GE PGP989 - Ductwork Calculations

20



Equivalent Number Equivalent
Duct Pieces Length* x Used = Length
6” round
straight 1 ft x ( )
†
= ft
3
1
⁄4” x 10"
straight 1 ft x ( )
†
= ft
6”, 90°
elbow 15 ft x ( ) = ft
6”, 45°
elbow 9 ft x ( ) = ft
24” max
flexible
metal offset
adapter 34 ft x ( ) = ft
3
1
⁄4” x 10”
90° elbow 16 ft x ( ) = ft
3
1
⁄4” x 10”
45° elbow 5 ft x ( ) = ft
3
1
⁄4” x 10”
90° flat elbow 18 ft x ( ) = ft
6” round
to 3
1
⁄4” x 10”
transition 7 ft x ( ) = ft
Subtotal Column 1 = ft
* Equivalent lengths of duct pieces are based on actual
tests and reflect requirements for good venting
performance with any downdraft cooktop
† Measure and list feet of straight duct used Count and
list the quantity of all other duct pieces for the “Number
Used” of each type

For maximum efficiency, use the shortest and straightest
duct run possible, with as few fittings as possible


Venting performance is improved by using larger
diameter duct
Equivalent Number Equivalent
Duct Pieces Length* x Used = Length
6” round
to 3
1
⁄4” x 10”
transition
90° elbow 20 ft x ( ) = ft
3
1
⁄4” x 10”
to 6” round
transition 5 ft x ( ) = ft
3
1
⁄4” x 10”
to 6” round
transition
90° elbow 12 ft x ( ) = ft
6” round
wall cap
with damper 21 ft x ( ) = ft
3
1
⁄4” x 10”
wall cap
with damper 27 ft x ( ) = ft
6” round
roof cap 20 ft x ( ) = ft
6” round
roof vent 24 ft x ( ) = ft
Subtotal Column 2 = ft
Subtotal Column 1 = ft
 ft
t

Vent installation should not exceed 100 feet
equivalent length