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Installation
Roof Curb and Ductwork
The roof curbs consist of two main components: a pedestal
to support the unit condenser section and a "full perimeter"
enclosure to support the unit's air handler section.
Before installing any roof curb, verify the following:
•
It is the correct curb for the unit.
•
It includes the necessary gaskets and hardware.
•
The purposed installation location provides the required
clearance for proper operation.
•
The curb is level and square — the top surface of the
curb must be true to assure an adequate curb-to-unit
seal.
Step-by-step curb assembly and installation instructions
ship with each Trane accessory roof curb kit. Follow the
instructions carefully to assure proper fit-up when the unit is
set into place.
Note: To assure proper condensate flow during operation,
the unit (and curb) must be as level as possible. The
maximum slope allowable for rooftop unit
applicationsexcluding SSH_s, is 4" end-to-end and
2" side-to-side. Units with steam coils (SSH_s) must
be set level!
If the unit is elevated, a field constructed catwalk around
the unit is strongly recommended to provide easy access
for unit maintenance and service. Recommendations for
installing the Supply Air and Return Air ductwork joining the
roof curb are included in the curb instruction booklet. Curb
ductwork must be fabricated and installed by the installing
contractor before the unit is set into place.
Note: For sound consideration, cut only the holes in the
roof deck for the ductwork penetrations. Do not cut
out the entire roof deck within the curb perimeter.
Pitch Pocket Location
The location of the main supply power entry is located at
the bottom right-hand corner of the control panel. illustrates
the location for the electrical entrance through the base in
order to enter the control panel. If the power supply conduit
penetrates the building roof beneath this opening, it is
recommended that a pitch pocket be installed before the
unit is placed onto the roof curb.
The center line dimensions shown in the illustration below
indicates the center line of the electrical access hole in the
unit base when it is positioned on the curb, ±3/8 inch. The
actual diameter of the hole in the roof should be at least 1/2
inch larger than the diameter of the conduit penetrating the
roof. This will allow for the clearance variable between the
roof curb rail and the unit base rail illustrated in
p.
28.
28
The pitch pocket dimensions listed are recommended to
enhance the application of roofing pitch after the unit is set
into place. The pitch pocket may need to be shifted as
illustrated to prevent interference with the curb pedestal.
If a Trane Curb Accessory Kit is not used:
•
The ductwork can be attached directly to the factory-
provided flanges around the unit supply and return air
openings. Be sure to use flexible duct connections at
the unit.
•
For "built-up" curbs supplied by others, gaskets must
be installed around the curb perimeter flange and the
supply and return air opening flanges.
•
If a "built-up" curb is provided by others, it should NOT
be made of wood.
•
If a "built-up" curb is provided by others, keep in mind
that these commercial rooftop units do not have base
pans in the condenser section.
•
If this is a REPLACEMENT UNIT without the IRU
option, keep in mind that the CURRENT DESIGN
commercial rooftop units do not have base pans in the
condenser section.
•
Trane roof curbs are recommended. If using a non-
Trane roof curb with right-angle return airflow
approaches to a return fan inlet, a rigid, solid flow baffle
wall should be installed across the full width of the roof
curb return airflow path in the position shown in
17, p. 35
return fan inlet that could contribute to unusual return
fan noise.
•
If a full perimeter curb is used, make sure the IRU
option was added to the unit to ensure stability in the
condenser section
Figure 11. Pitch pocket location
Roof Curb
Cut-a-Way
Figure 11,
to reduce potential airflow disturbances at the
Pedestal
B
C
L
4-13/16"
A
C L
*Control Wire Conduit
Access Area (Illustration Only)
Figure
Conduit Diameter
1/2" Clearance
Pitch Pocket
16" x 8"
RT-SVX072D-EN
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