Choosing The Right Size - Field Controls SWG-3 Product Manual

DRAFT CONTROL
SIZING THE CONTROL

CHOOSING THE RIGHT SIZE

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 vent pipe or breach is square, use the round equivalent.
For example - on a 14" x 14" breach 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 breach 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 breach 14" high x 10" wide
would have a cross-sectional
area of 140 square inches. From
Table 1, 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 breach.
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.
34
USE THIS
DIAMETER OF IF CHIMNEY
VENT OR BREACH HEIGHT IS
CONTROL
4"
15' or less
5" 15' or less
6"
15' or less
7"
15' or less
8"
15' or less
9" 15' or less
10"
20' or less
11"
20' or less
12"
20' or less
13"
22' or less
14" 22' or less
15"
22' or less
16"
30' or less
17"
30' or less
18" 30' or less
19" 30' or less
20"
30' or less
21"
30' or less
22"
30' or less
23" 35' or less
24"
35' or less
25"
35' or less
26"
40' or less
27"
40' or less
28" 50' or less
29"
50' or less
30"
50' or less
31"
50' or less
32"
50' or less
33" 50' or less
34" 50' or less
TABLE 1
NOMINAL
CONTROL CONTROL
CROSS-SECTIONAL AREA
SIZE
(SQ. IN.)
6"
28
7" 38
8"
50
9"
63
10"
78
12"
1 13
14"
154
SIZING CHART
IF CHIMNEY USE THIS
SIZE
HEIGHT IS SIZE CONTROL
4" 16' or more 5"
5" 16' or more 6"
6" 16' or more 7"
7" 16' or more 8"
8" 16' or more 9"
9" 16'-30' 10"
10" 21'-40' 12"
12" 21'-40' 12"
12" 21'-40' 14"
14" 23'-45' 16"
14" 23'-45' 16"
16" 23'-45' 16"
16" 31'-50' 18"
18" 31'-50' 20"
18" 31'-50' 20"
20" 31'-50' 20"
20" 31'-50' 20"
20" 31'-50' 24"
24" 31'-50' 24"
24" 36'-60' 24"
24" 36'-60' 24"
28" 36'-60' 28"
28" 41'-70' 28"
28" 41'-70' 28"
28" 51'-100' 32"
28" 51'-100' 32"
32" 51'-100' 32"
32" 51'-100' 32"
32" 51'-100' 32"
One 32"
32" 51'-100'
One 20"
One 32"
32" 51'-100'
One 24"
Customer Service:
NOMINAL
CROSS-SECTIONAL AREA
SIZE
(SQ. IN.)
16"
201
18" 255
20"
314
24"
452
28"
616
32"
804
IF CHIMNEY USE THIS
HEIGHT IS SIZE CONTROL
31' or more 12"
41' or more 14"
41' or more 14"
41' or more 16"
46' or more 18"
46' or more 18"
46' or more 18"
51' or more 20"
51' or more 20"
51' or more 20"
51' or more 24"
51' or more 24"
51' or more 24"
51' or more 24"
61' or more 28"
61' or more 28"
61' or more 28"
71' or more 28"
71'-100' 28"
100' or more 32"
100' or more 32"
100' or more 32"
100' or more Two 24"
One 24"
100' or more
One 28"
One 32"
100' or more
One 24"
One 32"
100' or more
One 24"
252.522.3031