Thermador HPWB30, HPWB48, HPWB36 Ventilator performance calculation, Flexible ducting

Table 1. Ventilator performance calculation

Us e this chart to compute maximum permissable lengths for duct runs to outdoors .

Note: Do not exceed maximum permissable equivalent lengths!

Maximum recommended duct length for these hoods: 150 feet

Flexible ducting:

If flexible metal ducting is used, all the equivalent f eet values in the table should be doubled. The flexible metal duct shou ld be straight and smooth and extended as much as possible.

Do NOT use flexible plastic ducting.

Note: Any home ventilation system, such as a

gas furnaces, gas water heaters and other naturally vented systems. To minimize the chance of interruption of such naturally vented systems, follow the heating equipment manufacturer’s guidelines and safety standards such as those published by NFPA and ASHRAE.

*Hoods are supplied with a 10" round transition. A locally supplied transition is required for other sizes.

Note: Outlet on top of hood is 8-1/8" x 8".

Duct Piece

10" round
to 8" roun d		5 ft.
Round ,		1 ft.
straight		(per foot
		length)
3-1/4" x 10"		1 ft.
3-1/4" x 12 "		(p er f oot
straight		length)
		8" Di a. 17 ft.
90° elbow		10" Dia. 24 ft .
		8" Di a. 10 ft.
45° elbow		10" Dia. 14 ft .
3 -1⁄4" x 12"		15 ft.
3-1/4" x 10"		14 ft.
90° elbow
3-1/4"	x 10 "	8 ft.
3-1/4"	x 12 "	9 ft.
45° elbow
3-1/4" x 10"		33 ft.
3-1/4" x 12"		36 ft.
90° flat elbow
10"round transition
to 3-1/4" x 10" or
3-1/ 4" x 12"		9 ft.
3-1/4" x 10" or
3-1/4"	x 12" to
10" round transiti on		6 ft.
10" round to 3-1/4" x 10"		16 ft.
3-1/4"	x 12" transition	13 ft.
90° elbow
3-1/4"	x 10 "	9 ft.
3-1/4" x 12" t o 10" round		8 ft.
transiti on 90° elbow
Roun d		8" Dia. 32 ft.
wall cap		10" Dia. 41 ft.
with damper
3-1/4" x 10"		24 ft.
3-1/4"	x 12" wall cap	26 ft.
with damper
Round		8" Dia. 44 ft.
roof cap		10" Di a. 56 ft .

Total Duct Run

7