Air DistributionSystem
For airflow data (blower performance data, blower speed
tap settings, etc.) see the Parts List.
Ductwork
NOTE: The total heat gain!heat loss from the structure as
expressed in total Btu/hr MUST be calculated by manufac-
turer's method or in accordance with "A.S.H.R.A.E. Guide"
or "Manual J - Load Calculations" published by the Air
Conditioning Contractors of America or in Canada"H.R.A.I.
Residential Heating and Cooling Load Calculation Manual."
The total heat qain calculated should be equal to or less
than the cooling capacity output based on D.O,E. test
procedures, steady state efficiency times input.
Ductwork, supply registers, and return air grilles MUST be
designed and sized to handle the unit's cooling air vol-
ume requirements. If the unit is connected to an existing
system, the ductwork MUST be checked to make sure it is
adequate. Extra runs or larger duct sizes may have to be
installed.
Maximum recommended velocity in trunk ducts is 1000 feet
per minute (5.08m/s). Velocity in branches should not ex-
ceed 800 feet per minute (4.06m/s). Refer to the Parts List
for unit air volume requirements and system sizing recom-
mendations.
NOTE: Ductwork sizing affects temperature rise and cool-
ing temperature differential. Be sure to properly size
ductwork to the capacity and airflow characteristics of your
unit. Failure to do so can affect limit controls, compressors,
motors, and other components and will lead to premature
failure of components. This will also adversely affect dayto
day unit performance.
Refer to unit rating plate for proper Electric Heat Accessory
sizing and see the Temperature Rise Check section in the
Electric Heat Accessory Installation Instructions.
Ductwork Insulation
It is recommended that ductwork installed outdoors have a
minimum of 2" (51mm) of fiberglass insulation and be cov-
ered by a weatherproof vapor barrier that is protected
against damage. Caulking and flashings, or other means
adequate to provide a permanent weather seal, must be
used.
It is recommended that ductwork installed in attics or other
areas exposed to outdoor temperatures have a minimum of
2" (51mm) fiberglass insulation and have an indoor type va-
por barrier.
Ductwork Connections
The use of flexible, non-combustible connectors between
main trunk ducts and supply and return air plenums is rec-
ommended to minimize vibration transmission.
NOTE: Connect supply and return air plenums to unit in a
manner that will allow the top of the unit to be removed with-
out removing plenums. Plenums MUST be individually
sealed to unit casing. Ducts MUST be terminated inside
structure.
Filters
All return air MUST pass through a filter before entering the
unit. An electronic air cleaner, optional filter racks or other
accessible filter arrangements MUST be installed in the re-
turn air ductwork. Minimum recommended filter areas are
based on a velocity of 300 ft/min (1.2m/s) for disposable fil-
ters and 500 ft/min (2.54m/s) for washable high velocity
filters.
CAUTION
Do NOT operate the unit without all filters in place.
81 51601 110200
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