Page. 11
Equivalent Duct Lengths for Commonly
Used Transitions
Size (in)
E
q
uivalent
Len
g
th (ft)
Size (in)
E
q
uivalent
Len
g
th (ft)
6
1.2
6
10
8
0.7
10
0.6
3¼
"
x 10
"
, strai
g
ht
N/A
1
3¼
"
x 10
"
, Center
reverse el
b
ow , ri
g
ht
N/A
25
3¼
"
x 14
"
, strai
g
ht
N/A
0.7
3¼
"
x 10
"
, Left
reverse el
b
ow
N/A
15
3¼
"
x 10
"
, Ri
g
ht
reverse el
b
ow
N/A
25
6
12
6
2
8
6
8
2
10
10
2
6
5
6
2
2
5
8
3
8
2
2
2
10
10
3¼
"
x 10
"
,
90° el
b
ow , roun
d
N/A
5
2
’
lon
g
, 3¼
"
x 10
"
flex
N/A
20
3¼
"
x 10
"
,
45° el
b
ow , roun
d
N/A
15
3¼
"
x 10
"
, Flat el
b
ow
N/A
20
6
1
8
10
8
2
3¼
"
x 10
"
, Roof jack
an
d
shutter
N/A
6
5
6
10
NOTE: These commonly use
d
installation parts can
b
e purchase
d
at a
local har
d
ware store. Therma
d
or
d
oes not manufacture all these parts.
Roun
d
wall cap
Roun
d
roof cap
3¼
"
x 10
"
to roun
d
90° el
b
ow ,
Duct Piece
3¼
"
x 10
"
Center
reverse el
b
ow , left
15
N/A
Roun
d
to 3¼
"
x 10
"
3¼
"
x 10
"
to roun
d
Roun
d
to 3¼
"
x 10
"
90° el
b
ow ,
Duct Piece
Smooth, strai
g
ht
90° el
b
ow , roun
d
45° el
b
ow , roun
d
