[bldg-sim] Makeup Air using OA-FROM-SYSTEM in equest/doe2

[Nicholas Gayeski]

Hi all,

This list is a great help, thanks to everyone who contributes.

I am trying to model a building in equest/doe2 with Fan Coil units in each 
zone and a make up air system supplying minimum outdoor air.  My problem is 
that the fan power and cooling loads seem too high while the heating loads 
seem too low.  I'm not sure why but I suspect it has to do with the set up 
of the MUA units and the OA-FROM-SYSTEM command.  I have seen a few of the 
posts describing how to set up MUA using OA-FROM-SYSTEM, but it's still not 
clear to me.  Can anyone clarify?

Here is what I've done:

1.  Zones with Fan Coil systems have OA supplied by MUA units using 
OA-FROM-SYSTEM.
2.  Zone OA specified by OA/person and/or OA/ft^2
3.  A dummy space and zone was set up for the MUA units.
4.  MUA units have supply/return flow specified as designed.
5.  MUA units have min-oa-method as fraction of design flow = 1
6.  MUA units have oa-sizing by sum of zone oa (does this conflict with 
specifying design flows?)
7.  MUA units have neutral max and min supply temperatures

Here are some of my suspicions...

1.  I am letting doe2 size the fancoils - could that cause problems?
2.  Some zones have multiple fan coil units as designed, but I am assuming I 
can group those zones and let doe2 size one fan coil units to meet the 
loads.
3.  Do I need to specify total supply/return flows per zone instead of 
oa/person or oa/ft^2?
4.  Does the OA-FROM-SYSTEM command automatically return zone air through 
the MAU, or do I need to specify exhaust flow?  I am assuming supply=return 
automatically.
5.  One last thing, can I have multiple zones under a MAU or just the dummy 
zone?  e.g. if I want to control the MAU supply temperature using the a zone 
(corridors) rather than neutral temperatures...

Thanks for the help,

Nick Gayeski
Building Technology Program, MIT

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