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8. Check
for
gas
leaks
factory- -installed gas lines after all piping connections have
been completed. Use a commercially available soap solution
(or method specified by local codes and/or regulations).
Step 9 — Install Duct Connections
The unit has duct flanges on the supply- - and return- -air openings
on the side and bottom of the unit. For downshot applications, the
ductwork connects to the roof curb (See Fig. 3 and 4 for
connection sizes and locations).
Configuring Units for Downflow (Vertical) Discharge
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal
injury or death.
Before installing or servicing system, always turn off main
power to system and install lockout tag. There may be
more than one disconnect switch.
1. Open all electrical disconnects before starting any service
work.
2. Remove horizontal (metal) duct covers to access vertical
(downflow) discharge duct knockouts in unit basepan. (See
Fig. 9.)
CAUTION
!
PROPERTY DAMAGE HAZARD
Failure to follow this caution may result in property damage.
Collect ALL screws that were removed. Do not leave screws
on rooftop as permanent damage to the roof may occur.
3. For single- -phase models only, on the discharge side only,
remove the insulation covering the downshot (plastic)
knockout. Insulation is held in place with aluminum tape.
Please note that large chassis units have 2 pieces of insula-
tion, and only the piece over the downshot knockout needs
to be removed. Discard insulation.
4. To remove the downshot (plastic) knockouts for both sup-
ply and returns, break front and right side connecting tabs
with a screwdriver and hammer. Push cover down to break
rear and left side tabs. These plastic knockouts are held in
place with tabs similar to an electrical knockout. Discard
plastic knockout covers.
5. Set unit on roof curb.
6. Verify that the downshot ducts are aligned with the down-
shot knockout areas.
7. Re- -install horizontal (metal) covers as needed to seal unit.
Ensure openings are air and watertight.
NOTE: The design and installation of the duct system must be in
accordance with the standards of the NFPA for installation of
nonresidence- -type air conditioning and ventilating systems, NFPA
90A or residence- -type, NFPA 90B; and/or local codes and
ordinances.
at
the
field- -installed
and
Horizontal Duct Covers
Basepan
Downflow
(Vertical)
Supply
Knockout
Fig. 9 - - Supply and Return Duct Opening
Adhere to the following criteria when selecting, sizing, and
installing the duct system:
1. Units are shipped for horizontal duct installation (by
removing duct covers).
2. Select and size ductwork, supply- -air registers, and
return- -air grilles according to American Society of Heating,
Refrigeration and Air Conditioning Engineers (ASHRAE)
recommendations.
3. Use flexible transition between rigid ductwork and unit to
prevent transmission of vibration. The transition may be
screwed or bolted to duct flanges. Use suitable gaskets to
ensure weather- -tight and airtight seal.
4. All units must have field- -supplied filters or accessory filter
rack installed in the return- -air side of the unit.
Recommended sizes for filters are shown in Table 1.
5. Size all ductwork for maximum required airflow (either
heating or cooling) for unit being installed. Avoid abrupt
duct size increases or decreases or performance may be
affected.
6. Adequately insulate and weatherproof all ductwork located
outdoors. Insulate ducts passing through unconditioned
space, and use vapor barrier in accordance with latest issue
of Sheet Metal and Air Conditioning Contractors National
Association (SMACNA) and Air Conditioning Contractors
of America (ACCA) minimum installation standards for
heating and air conditioning systems. Secure all ducts to
building structure.
7. Flash, weatherproof, and vibration isolate all openings in
building structure in accordance with local codes and good
building practices.
10
A09061
Basepan
Downflow
(Vertical)
Return
Knockout
A09088
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