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Caution must to be used when not using the flexible duct,
the air velocity from the drilled outlet may create noise. Drilled
Outlets CANNOT be installed in a residential structure; too much
noise may be generated from the outlets. In commercial areas
with large ceilings the sound can be absorbed by the room or is
not a concern because of the ambient noises.
Drilled outlets are commonly used to supply a large area with
heating and cooling. Drilled outlets can also be used to create
a pressurized air curtain for bay doors, or large openings to the
outside environment. When drilled outlets are used with the
Hi-Velocity System a few points to remember:
•
When multiple 1
1
/4” (32mm) or 2” (51mm) holes are used,
they need to be a minimum of 6” (152mm) apart on center
(Fig. 37).
• One 1
1/4” (32mm) drilled hole is equivalent to a single 2”x10’
AFD kit (2”/51mm Rough-In Boot attached to a 10’/3.05m
piece of flex duct). With the 11/4” (32mm) drilled outlet the
throw from the outlet is up to 18’ (5.49m).
•
One 2” (51mm) drilled outlet is equivalent to two - 2”x10’ AFD
kits (2”/51mm Rough-In Boot attached to a 10’/3.05m piece
of flex duct). With the 2” (51mm) drilled outlet the throw from
the outlet is up to 30’ (9.14m) in distance.
•
Using drilled outlets larger than 2” (51mm) is not
recommended; with too large of an opening in the main
plenum the static pressure may drop to an unacceptable
level.
Fig. DUC-37 - 6” (152mm) Apart on center
When drilled outlets are used in a ceiling install, drill the outlets
at a 45° angle to properly circulate the room air (Fig. DUC-38).
Plenum Runs on Ceiling
Fig. DUC-38 - Airflow 45° angle to floor
Fig. DUC-39 - 6” (152mm) Airflow parallel to floor
If there is an air velocity noise coming from the drilled outlets,
a static pressure reading from the plenum duct should be taken.
This reading is to be taken no closer than 18” (457mm) from supply
air outlet of fan coil. Static pressure readings are taken from the
inside edge of the plenum; do not insert pitot tube deeper than
1/4”(6.7mm) from the inside surface of the plenum.
If the static pressure is high, drilling more holes into the main
plenum will lower the static pressure and the noise level of the
system. The standard supply pressures for the Hi-Velocity System
runs between 0.7”H
2
O (174 pa) and 1.2”H
2
O (299 pa). Do not
allow the static pressure to drop below 0.7”
H
2
O
(174 pa) as this
can cause a low airflow.
For sidewall installations the outlets are drilled parallel to the
floor (Horizontal airflow). When the vents are in this configuration,
they can be used to create a pressurized air curtain.
Plenum Runs on Sidewall
Drilled Outlets
Module DUC
Installing Plenum and Branch Duct (9/9)
Module DUC Installing Plenum and Branch Duct (9/9)
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