[Equest-users] Fwd: no heating loads to systems --part II

[Pasha Korber-Gonzalez]

Thank you both for looking at this.  I'm a bit dumbfounded that it can't be
as easy as the fact that I need to specify reheat, since I have indicated
that it is a VAV with reheat system, but if that is the case then I will
re-instate the reheat delta t so that I can generate heating energy.   (when
I had input a reheat delta t of 30 degrees F, I was able to successfully fun
a simulation, but the heating energy numbers where so high (i.e. 30 kWH/sq
ft or more) that it just didn't seem like this was the correct input for my
model.

I just think that it is a bit weird even for the programming that the only
way I can get heat out of the heating coil is that I have to enlist reheat
or baseboards in order for the system to assume that there is a heating
load.

I understand the logic of why this works, but I don't understand why it is a
requirement in DOE to have some or ll of the heating capacity specified for
it to "autosize" or react to the fact that heating loads need to be passed
to the systems module only if reheat or baseboards are specified.

If it is possible for any of the eQuest programmers to comment on this input
requirement I would like to hear thier feedback.  In the meantime, what I am
understanding is that it is a requirement to specify supplementary heating
(i.e reheat or baseboards)  in DOE2 for a VAV reaheat system before DOE2
will allow a basic heating coil to assume a heating load...somebody please
tell me I'm wrong-because this doesn't make sense.

Pasha

---------- Forwarded message ----------
From: Seun Odukomaiya <sodukomaiya at laceindy.com>
Date: Sat, Mar 6, 2010 at 4:59 PM
Subject: RE: [Equest-users] no heating loads to systems --part II
To: Pasha Korber-Gonzalez <pasha.pkconsulting at gmail.com>


 Pasha,
I took a look at your model. When employing a VAV-Reheat System as you have
in your model, you must also specify the reheat Delta-T for the zone heating
coils attached to the units (see attached screenshot). If this is not done,
the program assumes that the zones have no reheat, and thus will never put a
load on your hot water loop. This, in turn, causes the error that you've
seen. The DOE-2 documentation describes it as follows:



Maximum increase in temperature for supply air passing through the zone (or
subzone) reheat coils. The value specified here applies to all zones in the
system. This keyword is required in order to simulate heating the air as it
passes through the terminal reheat coil. Note that when very little air is
passed (see MIN-FLOW-RATIO) there may be insufficient reheating.



According to your model, the maximum zone entering supply air temperature is
105 degrees. I also noticed that your zone minimum entering supply
temperature is 55 degrees. As such, you need to specify your reheat delta-T
as 50 degrees (as in the screenshot). This ensures that your zone coils are
able to raise the 55-degree air from the AHU up to the 105 degrees that you
have specified. Try that, and your model should run just fine.



*Seun Odukomaiya, LEED AP  -  **Mechanical Engineer*

L'Acquis Consulting Engineers

9229 Delegates Row, Suite 550

Indianapolis, Indiana 46240

voice:  (317) 706-2075, ext. 255

fax:     (317) 706-2076

email:  sodukomaiya at laceindy.com

web: www.laceindy.com

P* **Please consider the environment before printing this e-mail.*

 ------------------------------
*From:* equest-users-bounces at lists.onebuilding.org [
equest-users-bounces at lists.onebuilding.org] On Behalf Of Pasha
Korber-Gonzalez [pasha.pkconsulting at gmail.com]
*Sent:* Saturday, March 06, 2010 4:26 PM

*To:* eQUEST Users List
*Subject:* [Equest-users] no heating loads to systems --part II

   Hi all,

okay-I'm back to where I was last time I posted this question:  why are
there no heating loads being passed to my systems?

Here's the story: (160,000 sf high school building)

The attached file is my baseline 90.1 model using System 7 (VAV w/reheat)
As the file is now-I have removed the reheat delt-T (30 deg), and removed
any baseboard heating in all /systems/zones and removed any input of heating
capacity of the coils.  With this, my file receives the following error:
***ERROR***********************************************************************

Loop: Hot Water Loop has zero design flow.

Check input for consistency, or specify design loads.
Right now I am trying to have DOE2 'autosize' anything it can so that I can
get a good run and go back and adjust equipment capacities....but I don't
know where else I can look further for why the systems aren't receiving the
design loads.---thus creating the above error.  Something is stopping DOE
from passing the loads to the systems.  When I open my sim file, the only
reports being produced are the L-reports.

If anyone has any hints or can take a look to find what it is I'm missing--I
know it's a simple thing, but can't seem to find why it is doing this.
(I've been staring at these files tooo long...)

---on a side note--after all the help I received with this issue earlier
this week I have input all of the temp schedules that are required, and all
that I know needs to be input to get the systems to run.  any help would be
greatly appreciated so I don't have to go back and rebuild this model from
the beginning....I'm too close to the end to go back and rebuild
another file.

Thanks in advance!
Pasha
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