Bosch DHD Model User Manual
Page 8
DUCTWORK INSTALLATION GUIDE-
LINES
● Ducting should vent directly outdoors
(not into an attic, underneath the house,
into the garage or into any enclosed
space). A Recirculation Module is availa-
ble when ducting to the outside is not
possible.
● Keep duct runs as short and straight as
possible.
● Duct fittings (elbows and transitions)
reduce air flow efficiency.
● Back to back elbows and ”S” turns give
very poor delivery and are not recom-
mended.
● A short straight length of duct at the inlet
of the remote blower gives the best deli-
very.
● Transition to duct from the integral blo-
wer or remote duct transition as close to
the downdraft as is possible. In order of
preference, use
1st. 10” round duct
2nd. 8” round duct
3rd. 3-1/4” x 14” duct
4th. 7” round duct
5th. 3 -1/4” x 10” duct
6th. 6” round duct
● The use of flexible metal round duct
should only be used when no other duct
fitting exists. Limit use to short lengths
and do not crush when making corners.
● Back to back elbows should be avoided.
DUCTWORK INSTALLATION
GUIDELINES
● Where local codes permit, plastic pipe
(PVC-schedule 40 pipe or ABS pipe 7”
or 8” diameter) can be used in areas of
high ground moisture and in slab floors
to eliminate future rusting.
● Use only duct work constructed of mate-
rials that are acceptable by the applica-
ble codes. All duct should be 26 gauge
or heavier to minimize flex due to air
flow.
● The remote blowers require a 10” or 6”
diameter round duct (depending on
model) to match the inlet ring. A transiti-
on is necessary from other duct sizes.
● Use sheet metal screws as required to
support the duct weight, and seal all
joints with duct tape.
● Be certain that the duct work does not
interfere with floor joists or wall studs.
● Do not exhaust more than one vent into
a single duct run.
● Cold weather installations should have
an additional backdraft damper installed
to minimize backward cold air flow and a
nonmetallic thermal break to minimize
conduction of outside temperatures as
part of the ductwork. The damper
should be on the cold air side of the
thermal break. The break should be as
close as possible to where the ducting
enters the heated portion of the house.
● Always use an appropriate roof or wall-
cap with damper. Laundry type wall caps
should never be used.
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