Equivalent Duct Lengths for Commonly
Used Transitions
Duct Piece
Smooth, straight
3¼" x 10", straight
3¼" x 14", straight
90° elbow , round
45° elbow , round
3¼" x 10",
90° elbow , round
3¼" x 10",
45° elbow , round
3¼" x 10", Flat elbow
Round to 3¼" x 10"
3¼" x 10" to round
Equivalent
Size (in)
Length (ft)
6
1.2
8
0.7
10
0.6
N/A
1
N/A
0.7
6
12
8
6
10
5
6
5
8
3
10
2
N/A
5
N/A
15
N/A
20
6
1
8
10
6
5
8
2
NOTE: These commonly used installation parts can be purchased at a
local hardware store. Thermador does not manufacture all these parts.
Duct Piece
Round to 3¼" x 10"
90° elbow ,
3¼" x 10" to round
90° elbow ,
3¼" x 10" Center
reverse elbow , left
3¼" x 10", Center
reverse elbow , right
3¼" x 10", Left
reverse elbow
3¼" x 10", Right
reverse elbow
Round wall cap
Round roof cap
2' long, 3¼" x 10" ex
3¼" x 10", Roof jack
and shutter
Equivalent
Size (in)
Length (ft)
6
10
6
10
N/A
15
N/A
25
N/A
15
N/A
25
6
2
8
2
10
2
6
2
8
2
10
2
N/A
20
N/A
2
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