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B. Offsets/Returns
•
Use an offset/return to bypass overhead obstructions.
•
An offset and return can be used as a single entity or separated by chimney section(s).
WARNING! Risk of Fire! DO NOT use offset/returns greater than 30°. Chimney draft will be restricted and could cause
overheating and fire. Secure offsets with screws ( not to exceed 1/2" / 13 mm in length) Secure returns with strapping.
Straight chimney sections may be secured with screws. Keep chimney sections from separating or twisting.
•
Measure the shift needed to avoid the overhead obstruction. Refer to dimension A in Figure 4.2.
•
Find the appropriate A dimension listed in Table 4.3. The B dimension coinciding with the A dimension measurement in
Table 4.3 represents the required vertical clearance needed to complete the offset/return.
•
Read across the chart to find the number of chimney sections/model numbers needed between the offset and return.
Figure 4.2
Chimney Offset/Return
Table 4.3 Offset Dimensions
15-degree
A
B
in.
mm
in.
mm
1 5/8
41
13 3/8
340
2 7/8
73
17 3/4
451
4 1/8
102
22 3/8
568
4 1/2
114
23 5/8
600
5 3/4
146
28 1/4
718
6
152
29 3/8
746
7 1/4
184
34
864
7 3/4
197
36 1/8
918
8 3/4
222
39 3/4
1010 16 1/4
10 3/8
264
45 5/8
1159 19 1/4
10 5/8
270
46 3/4
1187 20 1/2
11 7/8
302
51 3/8
1305 22 1/4
13 1/2
243
57 1/4
1454 25 1/4
13 3/4
349
58 3/8
1483 26 1/2
15
381
63
1600 28 1/4
16 1/2
419
68 3/4
1746 31 1/4
18
457
74 5/8
1895 34 1/4
19 5/8
498
80 3/8
2042 37 1/4
20 5/8
524
84 1/8
2137 39 1/8
22 3/4
578
91 7/8
2334 43 1/4 1099 84 1/8 2137
24
610
96 1/2
2451 45 1/8 1146 87 1/4 2216
25 7/8
657
103 1/2 2629 49 1/4 1251 94 1/2 2400
Proper assembly of air-cooled chimney parts result in an overlap at chimney joints of 1-1/4 in. (32 mm). Effective
length is built into this chart.
12
Heatilator • MEL36, MEL42 Installation Manual • 4044-212 • Rev D • 01/06/15
A
B
1-1/4 in. (32 mm)
OVERLAP
30-degree
A
B
in.
mm
in.
mm
3 5/8
92
15 1/2
394
5 1/2
140
18 5/8
473
7 1/4
184
21 3/4
552
8 1/2
216
23 3/4
603
10 1/4
260
27
686
11 1/2
292
29
737
13 1/4
337
32 1/8
816
14 1/2
368
34 1/8
867
413
37 3/8
949
489
42 1/2 1080
521
44 5/8 1133
565
47 3/4 1213
641
52 7/8 1343
673
55
1397
718
58 1/8 1476
794
63 1/4 1607
870
68 1/2 1740
946
73 3/4 1873
994
76 7/8 1953
Example:
Your "A" dimension from Figure 4.2 is 14-1/2 in. (368
mm). Using Table 4.3, the dimension closest to, but not
less than 14-1/2 in. (368 mm) is 14-1/2 in. (368 mm) us-
ing a 30° offset/return.
You determine from the table that you need 34-1/8 in.
(867 mm) (Dimension "B") between the offset and re-
turn.
The chimney component that best fits your application is
one SL324.
SL306 SL312 SL318 SL324 SL336 SL348
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