10 IM 861
Rooftop Installation
1 Before locating the unit on the roof, make sure that the
roof structure is adequate to support the weight involved.
(See Electrical & Physical Tables in this manual.) THIS
IS VERY IMPORTANT AND THE INSTALLER’S
RESPONSIBILITY.
2 For rigging and roofcurb details, see Figures 8, 9, 10 and
11.
3 The location of the unit on the roof should be such as to
provide proper access for inspection and servicing.
IMPORTANT: If unit will not be put into service immediately,
block off supply and return air openings to prevent excessive
condensation.
Ducting
The installing contractor should fabricate ductwork in
accordance with local codes. Use industry manuals as a guide
when sizing and designing the duct system. Contact Air
Conditioning Contractors of America, 1513 16th St. N.W.,
Washington, D.C. 20036.
Place the unit as close to the conditioned space as possible
allowing clearances as indicated. Run ducts as directly as
possible to supply and return outlets. Use of non-flammable
weatherproof flexible connectors on both supply and return
connections at unit to reduce noise transmission is
recommended.
On ductwork exposed to outside temperature and humidity,
use a minimum of 2ⴖ of insulation and a vapor barrier.
Distribution system in attic, furred space or crawl space should
be insulated with at least 2ⴖ of insulation.
1
⁄2ⴖ to 1ⴖ thick
insulation is usually sufficient for ductwork inside the air
conditioned space.
Provide balancing dampers for each branch duct in the supply
system. Properly support ductwork from the structure.
IMPORTANT: In the event that the return air ducts must be run
through an “unconfined” space containing other fuel burning
equipment, it is imperative that the owner must be informed
against future changes in construction which might change this
to a “confined space.” Also, caution the owner against any future
installation of additional equipment (within the existing
unconfined and/or confined space which might create a negative
pressure within the vicinity of other solid, liquid, or gas fueled
units.
Return Air
Figure 8: Flat rooftop installation, attic or drop ceiling
distributing system. Mounted on roofcurb. Curb must be
level.
I299
Never allow products of combustion or the flue products to
enter the return air ductwork, or the circulating air supply. All
return ductwork must be adequately sealed and secured to
the furnace with sheet metal screws, and joints taped. All
other duct joints must be secured with approved
connections and sealed airtight.
Failure to prevent products of combustion from being
circulated into the living space can create potentially
hazardous conditions, including carbon monoxide poisoning
that could result in personal injury or death.
▲▲
DANGER
!
Do not, under any circumstances, connect return ductwork
to any other heat producing device such as fireplace insert,
stove, etc. Unauthorized use of such devices may result in
fire, carbon monoxide poisoning, explosion, personal injury,
property damage or death.
▲▲
DANGER
!
I296
SPREADER BAR
A
B
D
C
LIFTING BEAM
CABLE OR CHAIN
5/8ⴖ SHACKLE
(EACH CORNER)
39ⴖ
26
1
⁄
8
CENTER
OF
GRAVITY
CORNER WEIGHTS BY PERCENTAGE
AB C D
23% 29% 21% 27%
Figure 9: Lifting Detail
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