Dacor DH3606S User Manual

Planning the Installation

Planning the Ductwork

•  To prevent combustion by-products, smoke or odors 

from entering the home and to improve efficiency, tape 

all duct joints securely.

•  Use only ductwork deemed acceptable by state, 

municipal and local codes.

•  Range hoods may interrupt the proper flow of smoke 

and combustion gases from furnaces, gas water heat-

ers and fireplaces. To avoid drawing lethal gases into 

the home, follow the manufacturer’s recommendation 

for these devices and consult NFPA and ASHRAE rec-

ommendations.

•  Failure to install proper ductwork may result in a back 

draft and/or the insufficient venting of smoke and 

fumes.

•

do not install an additional in-line or external blower 

to increase the length of the duct run. Even small dif-

ferences between blower air flow rates can greatly 

reduce the air draw by the hood.

•

cAution - 

To reduce the risk of fire and to properly 

exhaust air, be sure to duct air outside the house or 

building. Do not vent exhaust air into spaces within 

walls or ceilings or into attics, crawl spaces or garages.

•  For optimal performance, consult a qualified HVAC 

specialist when designing the duct system.

•  All ductwork materials (including screws and duct tape) 

must be purchased separately by the customer. When 

planning new ductwork, always look for the shortest, 

most direct route to the outside. 

•  The exhaust connects to 8-inch dia. round duct. You 

may increase the duct size over the duct run if desired. 

To prevent a back draft, never decrease the duct size 

over the run. If existing ductwork is smaller than 8 inch-

es, remove and replace with 8-inch ductwork.

•  Do not rely on tape alone to seal duct joints. Fasten all 

connections with sheet metal screws and tape all joints 

with certified silver tape or duct tape. Use sheet metal 

screws as required to support the duct weight.

•  To prevent back-drafts, a damper at the duct outlet may  

be required. Make sure ductwork does not interfere 

with floor joists or wall studs.

Calculating the Maximum Duct Run Length

The maximum straight duct length for the hood is deter-

mined by the type of duct used. See the chart below.

8” round

60 feet

10” round

50 feet

3¼” X 10” rectangular

50 feet

For each elbow and transition added to the ductwork, a cer-

tain number of feet must be subtracted from the maximum 

duct run to compensate for wind resistance. To determine 

the length the ductwork cannot exceed, subtract all of 

the equivalent lengths of the elbows and transitions listed 

below from the maximum duct run above.

Ductwork Equivalent Lengths

8” 90° elbow

7 feet

10” 90° elbow

5 feet

8” 45° elbow

3 feet

10” 45° elbow

2 feet

3¼” X 10”

to round 90° 

transition

25 feet

3¼” X 10” to

8”/10” round tran-

sition

4 feet

3¼” X 10” 

90° elbow

15 feet

3¼” X 10” 

90° flat elbow

20 feet

3¼” X 10” 

45° elbow

7 feet

Roof cap or wall 

cap with damper

*

* The equivalent lengths of roof and wall caps vary with 

model and configuration. For equivalent length, contact the 

manufacturer or a qualified HVAC specialist.

Ductwork Design Tips

Wherever possible, reduce the number of transitions and 

turns to as few sharp angles as possible. Two staggered 

45° angles are better than one 90°.
Keep turns as far away from the hood exhaust as possible, 

and as much space between bends as possible.
For best performance, use round duct instead of rectangu-

lar, especially when elbows are required.
If multiple elbows are used, try to keep a minimum of 24 

inches straight duct between them.
Avoid “S” or “back to back” use of adjacent elbows.
In regions where the weather gets extremely cold, use ther-

mal breaks, such as a short section of non-metallic duct, to 

avoid indoor heat loss. Locate the break as close as pos-

sible to the outside pass through point.
Do not use flexible metal duct.
Do not use ductwork that is smaller in cross-sectional area 

than the recommended types above.

fan

fan

elbow (not 

included)