<html><body bgcolor="#FFFFFF"><div>This is generally an industry problem. Chillers are often designed with a PLR performane optimized at 50% of max load. This is because you want it to be most efficient in the area where it will be operating most of the time. These performance curves play a major role and are quite different from machine to machine. Traditionally we spec a max capacity and a COP, when actually we should be looking more closely at the part load ratios expected and those of the machine. <br><br>Sent from my iPhone</div><div><br>On 03.10.2012, at 19:06, David BRADLEY <<a href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a>> wrote:<br><br></div><div></div><blockquote type="cite"><div>
Juan Francisco,<br>
This is a very good question to which there are as many valid
responses as there are responders. My feeling is that traditional
methods for sizing cooling equipment lead to very over sized
equipment and the energy inefficiency that comes with it.
Traditional sizing involves a steady-state, worst-case scenario when
all the equipment is on, all the lights are on, and all the people
are in the building. Some tools also do not account for zone
adjacencies; they compute the worst case assuming that all zones are
thermally isolated from each other. There is no credit for thermal
mass and no credit for shading. That is obviously going to give you
the greatest possible cooling load. There are lots and lots of other
justifiable methods, some of which you mention. What I have done in
the past is to look at what the peak cooling load is under a number
of these methods (with normal building operation during an average
weather year, including shading, excluding shading, during an
"extreme" weather sequence of days, during a "design day" that
repeats itself. From multiple tests, you can get an idea of how
sensitive the peak cooling load is. You can then do some experiments
of limiting the available cooling power in order to see how badly
you miss your target cooling temperature. If the overshoot is small,
then under sizing the equipment a little bit will create energy
savings and the comfort penalty will not be great. With all that
information, it is then possible to do an informed sizing the
cooling equipment.<br>
Best,<br>
David<br>
<br>
<br>
<div class="moz-cite-prefix">On 10/3/2012 04:44, JUAN FRANCISCO
BELMONTE TOLEDO wrote:<br>
</div>
<blockquote cite="mid:2B4A46F4-ABB3-40B3-B654-64B5B3E815F6@mimectl" type="cite">
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<div dir="ltr"><font color="#000000" face="Century Schoolbook" size="3">Dear users.</font></div>
<div dir="ltr"> </div>
<div dir="ltr"><font face="Century Schoolbook">Any idea how to
make a good cooling peak load calculation with trnsys, in a
similar way as max. heat load calculation does in trnbuild?.</font></div>
<div dir="ltr"> </div>
<div dir="ltr"><font face="Century Schoolbook">I mean hipothesis
about Solar radiation (What values we must consider
and where we can find them), temperature (we consider a
sinusoidal wave shape <font face="Century Schoolbook">-as
EnergyPlus does-</font> or constant value, ...).., in
which months we must simulate (for example i´ve found many
building with higher values in September due to the Sun is
lower and they had a lot of windows,.. ), , tmy files
should not be used because are average values, or yes...etc.</font></div>
<div dir="ltr"> </div>
<div dir="ltr"><font face="Century Schoolbook">thank you.</font></div>
<div dir="ltr"><font face="Century Schoolbook">Regards.</font></div>
<div dir="ltr"> </div>
</div>
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<div><font color="#000000" face="Arial">
<div style="MARGIN: 0cm 0cm 0pt" class="MsoNormal"><em><span style="FONT-STYLE: normal; FONT-FAMILY: 'Comic Sans
MS'; COLOR: blue; FONT-SIZE: 8pt; mso-bidi-font-style:
italic"><font size="1">
<div dir="ltr">
<div><font color="#000000" face="Courier New" size="2"><strong>Juan Francisco Belmonte
Toledo</strong></font></div>
<div><font color="#000000" face="Courier New" size="2">Universidad de Castilla-La Mancha
(Spain)</font></div>
</div>
</font></span></em></div>
</font></div>
</div>
<br>
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<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"><a href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a></a>
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