Honeywell DH90A1007 Installation Guide - Page 5

For HVAC Installer Only • Installation Guide 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 throughout the structure. 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 DH90. 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 DH90 is running in dehumidification mode. 3. Drawing air from outside and blowing inside aids in slightly pressurizing the Figure 2: Basement or crawlspace installation. structure. This helps prevent dirty and humid air from entering elsewhere. Exhaust fans are recommended in the bathrooms and kitchen. An insulated 6" diameter duct is generally sufficient to provide up to 75 CFM of outside air. Large quantities of outside air will impact DH90 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 side of the unit. The amount of outside air can be restricted by the blade damper in the 6" collar. The actual amount of ventilation air being delivered through the ventilation ducts must be measured in each installation. Refer to the instructions provided with the W8150 Ventilation Control for proper setup instructions. 4.4C Installation in a Basement or Crawl Space with an Existing Forced Air HVAC System Install a separate 10" return for the DH90 in a central area of the structure. Optional: Duct the supply of the DH90 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 DH90 if you wish to provide ventilation air. See Figure 2. Indoor air return W8150 Controller Heating A/C return air Heating A/C supply air Fresh air Inlet hood EARD6 motorized damper Dry air to basement