[Equest-users] DOAS results

Wed Oct 20 09:35:09 PDT 2010

Brian, this interesting. What about the humidity properties? Does the
DOAS pass on the Return air humidity level, too? Can you tell me where
the explanation about the DOAS return air being assigned to terminal air
OSA input is located in the eQuest literature? It might hint at the
humidity conditions. 

Kathryn Kerns

Systems Specialist

BCE Engineers, Inc.

| Ph: 253.922.0446 | Fx: 253.922.0896 | 

________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Brian
Fountain
Sent: Wednesday, October 20, 2010 9:23 AM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] DOAS results

Remember that eQUEST doesn't really do DOAS yet.  All it does is set the
OA temperature for the borrowing zone using the OA-FROM keyword to the
RA temperature of the "lending" system (which is why it has to come
first on the system list). 

I really hope this changes in future releases! 

On 10/19/2010 7:25 PM, Carol Gardner wrote: 

Are you willing to share your .inp and .pd2 input decks? I would take a
quick look if you are.

Carol

On Tue, Oct 19, 2010 at 12:40 PM, Fleming, Joe <joe.fleming at tlc-eng.com>
wrote:

I know this topic has been beaten like..., but the results I have been
getting for the ## hours on a model with several DOAS's are horrible,
(getting a little delirious at this point).  There is a DOAS for each
system with a different schedule than the next.  Each DOAS has an ERV
which operates with a DH of 2.0btuh/hr in cool/heat and float.  

I feel like the problem is within the dummy zone or the schedules.  

When I assign the DOAS air to the SZRH unit as OA from System the
cooling load shoots up by about 50%, (even when I remove the ERV the
results are similar, increased cooling).  

The building is in a moderate climate zone.

The DOAS fan schedule is set to on at the same time as the SZRH unit.

The heating energy is reduced when I assign the DOAS.

The problems I see are, to list a few;

The dummy zone has all of its hours outside of the throttling range no
matter how it is assigned and no matter what the t-stat schedule I
assign.

The load doesn't budge once I remove the DOAS from the model, only when
I add it to the SZRH unit as OA from system.

The DOAS does not show any heating load, only cooling load all year long
(again moderate climate with cold seasons).

DOAS's have been done before without this problem, maybe adding too much
info this time.

*How is the DOAS operating in eQuest?

Taking a stab I assume it is bringing in the OA and cooling it or
heating it to whatever the temperature set-points are.  Depending on the
schedules the temp could be floating most of the time.  The air is then
brought into your secondary system at set-point or floating point.  The
OA from the zones attached to the secondary system are replaced by the
OA from the DOAS. (?)  Then the secondary system does its thing as
usual.   

(Not sure what is happening with the dummy zone?  Does DZ care it gets
any air?  Looks like it does because of the unmet hours.  Does the
secondary system pick up the air from the DOAS after it has traveled
through a space and picked up load?  The dummy zone has no load but it's
temp is always above 85.)

Now for the cooling to be increasing, the air must be coming in to the
secondary system warmer than usual during cooling hours.  (usual being
the raw temperature of uncond outdoor air).   But the results seem
extreme.

For the heating to be decreasing the air must be coming in warmer than
usual for the secondary system, which it is based on SS-O.

Does anyone have experience with this and what could be going wrong?   

*Or, can someone link me to a basic DOAS goby?  

I have searched the archives but many of the DOAS questions have gone
unanswered in the past.

Thank You

Joe Fleming

E.I., LEED AP BD+C, BEMP

Mechanical Engineer I

TLC Engineering for Architecture
Your 2030 Challenge Partner

800 Fairway Drive, Suite 250

Deerfield Beach, FL 33441-1816

phone: 

954-418-9096

fax: 

954-418-9296

direct: 

954-418-4591

website: 

www.tlc-engineers.com

  <http://www.tlc-engineers.com/> 

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