GE 39-40425 Installation Instructions, Exhaust connection, Maximum duct length, Total Ductwork

Installation Instructions

NOTE: If you need to install ducts, note that the total duct length of 31⁄4″ x 10″ rectangular or 6″ diameter round duct should not exceed 140 equivalent feet. Outside ventilation requires a HOOD EXHAUST DUCT. Read the following carefully.

NOTE: It is important that venting be installed using the most direct route and with as few elbows as possible. This ensures clear venting of exhaust and helps prevent blockages. Also, make sure dampers swing freely and nothing is blocking the ducts.

Exhaust connection:

The hood exhaust has been designed to mate with a standard 31⁄4″ x 10″ rectangular duct.

If a round duct is required, a rectangular-to-round

transition adaptor must be used. Do not use less than a 6″ diameter duct.

Maximum duct length:

For satisfactory air movement, the total duct length of

31⁄4″ x 10″ rectangular or 6″ diameter round duct should not exceed 140 equivalent feet.

Elbows, transitions, wall and roof caps, etc., present additional resistance to airflow and are equivalent to a section of straight duct which is longer than their actual physical size. When calculating the total duct length, add the equivalent lengths of all transitions and adaptors plus the length of all straight duct sections. The chart below shows you how to calculate total equivalent ductwork length using the approximate feet of equivalent length of some typical ducts.

	EQUIVALENT		NUMBER		EQUIVALENT
DUCT PIECES	LENGTH	x	USED	=	LENGTH

Rectangular-to-Round	5 Ft.	x	(	)	=	Ft.
Transition Adaptor*
Wall Cap	40 Ft.	x	(	)	=	Ft.
90° Elbow	10 Ft.	x	(	)	=	Ft.
45° Elbow	5 Ft.	x	(	)	=	Ft.
90° Elbow	25 Ft.	x	(	)	=	Ft.
45° Elbow	5 Ft.	x	(	)	=	Ft.
Roof Cap	24 Ft.	x	(	)	=	Ft.
Straight Duct 6″ Round or	1 Ft.	x	(	)	=	Ft.
31⁄4″ x 10″ Rectangular

Total Ductwork =

Ft.

*IMPORTANT: If a rectangular-to-round transition adaptor is used, the bottom corners of the damper will have to be cut to fit, using the tin snips, in order to allow free movement of the damper.

Equivalent lengths of duct pieces are based on actual tests and reflect requirements for good venting performance with any vent hood.

5