How do I model a Dedicated Outdoor Air System (DOAS)?

When modeling this type of system for Nonresidential buildings the approach will vary depending upon the type of Calculation.

  1.  For the DOE-2 calculation (used in the 90.1 calculation, nonresidential performance calcs), you put in a dummy zone for the DOAS.  This dummy zone can be conditioned zones in the building.
  2. For the CBECC Com calculation (used for Nonresidential T24 Performance calcs) you do not need a dummy zone.  See our example, DOAS.bld.  Note that currently, this calculation only permits a DOAS systems feeding Zonal Type Systems (Four Pipe Fan Coil, Packaged Terminal Air Conditioners and Heat Pumps, Hydronic Heat Pumps, SplitDX , PackagedDX, Single Packaged Vertical Units and VRFs). Simply create your System level of the tree, then select the “Outside Air From” setting on the main tab.

Note that for Multifamily files, the DOAS approach is not recognized.  IAQ fans for this purpose are input at the Zone level of the Building Tree, Dwelling Units tab.

Categories: 8. Nonresidential Mechanical

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