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JOHNSON CONTROLS
5276178-JIM-C-0118
If the unit is equipped with both a building pressure
transducer and a duct static transducer, a “tee” will
be factory installed, and both the duct static pressure
transducer and building pressure will be connected to
the “tee” - both building static pressure transducer and
duct static transducer will use the same factory supplied
atmospheric pressure probe.
The “low” side connection of the
duct static or building pressure trans
-
ducers are shipped with the pneumatic
tubing factory installed and routed, to
the external factory pressure tap.
ROOF CURB INSTALLATION
General Information
When ordered, the roof curb is shipped knocked-down
in a separate container and needs to be field assembled
and installed.
Refer to Installation Manual that is
shipped with the roof curb for specific instructions.
The roof curb drawings contained in the Johnson
Controls literature are not intended as construction
documents for the field fabrication of a roof curb.
Johnson Controls will not be responsible for the unit fit
up, leak integrity, or sound level with field fabricated
roof curbs. Construction documents for field fabricated
roof curbs are available upon request.
Wood or Fiber Cant Strips, Roofing
Felts, Roofing Material, Caulking and
Curb-To-Roof Fasteners are to be field
supplied.
DUCT SYSTEM
Duct Connection Guidelines
Ductwork should be designed and sized according
to the methods in Manual Q of the Air Conditioning
Contractors of America (ACCA).
All intake and discharge air duct connection to the
unit may be made directly to the unit. These air duct
connections should be on flexible material and should
be installed so they are sufficiently loose. Duct runs
and transitions must be made carefully to hold friction
loss to a minimum. Avoid short turns, and duct elbows
should contain splitters or turning vanes.
Duct work connected to the fan discharge should run in a
straight line for at least
two
equivalent outlet diameters.
Never deadhead the discharge into the flat surface of
a plenum.
A closed return duct system should be used. This will not
preclude use of economizers or outdoor fresh air intake.
The supply and return air duct connections at the unit
should be made with flexible joints to minimize noise.
When the unit is equipped with power exhaust fans or
return air fan the return duct should have a 90 elbow
before opening to the building space to abate noise.
The supply and return air duct systems should be
designed for the CFM and static pressure requirements
of the job. They should NOT be sized to match the
dimensions of the duct connections on the unit.
If the unit is equipped with hot water or steam heat then
the supply air direction will be down only.
Installation of elbows, discharge
damper and other abrupt flow area
changes installed directly at the fan
outlet will cause system losses. These
losses must be taken into account
during the design phase and must be
added to any field measurements.
SOUND AND VIBRATION TRANSMISSION
All roof mounted air handling units generate some
sound and vibration that may or may not require some
special treatment of the air conditioned space. The noise
generated by the air handling unit is dependent on the
speed of the fan, the amount of air the fan is moving,
the fan type and the static efficiency of the fan. In
applications where sound and vibration transmissions
may be objectionable, good acoustical engineering
practices must be incorporated in the system design.
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