° elbows. For each additional 90° elbow or equivalent (for example two 45°
elbows equal one 90° elbow) beyond two, the maximum capacity listed in the venting table should be reduced by 10 percent (0.90 x maxi-
mum listed capacity).
12
Serving a Single Category I Appliance
76mm
Appliance Input Rating in Thousands of Btu Per Hour
MIN MAX MIN
0 78
13 51
21 49
25 46
0 84
12 57
23 53
28 49
0 88
12 61
23 57
30 51
0 94
11 69
22 65
29 59
35 53
0 97
10 75
21 71
28 64
34 58
48 52
0 100
9 81
21 77
27 70
33 64
56 58
NA NA
VENTING
two consecutive table size diameters over the size of
the draft hood outlet or ue collar outlet.
20 − Do not install a manual damper, barometric draft regu-
lator or ue restrictor between the furnace and the
chimney.
21 − When connecting this appliance to an existing dedi-
cated or common venting system, you must inspect the
venting system's general condition and look for signs
of corrosion. The existing vent pipe size must conform
to these instructi o ns and the provided venting tables. If
the existing venting system does not meet these re-
quirements, it must be resized.
Vent and Connector Diameter − D (mm)
100mm
MAX MIN
0 152
18 97
30 94
36 91
0 165
16 109
32 103
39 98
0 175
17 118
32 113
41 104
0 191
15 136
30 130
40 121
48 112
0 202
14 149
29 143
38 133
46 124
55 116
0 213
13 166
28 160
37 150
44 141
53 132
73 113
125mm
MAX MIN
0 251
27 157
39 153
47 149
0 276
25 178
42 171
51 164
0 295
23 194
41 187
54 176
0 327
20 226
39 219
51 206
61 195
0 349
18 250
38 242
50 229
59 217
69 206
0 374
14 283
36 275
48 262
57 249
66 237
88 214 104
150mm
MAX
0 375
32 232
50 227
59 223
0 415
28 263
53 255
64 247
0 447
26 289
52 280
67 267
0 502
22 339
49 330
64 315
76 301
0 540
20 377
47 367
62 351
73 337
84 322
0 587
18 432
45 421
59 405
70 389
80 374
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