Dr. Kat,

You are correct. I'm not sure how far into the rabbit hole you feel
like going, but let me add a couple additional points:

1) What you choose for "System per Area" in the Air-Side Wizard (Screen
1) will determine whether eQUEST creates one plenum per zone or one
plenum per floor. Selecting "System per Zone" results in one plenum
zone for each occupied zone (in addition to the system being replicated
for each specified zone, of course), and any of the other three options
result in one plenum per floor. This has implications for modifying
building geometry in the detailed interface in addition to return air
temperatures.

2) The difference between an unconditioned zone a plenum zone, as far as
eQUEST is concerned, is whether or not the zone is a return air path for
its parent system (assuming non-ducted return). Both are considered
unconditioned space types. So, for example, you could have a mechanical
room as a zone, specify it as a plenum, and its parent system will
consider that zone's temperature when determining the return air
temperature. Plenums do not necessarily have to be above-ceiling.

3) If you choose ducted return in the wizard, eQUEST will turn your
above-ceiling "plenum" into an unconditioned zone.

4) An unconditioned zone cannot have exhaust specified, but exhaust flow
and fan power, as well as a make-up air source, can be specified for a
plenum zone.

Thanks,

Dakota Kelley