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DUCTWORK
For houses without ducted heating or cooling systems (Fig.2):
In most houses one or two fresh air grilles in a central part of the house provide effective distribution of the fresh air into the home, particularly when the
stale exhaust air is picked up at several points. Because the fresh air is usually somewhat cooler than the indoor air, the fresh air supply grilles should
be located in a high traffic area like a hallway or stairway rather than in a sitting area. If you want to get fresh air into specific room with high occupancy,
you can split up the fresh air supply.
For houses with forced-air heating and cooling systems (Fig.1 Fig.3 Fig.4):
Most units are installed with the fresh air duct connected directly to a return duct for the main heating and cooling system.
Be careful to connect the fresh air duct at least three feet from the return plenum to minimize suction from the furnace blower. A connection closer to
the furnace may result in unbalanced flow or other associated problems.
For installations that collect stale air from specifc rooms in the home (Fig.1 Fig.2):
Locate stale air return grilles (RA) in rooms where moisture and odors are generated: bathrooms, the kitchen, and perhaps areas where contaminants
may be generated such as the home workshop. Return grilles in these areas such as the home workshop may be dampered so that they can be shut
off when not in use. A central location such as a hallway is also acceptable, but it won't clear humidity and odors from baths and kitchens quickly.
Locate stale air return grilles (RA) near the ceiling on inside walls. Stale air returns are usually easiest to install in interior partitions.
EXHAUST & OUTSIDE AIR DUCTS
The EA Duct and the OA Duct connect the unit to the outside. Flexible insulated duct is usually used.
Exhaust Air & Outside Air (EA & OA)
Fresh Air & Stale Air (FA & RA)
All ducts from unit to house in unconditioned spaces like attics and crawl spaces MUST BE INSULATED.
WARNING
DO NOT PLACE ANY STALE AIR RETURNS IN GARAGES.
INSTALLING OUTSIDE AIR & EXHAUST AIR DUCTS
Ducts connecting the unit to the outside must be well- insulated. Vapor barrier is required on both inside and outside of the insulation. The inlets and
outlets should be screened against insects and vermin and shielded from the weather to prevent the entry of rain or snow.
CAUTION
a1. The vapor barrier should be continuous and sealed against air and moisture leakage! If not, condensation or ice may form in cold
weather on the duct surface or in its insulation!
a2. INSTALL FRESH AIR INLET AWAY FROM SOURCES OF CONTAMINANTS
• Do not locate the fresh air inlet where vehicles may be serviced or left idling.
• The fresh air inlet should be at least ten feet away from any exhaust such as dryer vents, chimneys, furnace, and water heater
exhausts or other sources of contamination or carbon monoxide.
• Never locate the fresh air inlet inside a structure
INSTALLING RETURN AIR (RA) DUCTS
All the stale air returns are connected by ducts to the unit. Generally, empty stud cavities are used for returns as is often done with cold air returns for
the furnace, using standard duct boots to connect to six inch pipe at the bottom or top of the wall cavity. Always be sure to seal all joints with duct
sealant or tape. Some local codes may require metal ducting all the way from the boots to the stale air grilles. Rigid ducts will allow the air to move freely
and easily through the ducts.
Do not use more flex duct than necessary!
Flex duct is much more resistant to airflow than rigid duct; longer runs of flex duct will reduce the ventilation performance of your system. Stretch flex
duct and avoid sharp bends.
CAUTION
• Do not connect Dryers directly to the unit.
• Do not connect Range Hoods to the unit.
NOTE: Seal all duct collars at unit to minimize air leakage.
WARNING
DANGER OF ELECTRICAL SHOCK WHEN SERVICING THE UNIT.
ALWAYS UNPLUG UNIT BEFORE CONNECTING OR SERVICING CONTROLS.
Stale Air Return Grille Sizes
Bathroom
4" X 10" or 6" X 10" - 40 to 60 sq. in.
Kitchen
6" X 10" or 60 sq. in.
Duct Minimum Sizes and Type
6" round insulated duct
6" round un-insulated duct
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