BUILDING VENTILATION DESIGN GUIDE
Method 5: Decoupled Dedicated Outdoor Air System (DDOAS)
Provide a separate, dedicated outdoor-air system designed to filter, condition, and dehumidify ventilation air and deliver it directly to the
conditioned space through a separate register or grille. This approach requires a separate independent ventilation duct system not
associated with the Multi F system.
Advantages
• Does not add additional heating or cooling loads to indoor units.
• May be used with the full lineup of Multi F indoor units.
• Failure of outdoor unit does not impact operation of indoor unit, the
resulting untreated air will be readily noticed by the occupants.
• The outdoor air unit may supply “neutral” air to the occupant space
even when the Multi F indoor unit fan changes speed or cycles on
and off. DDOAS controls do not have to be interlocked with the
Multi V F system.
• In lieu of installing localized smaller outside air treatment
equipment throughout the building, this method centralizes the
ventilation air source making service and filter changes easier and
less disruptive for the building occupants.
• Third-party demand control ventilation controls are more readily
accommodated.
• Indoor unit operation and performance will not be affected by the
condition of outdoor air.
Disadvantages
• Ceiling space is required to accommodate ductwork between the
outdoor air unit and ceiling diffusers.
LG recommends using the DDOAS method in all installations.
Outdoor
Air Unit
Indoor Unit s
Ceiling Diffuser
Indoor Unit
Figure 43: Decoupled Dedicated Outdoor Air System (DDOAS).
Due to our policy of continuous product innovation, some specications may change without notication.
©LG Electronics U.S.A., Inc., Englewood Cliffs, NJ. All rights reserved. “LG” is a registered trademark of LG Corp.
352 | APPLICATION GUIDELINES
Multi F and Multi F MAX Indoor Unit Engineering Manual
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