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18
Connecting Fresh Air Duct
The indoor ceiling cassettes have a fresh air intake port for ventilation. A booster fan and
duct (field supplied) must be used to feed outdoor air to the indoor unit.
Determine the duct diameter, length and booster fan size based on the required airflow.
See table below for duct and hole sizes:
NOTE: Fresh air intake amount should be 10% or less of whole air amount to
prevent condensation.
Unit Size Hole Diameter
Duct Diameter
(BtuH) inch (mm) inch (mm)
24,000 4.4 (113) 2.9 (73)
To install fresh air intake:
1. Locate and remove the pre-punched knockouts hole for ventilation duct on ceiling cassette unit.
Do not remove the knockout and open the hole at this point.
2. Remove the factory installed insulation on the outside of ceiling cassette where the pre-punched
knockout was located.
3. Install field supplied ductwork. Recommended ductwork is either an insulated flex duct, or
insulated sheet metal duct suitable for working temperatures up to 140° F (60° C).
4. Use a field-supplied power ventilation fan to increase airflow to meet job requirements.
Follow the manufacturer's installation instructions provided with the power ventilation kit.
5. Install a field supplied air filter to prevent dust and dirt from entering the ceiling cassette unit
and fouling indoor coil.
6. Install a field supplied mechanical duct damper to close during shutdown periods.
7. All metal ductwork should be covered with insulation to prevent condensation forming.
Fresh air hole
Fresh air hole
FRESH AIR INTAKE (24K Size Only)
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