[Equest-users] DOAS and system HP

[Jeff Ross-Bain]

Dear eQuest Experts,

I have a nagging issue that I hope someone can clarify. It has to do with DOAS units and fan motor HP.

We have a DOAS unit that supplies all outside air (OA) to a battery of WSHP units. In preparing the model, I used the "dummy zone" approach, conditioned the air, and all of that air is then the source of OA to the WSHPs. By the way, in this system, a portion of the return air from the WSHPs enters the DOAS.

The question is how is the actual DOAS unit HP modeled? This unit is 20HP supply and 7.5HP return (exhaust). The dummy zone HP auto sized is much less than the actual. However, if I input actual (i.e. kW/cfm), the energy use soars.
Am I missing something? I wonder if the size of the dummy zone matters, or if some of the fan power is included in the WSHP and exhaust systems...

Thanks,

Jeff Ross-Bain, BEMP, LEED Fellow
President
404-220-8955
www.rbgb.com<http://www.rbgb.com/>

Build Green. Save Time. Save Money.



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