Thermador HMWB30, HMWB36 installation manual Ventilator performance calculation

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

Fl exible ducting:

If flexible metal ducting is used, all the equivalent feet values in the table should be doubled. The flexible metal duct should 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
				x 10 "	9 ft.
		3-1/4"
			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