<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
Enyuan,<br>
The total cooling rate is the sensible and latent energy being
removed from the air stream by the active section of the heat pump.
It is computed as the mass flow rate of air multiplied by the
difference between the enthalpy of air leaving the heat pump and the
enthalpy of the mixed air (return + ambient) entering the
evaporator. The heat pump does not have any kind of economizer
controls built into it. The amount of outdoor air being mixed with
return air is simply a function of how you have set the outdoor air
damper position input. It could be that your heat pump is cooling
because there is no ambient air being mixed in and the heat pump is
working only with return air. If your concern is that the heat pump
would not operate when the ambient temperature is so low (because of
freeze up in the condenser) then you have to be careful of your
external data file. Performance is interpolated within the range of
data given in the file but it is not extrapolated beyond the range.
If the heat pump asks for cooling (because of the way you have set
the cooling signal input and fan control signal) then the
performance (cooling capacity and COP) will be returned for the
closest ambient temperature found in the data file.<br>
Regards,<br>
David<br>
<br>
<br>
<div class="moz-cite-prefix">On 11/19/2014 14:26, Enyuan Hu wrote:<br>
</div>
<blockquote
cite="mid:CAJud35Mn5zxh0TBft+O8oBJuVrtsVc_kWunR0E_tZjB=2jZZEw@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif;font-size:small;color:#3333ff">Dear
all,</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif;font-size:small;color:#3333ff"><br>
</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif;font-size:small;color:#3333ff">When
I'm using a type 954 air-to-air heat pump to condition a one
zone building, I found that even during the winter (ambient
temperature is below the cooling threshold), the 'total
cooling rate' output from the heat pump is positive instead of
being zero as expected. Can anyone help me explain why?
Thanks!</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif;font-size:small;color:#3333ff"><br>
</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif;font-size:small;color:#3333ff">best
regards,</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif;font-size:small;color:#3333ff">Enyuan
Hu</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
TRNSYS-users mailing list
<a class="moz-txt-link-abbreviated" href="mailto:TRNSYS-users@lists.onebuilding.org">TRNSYS-users@lists.onebuilding.org</a>
<a class="moz-txt-link-freetext" href="http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org">http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org</a>
</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
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>
<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>
</body>
</html>