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<p>Adrian,</p>
<p> When a simulation doesn't converge it just keeps the values that
it calculated for the outputs of its most recent iteration and
goes on to the next timestep. You are very likely to see outputs
that don't match each other (a controller might calculate an "off"
output while the heat pump might have last calculated its "on"
state). The mathematics of the models are not likely the problem.
<br>
</p>
<p> Make sure that you are using a small time step (1-3 minutes) and
that you have thermal capacitance in all of your flow loops.</p>
<p>kind regards,</p>
<p> David</p>
<p> <br>
</p>
<div class="moz-cite-prefix">On 07/07/2020 18:15, Adrian Riebel
Brummer via TRNSYS-users wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAO+M903yMk4PrjT6SRqDcECUsjqZgJH1t74tBGn-hBq48t+mBA@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr"><br>
<div>Hello Jeff,</div>
<div><br>
</div>
<div>thanks very much for your answer. Maybe I didn't explain
myself very well.</div>
<div><br>
</div>
<div>The waterflow of the heat pump is zero because the pump
which controls the flow is turned off. The control signals of
the heat pump (heating and cooling control signals) are zero
too, so the heat pump should be turned off and nothing should
happen. The problem is, the outlet temperature of the heat
pump is unstable. I think the reason is that the heat pump is
not completely turned off and is trying to solve this
equation:</div>
<div><br>
</div>
<div>
<div><img src="cid:part1.93D6196B.A62BBD16@tess-inc.com"
alt="image.png" class="" width="370" height="111"><br>
</div>
</div>
<div><br>
</div>
<div>Obviously the equation can't be solved because m_dot_liq is
zero, but the heat pump shouldn't be trying to solve it
either.</div>
<div><br>
</div>
<div>As I said before, the documentation says something about a
"Fan Control Signal" which should be set to zero, in order
that the heat pump doesn't make any calculations. The problem
is, I can't find that input when I look for it in the
Simulation Studio.</div>
<div><br>
</div>
<div>I hope that I managed to explain myself well (English is
not my native language). I would be very grateful if you can
tell me if I'm wrong or what should I do.</div>
<div><br>
</div>
<div>Thanks very much,</div>
<div><br>
</div>
<div>Adrian Riebel</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
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<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">El mar., 7 jul. 2020 a las
13:40, Jeff Thornton via TRNSYS-users (<<a
href="mailto:trnsys-users@lists.onebuilding.org"
moz-do-not-send="true">trnsys-users@lists.onebuilding.org</a>>)
escribió:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p>Adrian,</p>
<p>Any flow convergence issues you are having is likely due
to something beyond the AWHP. This type does not set the
water flow rate - it simply passes it through the device;
heating or cooling it of the device is on or simply just
passing it through if the device is off. Pumps are the
devices in TRNSYS that typically set the flow rates for
your loops. I would suggest you use the TRACE feature and
watch to see what is happening when you are getting
convergence issues.</p>
<p> </p>
<p>Jeff</p>
<p> </p>
<div>
<pre>---
Jeff Thornton
President - TESS LLC
3 N. Pinckney Street, Suite 202, Madison WI USA 53703
Office: (608) 274-2577 Fax: (608) 278-1475
<a href="http://www.tess-inc.com" target="_blank" moz-do-not-send="true">www.tess-inc.com</a>
E-Mail: <a href="mailto:thornton@tess-inc.com" target="_blank" moz-do-not-send="true">thornton@tess-inc.com</a>
</pre>
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<p>On 07/05/2020 7:36 pm, Adrian Riebel Brummer via
TRNSYS-users wrote:</p>
<blockquote type="cite"
style="padding-left:5px;border-left:2px solid
rgb(16,16,255);margin-left:5px">
<div dir="ltr">
<div>Dear TRNSYS users,</div>
<div> </div>
<div>I have a problem with Type 941 (Air-Water Heat
Pump). My problem is that the simulation doesn't
converge when the waterflow in the heat pump is zero,
despite the heat pump is also in off mode (heating and
cooling control signals are both set to zero).</div>
<div> </div>
<div>I have read the mathematical reference of this Type
and it says something about a "Fan control signal",
which functions, as I understand, as the master on-off
switch of the heat pump. The problem is that I can't
find that Input in the TRNSYS programm.</div>
<div> </div>
<div>I would like to know why I can't find that Input,
and why the model doesn't converge despite the heat
pump shouldn't be doing anything.</div>
<div> </div>
<div>I send you a picture of all the inputs that I can
see for this Type. I have TRNSYS18 and TessLibs17.</div>
<div> </div>
<div>Regards,</div>
<div> </div>
<div>Adrian Riebel</div>
<div> </div>
<div>
<div><img
src="cid:part8.6D10D36F.D550A61C@tess-inc.com"
alt="image.png" class="" width="417" height="520"></div>
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<pre class="moz-signature" cols="72">--
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
3 North Pinckney Street - suite 202
Madison, WI 53703 USA
P:+1.608.274.2577
F:+1.608.278.1475
<a class="moz-txt-link-abbreviated" href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a>
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