i
nstallation
C
onsiderations
IM 1059-12 LARGE VERTICAL WSHP
9
www.DaikinApplied.com
Ductwork and attenuation
Discharge ductwork is normally used with these
conditioners. Return air ductwork may also be required
but will require field installation of a return air duct collar.
All ductwork should conform to industry standards of
good practice as described in ASHRAE Systems Guide.
The discharge duct system will normally consist of a flexible
connector, a transition piece to the final duct size, a short
run of duct, an elbow without vanes and a trunk duct tee’d
into branch ducts with discharge diffusers. Transformation
duct must not have angles totalling more than 30 degrees
or severe loss of air performance can result.
All units have multiple fan outlets. The preferred method
for minimum static pressure loss would be individual
ducts at each outlet connected to a larger main duct
downstream (
Figure 9
).
For minimum noise transmission, the metal duct material
should be internally lined with acoustic fibrous insulation.
The ductwork should be laid out so that there is no line
of sight between the conditioner discharge and the
distribution diffusers.
Return air ducts can be brought in adjacent to the return
air of the conditioner. Typically, the equipment room
becomes the common return air plenum.
Do not insert sheet metal screws directly into the unit
cabinet for connection of supply or return air ductwork,
especially return air ductwork which can hit the drain pan
or the air coil.
Ventilation air
Outside air may be required for ventilation. The
temperature of the ventilation air must be controlled so
that mixture of outside air and return air entering the
conditioner does not exceed conditioner application limits.
It is also general practice to close off the ventilation air
system during unoccupied periods (night setback).
The ventilation air system is generally a separate
building subsystem with distribution ductwork. Simple
introduction of the outside air into each return air plenum
chamber reasonably close to the conditioner air inlet
is not only adequate, but recommended. Do not duct
outside air directly to the conditioner inlet. Provide
sufficient distance for thorough mixing of outside and
return air.
Notes:
1. Transformations to supply duct have maxi-
mum slope of 1" to 7".
2. Square elbows with double thickness vanes
may be substituted.
3. Do not install ducts so that the air flow is
counter to fan rotation. If necessary, turn fan
deck assembly and motor.
4. Transformations and units shall be adequate-
ly supported so no weight is on the flexible
connection.
Figure 9: Suggested supply ducting per ASHRAE and SMACNA publications
Flexible
Connector
Flexible
Connector
Flexible
Connector
Note 2
Note 2
Note 2
Note 1
Note 1
Note 1
Fan Rotation
(See Note 3)
Transformation Duct
Flexible Connector
Main Duct
Branch Duct
Trunk Duct
Distribution
Diffuser
Note 2
Fan Rotation
(See Note 3)
Fan Rotation
(See Note 3)
Fan Rotation
(See Note 3)
