weird autosizing / return air path problems

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I'm getting some weird results from the current eQuest 3.64 model I'm

14 story office building, parallel FP terminals (using PIU system).
Plenums have been modeled, although usually I leave them out.

Two things are happening:

1) If I let eQuest autosize the systems, the fan CFM are
outrageous. On the order of 10 CFM per sq ft. If I put in a design CFM
(closer to 1 CFM per sq ft), the results are more consistent with what I
expect, but there are no unmet load hours either. So why the heck is
eQuest oversizing the fan systems?

2) I can't "force" the return air path to be anything other than
"Plenum Zones". Even if I change it to duct or direct, after running
eQuest, I go back in to the model and the system I changed has reverted
back to plenum zones.

Has anyone ever seen this issue before?

Unfortunately I can't send out inp and pd2 files, sorry!

James Hansen, PE, LEED AP

James Hansen's picture
Joined: 2011-09-30
Reputation: 200

1. no idea

2. Check to see if the "plenum zones" are labeled as unconditioned or plenum
int he zone pages. if it is plenum then they have to be used in the
calculation as a plenum return system. if you change them all to
unconditioned, they will be labeled as "plenum zones" but will allow you to
call out direct or duct return systems.


rdh4176's picture
Joined: 2011-02-14
Reputation: 0