3.4C Ducting for Fresh Air
Fresh air can be brought into the structure by connecting a insulated
duct from outside to the 6” UA-150H inlet and by turning on the
fan switch or activating the humidity control (on units with the
humidity control panel). Activate the ventilation timer on units with
the ventilating & humidity control panel to bring in fresh air. Refer
to section 4.5 for programming instructions for the ventilation timer.
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-150H
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 make-up air for
open combustion and exhaust devices like the clothes drier,
fireplace, and water heater.
4. Adequate 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.
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 125 CFM of outside air. Large quantities of outside air will impact
UA-150H performance positively or negatively, depending upon
the inside and outside air conditions. Consult the factory by calling
1-800-533-7533 for recommendations regarding the use of higher
flows with your specific application.
The outside air duct should be connected to the 6” round collar on
the filter enclosure of the unit. The 6” round collar includes a manual
damper. Adjust the manual damper to provide the desired amount of
fresh air for ventilation. The amount of fresh air should be based on
the size and occupancy of the residence. If you are unsure of your
ventilation air requirements, consult the factory by calling 1-800-
533-7533 for assistance.
3.4D Installation in a Basement or Crawlspace
with an Existing Forced Air HVAC System
If the existing system has multiple returns, select one to disconnect
from the existing forced air system and use it for the dedicated
UA-150 return. Always select a return from a central location in the
structure in an area that is always open to the rest of the structure.
Do not use a return from a room that may have its’ door closed
much of the time or install a separate return from the open part of
the house.
If the structure in which the UA-150 is to be installed has an existing
forced air HVAC system, utilize the HVAC system to make the UA-150
installation easier.
Basement Installation: Install a separate 10” return for the UA-150H
in a central area of the structure. Duct the supply of the UA-150 to
a 10” x 10” x 10” tee/damper that is 20% open to the basement.
Duct the other side of the tee to the air supply of the existing HVAC
system. Connect a duct from outside to the 6” collar of the UA-150
if you wish to provide fresh make-up air.
Crawl Space Installation: Install a separate return for the UA-150H in
a central area of the structure. Duct the supply of the UA-150H to a
10” x 10” x 10” tee/damper that is 20% open to the crawl space if
desired. Duct the other side of the tee to the air supply of the existing
HVAC system. Connect an insulated duct from outside to the 6” collar
of the UA-150H if you wish to provide optional fresh make-up air.
FOR HVAC INSTALLER ONLY
6
Ultra-Aire 150H Installer’s & Owner’s Manual
