[Equest-users] UA Convergence Error

Tue Dec 10 09:22:18 PST 2019

Thanks Brian, glad to hear I'm not having hallucinations.  I don't think the sizing matters because I input the actual airflow, static pressure, cooling capacity and heating capacity.
I seem to be making progress by changing some of the inputs.
Regards,

Paul Diglio
87 Fairmont Avenue 
New Haven, CT 06513 

203-415-0082 

    On Tuesday, December 10, 2019, 11:34:06 AM EST, Brian Fountain <brian.fountain at sa-footprint.com> wrote:  

Paul,

I have seen this error in 2.3 … and have had it crop up with small changes to the building/model as you describe.  I am struggling to remember how we got past it.  

I believe it has to do with the new sizing routine for air handling units.  I was hoping Doug Maddox would jump into the conversation.  (he has a video at maddoxenergy.com on the sizing routine but it does not address this issue specifically)

A couple of questions:

1)     Do you have heating and cooling design days set up?  I would recommend this. (otherwise it runs the whole year for sizing).

2)       

I will continue to try and remember which project(s) this came up on and how we resolved it.  Sorry I am not more help but you aren’t alone (which also doesn’t help).

Brian

Footprint

Brian Fountain
Associate
d416 572 8501 m416 562 6831

From: Equest-users <equest-users-bounces at lists.onebuilding.org>On Behalf Of Paul Diglio via Equest-users
Sent: Tuesday, December 10, 2019 11:07 AM
To: David Eldridge <DEldridge at grummanbutkus.com>
Cc: Sharad Kumar <sharadcapricious at gmail.com>; equest-users <equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] UA Convergence Error

CAUTION: EXTERNAL SENDER 

Hi David:

No heat exchangers in the .inp file.

Thank you,

Paul Diglio
87 Fairmont Avenue 
New Haven, CT 06513 

203-415-0082

On Tuesday, December 10, 2019, 10:46:12 AM EST, David Eldridge <deldridge at grummanbutkus.com> wrote:

I didn’t think of this earlier, but search the *.inp to see if one is in there associated with the AHU that crashes, maybe some relic code is in the file that isn’t shown in the UI.

DSE Mobile

773.490.5038

On Dec 10, 2019, at 9:30 AM, Paul Diglio via Equest-users <equest-users at lists.onebuilding.org> wrote:

Hi Sharad:

I can't find any heat exchangers in my model.  How did you pull up the heat exchanger screen?

Thank you,

Paul Diglio
87 Fairmont Avenue 
New Haven, CT 06513 

On Tuesday, December 10, 2019, 9:29:01 AM EST, Sharad Kumar via Equest-users <equest-users at lists.onebuilding.org> wrote: 

Hi Paul,

I think the problem is being caused due to some heat exchanger kind of thing being modeled in the built.

I am guessing out the problem as follows:

The UA calculations does not converge as there can be might possibility that then UA product and after multiplication with delta T does not converge with the meeting of the capacity as the formula is Q= U* A* delta T.

Q=  Capacity

UA= product of conductance and cross sectional area.

delta T= Temperature difference between ends.

<image.png>

Hence try to succumb with the problem in lieu-wise as above.

<image.png>

The other factors to have the UA product calculations to be right are as in above help page super-script which might can also guide as there are other factors based calculations is there as if there the boxed figure are outrun.

Hope this might help.

Thanks and regards,

Sharad.Kumar

Freelancer-Energy Simulation and Day-lighting.

.....................................................................................................................................................

---------- Forwarded message ----------
From: Paul Diglio <paul.diglio at sbcglobal.net>
To: Equest-users <equest-users at lists.onebuilding.org>
Cc: 
Bcc: 
Date: Mon, 9 Dec 2019 11:13:13 +0000 (UTC)
Subject: [Equest-users] UA Convergence Error

Hi Folks:

I am getting a "heat exchanger XX Sys1 UA calculation failed to converge" error.  The model has three building in it and only two air handlers per building.  I don't have any heat exchangers attached to the air handlers or any heat recovery installed.

Sometimes the error occurs when I change the glass type via the library and other times I get the error when I adjust the air changes per hour in one or two zones.

In the example above, the error was for system B2, but it varies...sometimes systems A or C 1 or 2.

Any ideas what the problem could be?  

Thank you,

Paul Diglio
87 Fairmont Avenue 
New Haven, CT 06513 

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