B. Using 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.

Measure the shift needed to avoid the overhead obstruction. Refer to dimension A in Figure 8.3.

Find the appropriate A dimension listed in Table 8.2.

The B dimension coinciding with the A dimension measurement in Table 8.2 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.

A

B

1-1/4 in. (32 mm)

OVERLAP

Figure 8.3 Chimney Offset/Return

Example:

Your “A” dimension from Figure 8.3 is 14 1/2 in. (368 mm). Using Table 8.2 the dimension closest to, but not less than 14 1/2 in. (368 mm) is 15 3/4 in. (400 mm) using a 30° offset/return.

You determined from the table that you would need

36 5/8 in. (930 mm) (Dimension “B”) between the offset and return.

The chimney component that best fits your application is two SL1112s.

Table 8.2

 

A

 

B

 

 

 

 

 

in.

 

mm

in.

 

mm

SL1106

SL1112

SL1118

SL1136

SL1148

4 7/8

 

124

17 7/8

 

454

-

-

-

-

-

7 1/4

 

184

22

 

559

1

-

-

-

-

 

 

 

 

 

 

 

 

 

 

 

9 3/4

 

248

26 1/8

 

664

2

-

-

-

-

10 1/4

 

260

27 1/4

 

692

-

1

-

-

-

 

 

 

 

 

 

 

 

 

 

 

12 3/4

 

324

31 3/8

 

797

1

1

-

-

-

13 1/4

 

337

32 3/8

 

822

-

-

1

-

-

 

 

 

 

 

 

 

 

 

 

 

15 3/4

 

400

36 5/8

 

930

-

2

-

-

-

18 1/8

 

460

40 3/4

 

1035

1

2

-

-

-

18 3/4

 

476

41 3/4

 

1060

-

1

1

-

-

 

 

 

 

 

 

 

 

 

 

 

21 3/4

 

552

47

 

1194

-

-

2

-

-

22 1/4

 

565

4 8

 

1219

-

-

-

1

-

 

 

 

 

 

 

 

 

 

 

 

24 3/4

 

629

52 1/8

 

1324

1

-

-

1

-

27 3/4

 

705

57 3/8

 

1457

-

1

-

1

-

 

 

 

 

 

 

 

 

 

 

 

28 1/4

 

718

58 3/8

 

1483

-

-

-

-

1

30 3/4

 

781

62 1/2

 

1588

1

-

-

-

1

 

 

 

 

 

 

 

 

 

 

 

33 3/4

 

857

67 3/4

 

1721

-

1

-

-

1

 

 

 

 

 

 

 

 

 

 

 

36 3/4

 

933

73

 

1854

-

-

1

-

1

39 3/4

 

1010

78 1/8

 

1984

-

-

-

2

-

 

 

 

 

 

 

 

 

 

 

 

41 1/8

 

1045

82 3/8

 

2092

1

-

-

2

-

45 3/4

 

1162

88 1/2

 

2248

-

-

-

1

1

 

 

 

 

 

 

 

 

 

 

 

48 1/8

 

1222

92 3/4

 

2356

1

-

-

1

1

51 3/4

 

1314

98 7/8

 

2511

-

-

-

-

2

Proper assembly of air cooled chimney parts results in an overlap of chimney joints of 1-1/4 in. (32 mm). Effective length is built into this table.

26

Heatilator • Birmingham BIR42 • 4059-308 Rev F • 11/08

Page 26
Image 26
Hearth and Home Technologies BIR42 owner manual Using Offsets/Returns, Example