C Ducting For Fresh Air; D Installation In A Basement Or Crawlspace With An Existing Forced Air Hvac System - Ultra-Aire SD12 Installer's & Owner's Manual

FOR HVAC INSTALLER ONLY

3.9C Ducting for Fresh Air

Fresh air can be brought into the structure by connecting an
insulated duct from outside to the 6" Ultra-Aire SD12 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
the remote control to bring in fresh air. Refer to Section 7.8B 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 and cooled before entering if the
Ultra-Aire SD12 is running in dehumidification mode.
3. Drawing air from outside and blowing inside aids in slightly pres-
surizing 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 combus-
tion 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 economi-
cal 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 con-
densation 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 100 CFM of outside air. Large quantities of outside air will either
positively or negatively impact the performance of the Ultra-Aire
SD12, depending upon inside and outside air conditions. Consult
the factory by calling 1-800-533-7533 for recommendations re-
garding 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 or check your local building
codes.
3.9D Installation in a Basement or Crawlspace with an
Existing Forced Air HVAC System
It is recommended that a new, separate return duct be installed
for the Ultra-Aire SD12 from a central area of the house. If this is not
possible, and if the existing system has multiple returns, select one
to disconnect from the existing forced air system and use it for the
dedicated Ultra-Aire SD12 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.
If the structure in which the Ultra-Aire SD12 is to be installed has an ex-
isting forced air HVAC system, utilize the HVAC system ducting to make
the Ultra-Aire SD12 installation easier.
Basement Installation: Install a separate 10" return for the Ultra-Aire
SD12 in a central area of the structure. Duct the supply of the Ultra-Aire
SD12 to an optional 10" x 10" x 10" tee/damper that is 20% open to the
basement. This allows the dehumidifier to discharge a variable amount
of dehumidified air into a basement that may not be well served by the
existing duct system. Duct the other side of the tee to the air supply of
the existing HVAC system. A backdraft damper is required in the duct
between the 10" tee and the central supply duct to prevent air from be-
ing discharged into the basement during central fan operation. Connect
a duct from outside to the 6" collar of the Ultra-Aire SD12 if you wish to
provide fresh air ventilation.
Crawl Space Installation: Install a separate return for the Ultra-Aire
SD12 in a central area of the structure. Duct the supply of the Ultra-
Aire SD12 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 ventilation. Connect an insulated duct from
outside to the 6" collar of the Ultra-Aire SD12 if you wish to provide
optional fresh air.
FIGURE 14A: DEHUMIDIFIER BASEMENT INSTALL
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Ultra-Aire SD12 Installer's & Owner's Manual