Dacor MH30 - Manual (Page 9)

7
Planning the Installation
wArning
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 ceil-
ings or into attics, crawl spaces or garages.
To prevent combustion by-products, smoke or odors
•
from entering the home and to improve efficiency,
tape all duct joints securely.
Use only duct work constructed of materials deemed
•
acceptable by state, municipal and local codes.
Range hoods may interrupt the proper flow of smoke
•
and combustion gases from furnaces, gas water
heaters and fireplaces. To avoid drawing lethal gases
into the home, follow the manufacturer’s recom-
mendation for these devices and consult NFPA and
ASHRAE recommendations.
Failure to install a remote blower or proper duct work
•
may result in a back draft and/or the insufficient vent-
ing of smoke and fumes.
do not
• install an additional in-line or external blow-
er to increase the length of the duct run. Even small
differences between blower air flow rates can greatly
reduce the air draw by the hood.
All duct work materials (including screws and duct tape) •
must be purchased separately by the customer. When
planning new duct work, always look for the shortest,
most direct route to the outside. The blower assembly
can be rotated to accommodate venting (and wiring)
through the top A or the back B .
The hood exhaust connects to an 8-inch round duct. •
You can 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 duct work is smaller
than 8 inches in diameter, remove it and replace it with
8-inch duct work.
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 require to support the duct weight.
To prevent back-drafts, a damper at the duct outlet may
•
also be required.
Make sure duct work does not interfere with floor joists
•
or wall studs.
On dual exhaust models, the two 8” exhausts may be
•
merged into one 10” duct using Dacor transition kit
AHT10. See page 16 for details.
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.
duct siZe MAXiMuM duct run
8” round 60 feet
10” round 50 feet
3¼” X 10” rectangular 50 feet
For each elbow and transition added to the duct work, a
certain number of feet must be subtracted from the maxi-
mum duct run to compensate for wind resistance. To deter-
mine the length the duct work cannot exceed, subtract all of
the equivalent lengths of the elbows and transitions listed
below from the maximum duct run above.
Duct Work Equivalent Lengths
eQuivAlent lengths
piece subtract piece subtract
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
transition
4 feet
Roof cap *
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.
Duct Work 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”
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 duct work that is smaller in cross-sectional area
than the recommended types above.
A
B