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

[Charles Land]

Try taking your heat control off scheduled and try coldest to compliment your warmest setting on cooling.  Also you may need to enter a capacity for your heating coils in order to get them to enable.  Ive had this problem in the past, but considering you have 50 degree reheat in your zones this shouldn't be the problem.  I would guess it's the schedule setting, Im not sure what schedule that looks at but im pretty sure taking that out should fix your problem.

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 12:01 PM
To: Bishop, Bill
Cc: eQUEST Users List
Subject: Re: [Equest-users] Fwd: no heating loads to systems --part II

Thanks Bill,

I do have specified 105 supply temp, 105 hot deck max temp, 50F reheat delta T.  For some reason my results are very low for my ASHRAE baseline building & they are showing virtually 1% heating energy consumption overall in my building, and I have one standard effeicency boiler in the plant side.

This is what I know (by gut feel) the issue is--somewhere in the airside I have either turned on or off some control or schedule--along with when I set up the model using the wizard initial inputs they were for the proposed case (water-to-water heat pumps-geothermal htg/clg & serving all spaces including thermal displacement vent, natural vent zones (for htg baseboards), FC's etc.  So----I am wondering if when I saved my file for the baseline model and then switched the plant equip (chiller/boiler) & VAV sys if there is a carry-over input from the HPsystems (or other) that is affecting the lack of heating energy with the standard systems.

Not sure how to find a 'carry-over' input.  I have compared my input files with examdiff program and couldn't find anything specific.

I've attached the non-corrupted files to this email...

pk
On Mon, Mar 8, 2010 at 8:54 AM, Bishop, Bill <wbishop at pathfinder-ea.com<mailto:wbishop at pathfinder-ea.com>> wrote:
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
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wbishop at pathfinder-ea.com<mailto:wbishop at pathfinder-ea.com>
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P Please strive to live sustainably.
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From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto: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<mailto: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<mailto:pasha.pkconsulting at gmail.com>>
To: eQUEST Users List <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>; Vikram Sami <vsami at lasarchitect.com<mailto: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<mailto: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<mailto: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<mailto: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<mailto:equest-users-bounces at lists.onebuilding.org> [equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Pasha Korber-Gonzalez [pasha.pkconsulting at gmail.com<mailto: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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