DUCT EQUIVALENT NUMBER
PIECES LENGTH x USED = TOTAL
31⁄4″x 10″1 Ft. x ( ) = Ft.
Rect.,
straight
7″Round, 1 Ft. x ( ) = Ft.
straight
6″Round, 1 Ft. x ( ) = Ft.
straight
31⁄4″x 10″8.5 Ft. x ( ) = Ft.
Rect. 90°
elbow
31⁄4″x 10″7 Ft. x ( ) = Ft.
Rect. 45°
elbow
31⁄4″x 10″24 Ft. x ( ) = Ft.
Rect. 90°
flat elbow
31⁄4″x 10″45 Ft. x ( ) = Ft.
Rect.
(7 ft. w/o
wall cap
damper)
x ( ) = Ft.
with
damper
31⁄4″x 10″4.5 Ft. x ( ) = Ft.
Rect. to
6″round
transition
31⁄4″x 10″11.5 Ft. x ( ) = Ft.
Rect. to
6″round
transition
90° elbow
6″Round, 8 Ft. x ( ) = Ft.
90° elbow
6″Round, 6.5 Ft. x ( ) = Ft.
45° elbow
Subtotal column 1 = Ft.
8
WORKSHEET—CALCULATE TOTAL EQUIVALENT DUCTWORK LENGTH
DUCT EQUIVALENT NUMBER
PIECES LENGTH x USED = TOTAL
6″Round 34 Ft. x ( ) = Ft.
wall cap
(6 ft. w/o
with
damper)
x ( ) = Ft.
damper
6″Round 30 Ft. x ( ) = Ft.
roof cap
6″Round 5.5 Ft. x ( ) = Ft.
to
31⁄4″x 10″
rect.
transition
6″Round 14.5 Ft. x ( ) = Ft.
to
31⁄4″x 10″
rect.
transition
90° elbow
7″Round, 8 Ft. x ( ) = Ft.
90° elbow
7″Round, 6.5 Ft. x ( ) = Ft.
45° elbow
7″Round 34 Ft. x ( ) = Ft.
wall cap (
6 ft. w/o
with
damper)
x ( ) = Ft.
damper
7″Round 30 Ft. x ( ) = Ft.
roof cap
7″Round 5.5 Ft. x ( ) = Ft.
to
31⁄4″x 10″
rect.
transition
7″Round 14.5 Ft. x ( ) = Ft.
to
31⁄4″x 10″
rect.
transition,
90° elbow
Subtotal column 2 = Ft.
Subtotal column 1 = Ft.
Total ductwork = Ft.
Installation Instructions
MAXIMUM DUCT LENGTH: For satisfactory air
movement, the total duct length of a 31⁄4″x 10″
rectangular, 6″or 7″diameter round duct should
not exceed 65 equivalent feet.