Brochure

8
Draft Control
Simple rules of thumb to guide size selections:
1. For most applications, the draft control should be the
same size as the flue pipe. In other words, use a 6"
control for a 6" pipe.
2. If the flue pipe or breaching is square, use the round
equivalent. For example - on a 14" x 14" breaching use a
14" control. Little flow occurs in the corners of a square
pipe, so its capacity is approximately the same as a round
pipe of the same diameter.
3. If the breaching is rectangular
or oval, compute its cross-
sectional area and select a
draft control having the same
or a greater nominal cross-
sectional area. A breaching 14"
high x 10" wide would have a
cross-sectional area of 140
square inches. From the table,
select a 14" control with a
cross-sectional area of 154
square inches.
4. Where a control larger than
32" is required, use more than
one draft control with
combined cross-sectional areas
equal to or greater than that of
the breaching.
5. When chimneys are of an
unusual height, or if the draft
to be maintained is either very
high or very low, it is advisable
to deviate from the rules of
thumb outlined here and refer
to the sizing chart.
Choosing The Right Size
(Sizing the Control)
Control
Size
Nominal
Cross-Sectional
Area (Sq. In.)
Control
Size
Nominal
Cross-Sectional
Area (Sq. In.)
6" 28 16" 201
7" 38 18" 255
8" 50 20" 314
9" 63 24" 452
10" 78 28" 616
12" 113 32" 804
14" 154
Sizing Chart
Diameter
of Flue or
Breeching
If
Chimney
Height is
Use
This Size
Control
If
Chimney
Height is
Use
This Size
Control
If
Chimney
Height is
Use
This Size
Control
4 15' or less 4" 16' or more 5"
5 15' or less 5" 16' or more 6"
6 15' or less 6" 16' or more 7"
7 15' or less 7" 16' or more 8"
8 15' or less 8" 16' or more 9"
9 15' or less 9" 16'-30' 10" 31' or more 12"
10 20' or less 10" 21'-40' 12" 41' or more 14"
11 20' or less 12" 21'-40' 12" 41' or more 14"
12 20' or less 12" 21'-40' 14" 41' or more 16"
13 22' or less 14" 23'-45' 16" 46' or more 18"
14 22' or less 14" 23'-45' 16" 46' or more 18"
15 22' or less 16" 23'-45' 16" 46' or more 18"
16 30' or less 16" 31'-50' 18" 51' or more 20"
17 30' or less 18" 31'-50' 20" 51' or more 20"
18 30' or less 18" 31'-50' 20" 51' or more 20"
19 30' or less 20" 31'-50' 20" 51' or more 24"
20 30' or less 20" 31'-50' 20" 51' or more 24"
21 30' or less 20" 31'-50' 24" 51' or more 24"
22 30' or less 24" 31'-50' 24" 51' or more 24"
23 35' or less 24" 36'-60' 24" 61' or more 28"
24 35' or less 24" 36'-60' 24" 61' or more 28"
25 35' or less 28" 36'-60' 28" 61' or more 28"
26 40' or less 28" 41'-70' 28" 71' or more 28"
27 40' or less 28" 41'-70' 28" 71'-100' 28"
28 50' or less 28" 51'-100' 32" 100' or more 32"
29 50' or less 28" 51'-100' 32" 100' or more 32"
30 50' or less 32" 51'-100' 32" 100' or more 32"
31 50' or less 32" 51'-100' 32" 100' or more Two 24"
32 50' or less 32" 51'-100' 32" 100' or more
One 24"
One 28"
33 50' or less 32" 51'-100'
One 32"
One 20"
100' or more
One 32"
One 24"
34 50' or less 32" 51'-100'
One 32"
One 24"
100' or more
One 32"
One 24"