Therma-Stor Products Group 90H - Manual (Page 6)

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.
4.4C Installation in a Basement or Crawlspace with an
Existing Forced Air HVAC System.
Basement Installation: Install a separate 10" return for the UA-
90H in a central area of the structure. Optional: Duct the supply
of the Ultra-Aire to a 10" x 10" x 10" tee/damper, adjusted to
20% open to the basement. Duct the other side of the tee to the
air supply of the existing HVAC system with a backdraft damper.
Connect a duct from outside to the 6" collar of the Ultra-Aire if you
wish to provide ventilation air. See Figure 2.
Crawlspace Installation: Install a separate return for the UA-90H
in a central area of the structure. Optional: Duct the supply of the
UA-90H to a 10" x 10" x 10" tee/damper that is 20% open to
the crawlspace if desired. Duct the other side of the tee to the
air supply of the existing HVAC system with a backdraft damper.
Connect an insulated duct from outside to the 6" collar of the UA-
90H if you wish to provide optional ventilation air.
Instead of installing a separate return to the UA-90H, and if the
existing system has multiple returns, it is possible to select one to
disconnect from the existing forced air system and use it for the
dedicated Ultra-Aire 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, alternatively, install a separate
return from the open part of the house.
4.4D Installation in an Attic with an Existing Forced Air
HVAC System
CAUTION!
ALWAYS install a catch pan with a drain or float interrupt
for condensate under the UA-90H in an attic or condensate
may damage the living space below.
The interrupt switch should be installed in series with the field wire
that connects the blue (#5) lead from the UA-90H to the blue (#5)
lead on the control panel. If overflow occurs, this switch opens
the compressor control circuit and stops water production before
the catch pan overflows. The UA-90H will continue to ventilate or
circulate air as normal, but will not dehumidify until this switch
closes.
The preferred method of installation is to create a separate return
for the UA-90H in a central area of the structure. Duct the supply of
the UA-90H to the air supply of the existing HVAC system. Connect
an insulated duct from outside to the 6" collar of the UA-90H if you
wish to provide fresh make-up air. Adjust a damper in the duct to
provide the desired.
4.4E Installation in a Structure with No Existing Forced
Air HVAC System
When installing the UA-90H in a structure that does not have a
forced air HVAC system, a single return for the UA-90H should
be installed in central open area of the structure. DO NOT locate
the return in a bathroom or a kitchen. The supplies of the UA-
90H should be located in the remote areas of the structure (such
FOR HVAC INSTALLER ONLY
6 Ultra-Aire 90H Installer’s & Owner’s Manual 7 Ultra-Aire 90H Installer’s & Owner’s Manual