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

[Bishop, Bill]

Pasha,
 
For VAV systems you also have to specify the HEAT-SET-T (Hot Deck Max
Leaving Temp) to enable the main air handler heating coil. You can't
just leave the field blank. For example, if your room supply air
temperature is 90F and you have 30F reheat, enter 60F for the hot deck
temp.
 
Regards,
Bill
 
William Bishop, EIT, LEED(r) AP | Pathfinder Engineers & Architects LLP
Mechanical Engineer
 
134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005
wbishop at pathfinder-ea.com
www.pathfinder-ea.com
P Please strive to live sustainably.         
________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Pasha
Korber-Gonzalez
Sent: Monday, March 08, 2010 10:30 AM
To: John Aulbach
Cc: eQUEST Users List
Subject: Re: [Equest-users] Fwd: no heating loads to systems --part II
 
Thanks John/Vik- Yes. but when I do put in reheat that is the only way
the systems are receiving reheat, so my question is why are the heating
coils not doing the primary heating wherefore in my case file, all of
the heating is up to either reheat (specified by me) or via baseboards
(also specified by me.)   
 
The big question is:  why aren't the heating coils doing the job first,
and then the excess is to be made up via reheat and/or baseboards.
 
I have not specified any input for humidty control (based on the help
file recommendations--b/c we don't have humidification control in the
proposed building...
 
The DOE2 help file indicates:

REHEAT-DELTA-T

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.
The highlighted statement is noted, but it still doesn't indicate that
this input is required in order to simulate any heating requirement.  It
only states it is required to simulate reheat heating requirements.  Why
don't the heating coils work in my model is my "black & white"
question....  all in all my space heating energy (with reheat &
baseboards) is only 1% of the total building energy for a climate in
Vancouver, BC...  why is it so low?
 
...if I am just really missing something---please don't hesitate to tell
me so. ---- I have also specified the hot deck temp coming off the htg
coils which then gave me some capacity in my heating coils, but
unfortunately by adding this input  all of my numbers have dropped
instead of increased.
 
I also looked back into the archives to find an answer to this issue--I
found two others who were having the same problems I have, but they have
responded that they never figured out the problem either...
 
Pasha
 
 
On Sat, Mar 6, 2010 at 10:34 PM, John Aulbach <jra_sac at yahoo.com> wrote:
Pasha:
 
I believe the short answer to this is that not all VAV zones have
reheat. Therefore, you need to put reheat in the zones that have it.
otherwise, all systems would get reheat.
 
John Aulbach
 
________________________________

From: Pasha Korber-Gonzalez <pasha.pkconsulting at gmail.com>
To: eQUEST Users List <equest-users at lists.onebuilding.org>; Vikram Sami
<vsami at lasarchitect.com>
Sent: Sat, March 6, 2010 9:30:09 PM
Subject: [Equest-users] Fwd: no heating loads to systems --part II
 
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 <http://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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