4.4A Fresh Air/Supply Air
CAUTION!
DO NOT draw air directly from the kitchen, laundry, or isolated
basement.
You may draw air from a basement that is open to the home. All
flexible ducting connected to the UA-90H should be UL listed.
A short piece of flexible ducting on all UA-90H duct connections
is recommended to reduce noise and vibration transmitted to
rigid ductwork in the structure. Ducting the UA-90H as mentioned
requires consideration of the following points:
Duct Sizing: For total duct lengths up to 25’, use a minimum 10"
diameter round or equivalent rectangular. For longer lengths, use a
minimum 12" diameter or equivalent. Grills or diffusers on the duct
ends must not excessively restrict airflow.
Isolated Areas:
Effective
dehumidification may require that ducting be branched to isolated,
stagnant air flow areas. Use 8" or larger diameter branch ducting
to each of two or three areas, use 6" or larger to each of four or
more areas. Provisions must be made to provide airflow from
supply locations to central return location. Proper air distribution
is important to ensure even humidity control and heat distribution
throughout the structure. See Figure 1.
Connecting to existing HVAC systems:
An optional 10" check
backdraft damper is available to prevent reverse air flow through
the UA-90H. If the UA-90H is ducted to the supply of an air handler,
the check damper should be placed in the UA-90H supply duct.
Ventilation operation is controlled by the remote controls offered
with the UA-90H. These controls determine the time/frequency
that the unit introduces outside air. The amount of outside air can
be restricted by the blade damper in the 6" collar. Some control
options require a 6" motorized damper be installed in the 6" fresh
air duct.
CAUTION!
Contact the factory when connecting to a static pressure of
greater than or equal to +.5" WG.
4.4B Ducting for Fresh Air — Option
Fresh air may be brought into the structure by connecting an
insulated duct from outside the structure to the 6" inlet of the UA-
90H. Advantages of this form of ventilation include:
1. Outside air is filtered before entering the building.
2. Outside air will be dehumidified before entering if the UA-90H
is running in dehumidification mode.
3. Drawing air from outside and blowing inside aids in slightly
pressurizing the structure. This helps prevent dirty and humid
air from entering elsewhere. It also reduces the potential for
carcinogenic radon gas to enter and provides a small amount
of make-up air for open combustion and exhaust devices like
the clothes drier, fireplace, and water heater.
4. Exhaust fans are recommended in the bath rooms and
kitchen.
In cold climates or areas where the outdoor dew point is low at
times, ventilation can be used to dehumidify the structure, making
the UA-90H capable of year-round drying. This is accomplished
by bringing the dry, low dew point air into the structure during
these times. This approach is often more economical than running
the dehumidifier to remove excess moisture from the structure.
In cold climates, it is critical to adequately ventilate to reduce the
inside moisture content to avoid moisture accumulating in the wall
cavities. For example; in a house that experiences condensation on
the interior surface of the windows during the winter, increasing the
amount of ventilation will often cure the problem.
An insulated 6" diameter duct is generally sufficient to provide up
to 75 CFM of outside air. Large quantities of outside air will impact
UA-90H performance positively or negatively, depending upon the
inside and outside air conditions.
The outside air duct should be connected to the 6" round collar on
the front of the unit. The amount of outside air can be restricted
by the blade damper in the 6" collar. These controls determine
the time/frequency that the unit introduces outside air. The
amount/frequency of ventilation should be based on the size and
occupancy of the residence. If you are unsure of your ventilation air
requirements or have need for higher air flows, consult the factory
by calling 1-800-533-7533 for assistance.
FOR HVAC INSTALLER ONLY
7
Ultra-Aire 90H Installer’s & Owner’s Manual
