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Step 5 — Select and Install Ductwork
The design and installation of the duct system must be in
accordance with the standards of the NFPA for installation of
non--residence type air conditioning and ventilating systems,
NFPA 90A or residence--type, NFPA 90B and/or local codes and
ordinances.
Select and size ductwork, supply -- air registers, and return air grilles
according to ASHRAE (American Society of Heating,
Refrigeration, and Air Conditioning Engineers) recommendations.
The unit has duct flanges on the supply-- and return -- air openings
on the side of the unit.
PERSONAL INJURY HAZARD
Failure to follow this warning could result in personal
injury or death.
For vertical supply and return units, tools or parts could
drop into ductwork Install a 90 degree turn in the return
ductwork between the unit and the conditioned space. If a
90 degree elbow cannot be installed, then a grille of
sufficient strength and density should be installed to
prevent objects from falling into the conditioned space.
Units with electric heaters require 90 degree elbow in
supply duct.
!
WARNING
When designing and installing ductwork, consider the following:
1. All units should 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.
2. Avoid abrupt duct size increases and reductions. Abrupt
change in duct size adversely affects air performance.
IMPORTANT: Use flexible connectors between ductwork and
unit to prevent transmission of vibration. Use suitable gaskets to
ensure weather tight and airtight seal. When electric heat is
installed, use fireproof canvas (or similar heat resistant material)
connector between ductwork and unit discharge connection. If
flexible duct is used, insert a sheet metal sleeve inside duct. Heat
resistant duct connector (or sheet metal sleeve) must extend 24--in.
(610 mm) from electric heater element.
3. Size ductwork for cooling air quantity (cfm). The minimum
air quantity for proper electric heater operation is listed in
Table 2. Heater limit switches may trip at air quantities
below those recommended.
4. Seal, insulate, and weatherproof all external ductwork. Seal,
insulate and cover with a vapor barrier all ductwork passing
through conditioned spaces. Follow latest Sheet Metal and
Air Conditioning Contractors National Association
(SMACNA) and Air Conditioning Contractors Association
(ACCA) minimum installation standards for residential
heating and air conditioning systems.
5. Secure all ducts to building structure. Flash, weatherproof,
and vibration-- isolate duct openings in wall or roof
according to good construction practices.
CONFIGURING UNITS FOR DOWNFLOW
(VERTICAL)
DISCHARGE
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal
injury or death.
Before performing service or maintenance operations on the
system, turn off main power to unit and install lockout tag.
There may be more than one disconnect switch.
!
WARNING
1. Open all electrical disconnects and install lockout tag before
starting any service work.
2. Remove horizontal (metal) ductcovers to access vertical
(downflow) discharge duct knockouts in unit basepan. (See
Fig. 6.)
3. To remove downflow return and supply knockout covers,
break front and right side connecting tabs with a
screwdriver and hammer. Push cover down to break rear
and left side tabs.
Horizontal Duct Covers
A09076
Basepan
Downflow
(Vertical)
Supply
Knockout
Basepan
Downflow
(Vertical)
Return
Knockout
A09093
Fig. 6 -- Supply and Return Duct Opening
NOTE: These panels are held i n place with tabs similar to an
electrical knockout. Reinstall horizontal duct covers (Fig. 6)
shipped on unit from factory. Insure 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.
Adhere to the following criteria when selecting, sizing, and
installing the duct system:
1. Units are shipped for side shot installation.
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
50VT--A