<html><head></head><body><div class="ydpc5458919yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><div><div dir="ltr" data-setdir="false">Thanks so much Jeff, now it makes sense and I will try to find the dt problem/<br></div><div><br></div><div class="ydpc5458919signature">Paul Diglio<br>87 Fairmont Avenue <br>New Haven, CT 06513 <br><br>203-415-0082</div></div>
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On Tuesday, December 10, 2019, 8:22:18 PM EST, Jeff Hirsch <james.j.hirsch@gmail.com> wrote:
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<div>I do not believe that screen exists in 2.3 recent versions and it looks
like the version he is showing is from an older refrigeration version.</div>
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<div>The error you are getting is, I believe, generated during the air handler
coil design calculations when it is trying to find the effective heat exchanger
UA for the coil. It takes the flows and temperatures on each side of the surface
and solves for a UA that results in a capacity within .1% of the specified or
calculated required coil capacity. From the starting point “guess” (based on the
required capacity divided by the design dT) it tries 100 iterations of the
calculation each time altering the UA guess via an extrapolation or
interpolation based on the history of guesses.</div>
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<div>Perhaps it cannot find the UA in 100 iterations due to a mismatch between
some specified flow/temperatures values on either side of the HX surface ...
check your inputs for a dT too small or a specified flow or capacity that seems
incompatible with any specified or defaulted dT. We removed the HX input command
(and thus eQUEST dialog) back in 2010 and instead default the creation of each
HX during the design calculation phase – thus, unfortunately, the number of
iterations and max error are set in code (100 and 0.001%) and not user
changeable. Perhaps we need to reconsider that decision, but for now this
problem can only be fixed by getting dT’s, flows and capacities to be compatible
so a UA can be found within the iteration and tolerance limits.</div>
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<span style="FONT-FAMILY:calibri;FONT-WEIGHT:bold;"></span><span style="FONT-FAMILY:calibri;FONT-WEIGHT:bold;">Jeff Hirsch</span><br style="FONT-FAMILY:calibri;" clear="none"><span style="FONT-FAMILY:calibri;"></span><span style="FONT-FAMILY:calibri;">James J. Hirsch & Associates<br clear="none"></span><span style="FONT-FAMILY:calibri;">voice mail: (805) 553-9000<br clear="none"></span><span style="FONT-FAMILY:calibri;">mobile: (805) 532-1045<br clear="none"></span><span style="FONT-FAMILY:calibri;"></span><br style="FONT-FAMILY:calibri;" clear="none"><span style="FONT-FAMILY:calibri;"></span><span style="FONT-FAMILY:calibri;"></span><br style="FONT-FAMILY:calibri;" clear="none"><span style="FONT-FAMILY:calibri;"></span><span style="FONT-FAMILY:calibri;"></span></div>
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<div class="ydpc89da509yiv9887899821yqt0733041973" id="ydpc89da509yiv9887899821yqtfd20412"><div><b>From:</b> <a shape="rect" title="equest-users@lists.onebuilding.org">Paul Diglio via Equest-users</a> </div>
<div><b>Sent:</b> Tuesday, December 10, 2019 7:29 AM</div>
<div><b>To:</b> <a shape="rect" title="equest-users@lists.onebuilding.org">equest-users</a> ;
<a shape="rect" title="sharadcapricious@gmail.com">Sharad Kumar</a> </div>
<div><b>Subject:</b> Re: [Equest-users] UA Convergence Error</div></div></div></div><div class="ydpc89da509yiv9887899821yqt0733041973" id="ydpc89da509yiv9887899821yqtfd49106">
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<div dir="ltr">Hi Sharad:</div>
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<div dir="ltr">I can't find any heat exchangers in my
model. How did you pull up the heat exchanger screen?</div>
<div dir="ltr"> </div>
<div dir="ltr">Thank you,<br clear="none"></div>
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<div class="ydpc89da509yiv9887899821ydp9b35a8d3signature">Paul Diglio<br clear="none">87 Fairmont Avenue <br clear="none">New Haven,
CT 06513 <br clear="none"></div></div>
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<div>On Tuesday, December 10, 2019, 9:29:01 AM EST, Sharad Kumar via
Equest-users <equest-users@lists.onebuilding.org> wrote: </div>
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<div><font color="#073763">Hi Paul,</font></div>
<div><font color="#073763"><br clear="none"></font></div>
<div><span style="COLOR:rgb(7,55,99);">I think the problem is being caused due
to some heat exchanger kind of thing being modeled in the
built.</span><br clear="none"></div>
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<div><font color="#073763">I am guessing out the problem as follows:</font></div>
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<div><font color="#073763">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.</font></div>
<div><font color="#073763"><br clear="none"></font></div>
<div><font color="#073763">Q= Capacity</font></div>
<div><font color="#073763">UA= product of conductance and cross sectional
area.</font></div>
<div><font color="#073763">delta T= Temperature difference between
ends.</font></div>
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<div><font color="#073763"><img style="MAX-WIDTH:572px;WIDTH:534px;" alt="image.png" src="cid:6bd326bd-c122-ae0a-af2f-991b4839f6c4@yahoo.com" data-inlineimagemanipulating="true"><br clear="none"></font></div><font color="#073763">
</font></div>
<div><font color="#073763">Hence try to succumb with the problem in lieu-wise as
above.</font></div>
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<div><img style="MAX-WIDTH:386px;WIDTH:386px;" alt="image.png" src="cid:bb8f5497-b1e7-e307-426e-28b9b784b265@yahoo.com" data-inlineimagemanipulating="true" data-id="1576078910770"><br clear="none"></div></div>
<div><font color="#073763"><br clear="none"></font></div>
<div><font color="#073763">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.</font></div>
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<div><font color="#073763">Hope this might help.</font></div>
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<div><b><font color="#073763">Thanks and regards,</font></b></div>
<div><font color="#073763">Sharad.Kumar</font></div>
<div><font color="#073763">Freelancer-Energy Simulation and
Day-lighting.</font></div>
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<div dir="ltr"><b><font color="#20124d">....................................................................................................................................................</font></b>.</div>
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<div dir="ltr">---------- Forwarded message ----------<br clear="none">From: Paul Diglio <<a shape="rect">paul.diglio@sbcglobal.net</a>><br clear="none">To: Equest-users
<<a shape="rect">equest-users@lists.onebuilding.org</a>><br clear="none">Cc: <br clear="none">Bcc:
<br clear="none">Date: Mon, 9 Dec 2019 11:13:13 +0000 (UTC)<br clear="none">Subject: [Equest-users] UA
Convergence Error<br clear="none">
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<div dir="ltr">Hi Folks:</div>
<div dir="ltr"> </div>
<div dir="ltr">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.<br clear="none"></div>
<div dir="ltr"> </div>
<div dir="ltr">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.</div>
<div dir="ltr"> </div>
<div dir="ltr">In the example above, the error was for system B2, but it
varies...sometimes systems A or C 1 or 2.</div>
<div dir="ltr"> </div>
<div dir="ltr">Any ideas what the problem could be? <br clear="none"></div>
<div dir="ltr"> </div>
<div dir="ltr">Thank you,<br clear="none"></div>
<div> </div>
<div>Paul Diglio<br clear="none">87 Fairmont Avenue <br clear="none">New Haven, CT 06513
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