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<p>Ali,</p>
<p> Its hard to know what might be going on without looking in
detail at the project. A couple of pointers; apologies if some of
these are very basic. Usually the lower input temperature would be
set to the tank bottom temperature, not to the heat exchanger
outlet temperature. If your heat exchanger is in-tank (rather than
external) then this makes less of a difference. Bear in mind that
Type2 makes its control decision based only on a temperature
difference, not on a setpoint. If your collector pump is turning
on at -25C that means the heat exchanger outlet temperature is
even lower.</p>
<p> Types538 and 539 allow you to define thermal capacitance for
your collector whereas Type1 and Type50 neglect capacitance. In
your air-based system the capacitance may be less important.</p>
<p> If -25C is below the ambient temperature and the collector is
still turning on, have a look at the load side of your tank (or
heat exchanger). From what you describe, it sounds as though there
is something driving the tank/HX temperature unrealistically low
and that you may need to solve that side of the controls rather
than focusing on the collector side of them.</p>
<p>kind regards,</p>
<p> David</p>
<p><br>
</p>
On 08/08/2021 10:42, Ali Shahrouzian via TRNSYS-users wrote:<br>
<blockquote type="cite"
cite="mid:YTXPR0101MB21125B4A7DB6DC1FCCAED7D29CF59@YTXPR0101MB2112.CANPRD01.PROD.OUTLOOK.COM">
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<p class="MsoNormal">Dear TRNSYS users,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m modelling a solar system to heat a
space. It is consisting of two loops: one of them is a
water-based solar collector loop as heat source and the other
one is an air-based loop included an air-to-water HX, a fan
and so forth.<o:p></o:p></p>
<p class="MsoNormal">In order to control the solar loop in such
a way that it turns off when the incident radiation isn’t
sufficient (during night), I’ve used a differential controller
(type 2). I connected the collector outlet temperature to Th
(parameter 1 for type 2) and the HX outlet temperature to the
Tc (parameter 2). <o:p></o:p></p>
<p class="MsoNormal">Defining the controller in this same way
causes the collector outlet temperature starts from minus
temperatures like -25 degrees C over the course of winter
days. I face with this issue when I used types 50 (PV/T
collector), (538 evacuated collector), 539 and … , however
using type 1 (flat plate collector) as the solar collector
doesn’t cause this issue.<o:p></o:p></p>
<p class="MsoNormal">I would appreciate if anyone help me in
this case.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">And one more thing, as I’ve already
explained my system also has a secondary loop included a fan,
an air-to-water HX and … . I am wondering whether in order to
control the secondary loop when solar loop is off, I should
define a new controller (type 2) or I can use the differential
controller previous. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks in advance.<o:p></o:p></p>
<p class="MsoNormal">Ali<o:p></o:p></p>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
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</pre>
</blockquote>
<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
<a class="moz-txt-link-abbreviated" href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a>
<a class="moz-txt-link-freetext" href="http://www.tess-inc.com">http://www.tess-inc.com</a>
<a class="moz-txt-link-freetext" href="http://www.trnsys.com">http://www.trnsys.com</a></pre>
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