[bldg-sim] Another DOE-2 question..

Aulbach, John JAulbach at semprasolutions.com
Thu Aug 7 14:48:49 PDT 2003

Jason - My previous question had to do with the apparent small difference in
Return Air and Mixed Air Temperature in hourly printout from a DOE-2.1E
model. I also asked if the input of Outside Air at the ZONE level translated
into the SYSTEM level.

I received several kind suggestions to insure I had my OUTSIDE-AIR-CFM set
correctly, as well as:

No, OA is done as PO being <>0 thus Tmix being Trx(1-PO) + Toa*PO.
Is OA-CONTROL fixed?  Does SV-A show the system OA fraction as what you
expected; if not, you may
have used the wrong keyword.

Jeff Hirsch
James J. Hirsch & Associates
Building Performance Analysis Software & Consulting
12185 Presilla Road
Camarillo, CA 93012-9243 USA
phone: (805) 553-9000
fax: (805) 532-2401
email: Jeff.Hirsch at DOE2.com
web: http://DOE2.com
Graham & Megan [hamnmegs at ozemail.com.au]

Outside air set at zone level should be fine and takes precedence over any
system level outdoor air command.  
Have you checked variable #39 (PO) to see if the outdoor air damper is in
fact open?  If not then have you set outdoor air requirements using
OA-CHANGES or CFM/person?  if the latter then you need to have people in the
space to have outside air delivered - i.e. works like demand controlled
Aside from that what you suggest should work.  You may want to look at
ambient and return air humidity ratio as well so you can see you latent
ventilation load ...
(John again)

As it turned out, I DID have my OUTSIDE-AIR-CFM in ZONE set ridiculously low
(BLUSH). When I correct the OSA back to the Design numbers, the T mix and T
Return became much further apart. So, indeed, the ZONE level OSA DID
translate into the SYSTEM level. And reasonable numbers ensued.

Thanks again to ALL who helped me square this away !!!

John R. Aulbach, PE, CEM
Project Engineer
Sempra Energy Solutions
555 West Fifth Street
Mail Location 27F3
Los Angeles, CA 90013
Tel: (213) 244-8551 Cell (213) 219-4875

"Sempra Energy Solutions is not the same company as SDG&E/ SoCalGas, the
Utilities.  Sempra Energy Solutions is not regulated by the California
Public Utilities Commission, and you do not have to buy Sempra Energy
Solutions products or services to continue to receive quality regulated
service from the Utilities."  

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