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

[Pasha Korber-Gonzalez]

sorry all- somehow the last file got corrupt-wrong zones/systems, etc...

please don't use that file.

pk

On Mon, Mar 8, 2010 at 8:29 AM, Pasha Korber-Gonzalez <
pasha.pkconsulting at gmail.com> wrote:

> 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
>>
>> 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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