IM 738-2
23
Mechanical Installation:
Roof Curb Assembly and Installation
Roof Curb Assembly and Installation
Locate the roof curb and unit on a portion of the roof that can
support the weight of the unit. The unit must be supported to
prevent bending or twisting of the machine.
If building construction allows sound and vibration into the
occupied space,
locate the unit over a non-critical area. It is
the responsibility of the system designer to make adequate
provisions for noise and vibration in the occupied space.
Install the curb and unit level to allow the condensate drain to
flow properly and allow service access doors to open and close
without binding.
Integral supply and return air duct flanges are provided with
the RPS/RFS roof curb, allowing connection of duct work to
the curb before the unit is set. The gasketed top surface of the
duct flanges seals against the unit when it is set on the curb.
These flanges must not support the total weight of the duct
work. See “Installing Ductwork” on page 49 for details on duct
connections. It is critical that the condensate drain side of the
unit be no higher than the opposite side.
Assembly of a typical RPS/RDT roof curb is shown in
Figure 29 on page 24. Parts A through K are common to all
units having bottom return openings. Depending on the unit
length, Parts L and M may be included with the roof curb kit to
create the correct overall curb length. Figure 28 shows the
assembly of the RCS roof curb.
RPS/RDT Assembly instructions (Figure 29 on
page 24)
1
Set curbing parts A through K per dimensions shown over
roof opening or on a level surface. Note location of return
and supply air openings.
2
If applicable, set other curbing parts (D, L, M, etc.) in place
making sure that the orientation complies with the
assembly instructions. Check alignment of all mating bolt
holes. See Detail A.
3
Bolt curbing parts together using fasteners provided.
Tighten all bolts finger tight.
4
Square entire curbing assembly and securely tighten all
bolts.
5
Position curb assembly over roof openings. Curb must be
level from side to side and over its length. Check that top
surface of the curb is flat with no bowing or sagging.
6
Weld curbing in place. Caulk all seams watertight. Remove
backing from 0.25" (6 mm) thick × 1.50" (38 mm) wide
gasketing and apply to surfaces shown by cross-hatching.
7
Flash curbing into roof as shown in Detail B.
8
Parts E and F are not required on units with no return shaft
within the curb perimeter.
9
Parts G and H are not required on units with no supply shaft
within the curb perimeter.
10
Be sure that electrical connections are coordinated (see
Figure 30).
RCS Assembly instructions (Figure 28)
1
Set curbing parts (A) in place making sure that the
orientation complies with the assembly instructions. Check
alignment of all mating bolt holes.
2
Bolt curbing parts together using fasteners provided.
3
Curb must be level from side to side and over its length.
4
Weld curbing in place. Caulk all seams watertight and
insulate between channels.
5
Flash curbing into roof as shown in Detail C.
Figure 28. RCS roof curb assembly
WARNING
Mold can cause personal injury. Some materials such as
gypsum wall board can promote mold growth when damp.
Such materials must be protected from moisture that can enter
units during maintenance or normal operation.
B
A
4
4
. U n i t B a s e
. G a l v a n i z e d u r b
. G a l v a n i z e d u i r b o v e r
4 . x 4 N a i l e r S t r i p
. R i g i d I n s u l a t i o n ( n o t f u r n i s h e d )
6 . a n t S t r i p ( n o t f u r n i s h e d )
. F l a s h i n g ( n o t f u r n i s h e d )
8 . u r b G a s k e t i n g
9 . I n s u l a t i o n b e t w e e n
G a l v a n i z e d u r b ( n o t f u r n i s h e d )
0 . R o o f i n g M a t e r i a l ( n o t f u r n i s h e d )
8
0
9
6
D e t a i
6 "
A
A
6 "
" Z Z "
6 "
6 "
A
B
RCS unit size
ZZ
in.
mm
015C–030C
31.0
787
036C & 040C
94.0
2057
045C–060C
62.0
1575
070C–105C
100.0
2540
115C–135C
120.0
3048
Summary of Contents for RDT-135c
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