Therma-Stor Products Group 90H owner manual 4B Ducting for Fresh Air Option

FOR HVAC INSTALLER ONLY

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 from the factory 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.

IMPORTANT

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.

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.

6 Ultra-Aire 90H Installer’s & Owner’s Manual