Hey Brian,

Attached are some select conversations I've been involved in the past
few years on this list - they cover a range of topics regarding how to
handle DOA systems - recommended reading if you have the time/patience.

As you may have gathered, there are a few ways to skin the cat when it
comes to DOAS in equest. You can boil them all down to two basic
approaches...

Whether you need a dummy/space zone depends on whether you will be
modeling the system as a separate entity. If you'll read the attached,
you'll find I'm generally an advocate of not doing that, but whether
this is the way to go is ultimately a gut-check and dependant on the
behavior of the proposed systems you're trying to model:

1. Start by determining exactly when how your DOAS's fans, ERV
components, and separate pre-conditioning/defrost components (if any),
operate. Determine whether these things operate in sync with any served
HVAC equipment or independently.

2. If the DOAS's fans and other components operate on largely the
same schedule as the associated other HVAC equipment, I would say to
ignore the dummy zone concept and instead "split" the DOAS into each
associated unit (see attached discussion and more in the archives).

3. If the DOAS operates under a largely different schedule, or you
if you can't be sure, then I'd suggest pursuing modeling the system
independently, assigned to a dummy zone (again, read up further on tips
regarding dummy zones and how to use OA-FROM-SYSTEM). If DCV is
involved anywhere (CO2 sensors), be especially careful to understand how
that plays into your actual system, and read up on how exactly to deal
with that before getting started.

Hopefully that gets you and others started... do use the list archives,
and ask specific questions if you hit any deadends.

It may comfort/discomfort you to know that there's probably more than
one right answer out there ;).

~Nick

NICK CATON, E.I.T.