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<div class=Section1>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>John,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The design/max ratio is exactly what I’m discussing below when I
say “DESIGN-PLR ratio,” so we’re definitely in the same ballpark =).<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I’d like to apply/paraphrase your advice to a few conditions to be
sure I’m getting it correctly: <o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>-<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If we create all 3 custom curves, and normalize each to a point
at maximum (not design) capacity, then the design-to-max ratio (DESIGN-PLR)
should be set to 1.00.<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>-<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If we create <u>only</u> the part load efficiency curve
(EIR-FPLR or EIR-FPLR&dT), and wish to use the library defaults for EIR-FT
and CAP-FT, then we should normalize this curve’s data points to ARI conditions
(as that’s what the library curves are normalized to, per James’s email – I think
I’ve read this somewhere also), specify an ARI capacity, EIR and conditions on
the basic specifications tab, and enter a DESIGN-PLR of [ARI capacity/maximum
capacity (for the same conditions)].<o:p></o:p></span></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><span
style='mso-list:Ignore'>-<span style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>If we create all 3 custom curves, and try to normalize each to
either ARI or design conditions, then we should specify capacity, EIR, CHWT,
CWT and condenser GPM corresponding to either the ARI or design conditions of
that normalizing point. In that case, we also specify a DESIGN-PLR using
either the ARI or design capacity divided by the maximum capacity for the same
conditions.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><u><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Profound (to me) Conclusion</span></u><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>: In <u>No</u>
instance should we <u>Ever</u> attempt creating custom curves and NOT have at
least one run from our manufacturer telling us what the maximum (not design)
capacity is for the normalizing point. This conclusion would only apply to centrifugal
chillers only.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Does this all sound right?<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>~Nick<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>James, <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Yeah, if all the part load data you received held the same CHWT
and CWT equal, you might be able to make your part-load curve if it could have
been a quadratic EIR-FPLR curve (like a reciprocating chiller), but not a bi-quadratic
EIR-FPLR&dT (as with my centrifugal VSD chiller). You definitely could not
approach generating custom EIR-FT or CAP-FT curves without varying condenser
and chilled water temps. That exact issue happened to me the first few times I
tried to reign my chiller reps in =). <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>This time, I convinced my rep to give me multiple part load runs
holding the CHWT constant and varying the CWT incrementally. This let me build
the bi-quadratic EIR-FPLR&dT curve as I had at least three different dT’s
represented in my part load data points. I plotted the 3D curve in excel to
check my work and darned if the generated coefficients seem to be really
accurate =)! It’s currently looking like a bittersweet revelation however –
the library curve for a water-cooled centrifugal VSD chiller (see attached
visualization) seems a LOT more generous (more efficient) at low part loads
than the one I’ve generated which matches my rep’s data… I might share a
visual of my custom curve for comparison once I’m dead-sure it’s accurate – I’m
trying to clarify a few things with my rep right now.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>~Nick<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><img width=119 height=37 id="Picture_x0020_1"
src="cid:image001.jpg@01CB7B43.D7448B90" alt="cid:489575314@22072009-0ABB"></span><b><span
style='font-size:11.0pt;font-family:"Stylus BT","sans-serif";color:#2D4D5E'><o:p></o:p></span></b></p>
<p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Stylus BT","sans-serif";
color:#2D4D5E'><o:p> </o:p></span></b></p>
<p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Stylus BT","sans-serif";
color:#2D4D5E'>NICK CATON, E.I.T.</span></b><b><span style='font-family:"Stylus BT","sans-serif";
color:#2D4D5E'><o:p></o:p></span></b></p>
<p class=MsoNormal><span style='font-size:7.5pt;font-family:"Calibri","sans-serif";
color:#CC9900'>PROJECT ENGINEER</span><span style='font-size:7.5pt;color:#CC9900'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>25501 west valley parkway<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>olathe ks 66061<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>direct 913 344.0036<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>fax 913 345.0617<o:p></o:p></span></p>
<p class=MsoNormal><i><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>Check out our new web-site @ </span></i><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><a
href="www.smithboucher.com" title="blocked::www.smithboucher.com"><span
style='font-size:10.0pt'>www.smithboucher.com</span></a></span><u><span
style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:blue'> </span></u><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> John T. Forester
[mailto:JohnTF@BVHis.com] <br>
<b>Sent:</b> Wednesday, November 03, 2010 10:29 AM<br>
<b>To:</b> Nick Caton; equest-users@lists.onebuilding.org<br>
<b>Subject:</b> RE: [Equest-users] Chiller Curves (oh boy!)<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'>Nick,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'>When defining a centrifugal chiller in eQuest, one of the items on
the Basic Specifications tab under the Design vs. Rated Conditions is a
Design/Max Cap ratio. By default, this is 92% for a water cooled
unit. I believe this gets at the discussion in the help pages that talks
about maximum capacity versus design capacity and how the chiller vendor will
spec a piece of equipment. Typically, vendors don’t often get asked (or
provide) what the “Maximum” capacity of a spec’d unit is. Therefore the
performance data that they provide are at “design conditions.”<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'>If you change the chiller type to a reciprocating chiller, this
“Design/Max Cap” ratio is disabled and the default specified condition changes from
“Design Conditions” to “Rated Conditions.” This suggests that there is
little “extra” capacity when a selection is done for that type of chiller.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'>If you do get “maximum capacity” data and create curves from that
data, you will want to change the Design/Max Cap ratio to 1.0 so eQuest knows
that there isn’t any spare capacity at the chiller. Also if the data
points you are using to normalize your curves are different than the design
conditions for your energy model, you will want to change the “Chiller
Specified at” value to “Rated Conditions” and enter the rated conditions for
CHW temp, CW temp and CW gpm/ton to match your normalized curves.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'>Hope this helps,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'>John<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal><span style='font-size:8.5pt;font-family:"Arial","sans-serif";
color:gray'>John T. Forester, P.E., LEED AP, Mechanical Design Engineer </span><strong><span
style='font-size:8.5pt;font-family:"Arial","sans-serif";color:#0000A0'>I BVH
Integrated Services I</span></strong><strong><span style='font-size:8.5pt;
font-family:"Arial","sans-serif";color:black'> </span></strong><span
style='font-size:8.5pt;font-family:"Arial","sans-serif";color:gray'>617.658.9008
tel </span><strong><span style='font-size:8.5pt;font-family:"Arial","sans-serif";
color:#0000A0'>I</span></strong><strong><span style='font-size:8.5pt;
font-family:"Arial","sans-serif";color:gray'> </span></strong><span
style='font-size:8.5pt;font-family:"Arial","sans-serif";color:gray'>617.244.3753
fax</span><span style='font-size:8.5pt;font-family:"Arial","sans-serif";
color:#0000A0'> <strong><span style='font-family:"Arial","sans-serif"'>I</span></strong></span><strong><span
style='font-size:8.5pt;font-family:"Arial","sans-serif";color:gray'> </span></strong><span
style='font-size:8.5pt;font-family:"Arial","sans-serif";color:gray'>One Gateway
Center Suite 506, Newton MA 02458 </span><strong><span style='font-size:8.5pt;
font-family:"Arial","sans-serif";color:#0000A0'>I <a href="http://www.bvhis.com">www.bvhis.com</a> I
Hartford ● New Haven ● Boston</span></strong><span style='color:gray'><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal align=center style='text-align:center'><hr size=2
width="100%" align=center tabindex=-1> <o:p></o:p></p>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> equest-users-bounces@lists.onebuilding.org
[mailto:equest-users-bounces@lists.onebuilding.org] <b>On Behalf Of </b>Nick
Caton<br>
<b>Sent:</b> Wednesday, November 03, 2010 11:03 AM<br>
<b>To:</b> Carol Gardner; equest-users@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Equest-users] Chiller Curves (oh boy!)</span><o:p></o:p></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Thanks for the response Carol!<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>That 120% load case is what I’m getting at – let me try to
explain a little further:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>In the DOE2 help files, the vocabulary for centrifugal chillers
is “design capacity” and “maximum capacity,” where “design” means the capacity
at the rated or designed conditions (at which you define / specify your
chiller), and “maximum” means the capacity the chiller is really capable of
under the same conditions if it runs balls-out (maximum power to the
refrigerant drive).<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>The help file excerpt I copied below with the red line is pretty
explicitly telling us to normalize the part load values to the <u>maximum</u>
capacity for centrifugal chillers. I’ve highlighted a second line for
clarity. The EDR guidelines I linked below are saying you can instead
normalize to the <u>design</u> capacity for the EIR-PLR curve if that’s all
your field measurements or manufacturer rep can provide.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I’m asking – are both approaches right? <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>My first and second questions are kinda tied together… How would
choosing to normalize to either the maximum or design conditions affect how we
should handle the DESIGN-PLR ratio, if at all?<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>~Nick.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><img border=0 width=119 height=37 id="Picture_x005f_x0020_1"
src="cid:image001.jpg@01CB7B43.D7448B90" alt="cid:489575314@22072009-0ABB"></span><b><span
style='font-size:11.0pt;font-family:"Stylus BT","sans-serif";color:#2D4D5E'><o:p></o:p></span></b></p>
<p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Stylus BT","sans-serif";
color:#2D4D5E'><o:p> </o:p></span></b></p>
<p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Stylus BT","sans-serif";
color:#2D4D5E'>NICK CATON, E.I.T.</span></b><b><span style='font-family:"Stylus BT","sans-serif";
color:#2D4D5E'><o:p></o:p></span></b></p>
<p class=MsoNormal><span style='font-size:7.5pt;font-family:"Calibri","sans-serif";
color:#CC9900'>PROJECT ENGINEER</span><span style='font-size:7.5pt;color:#CC9900'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>25501 west valley parkway<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>olathe ks 66061<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>direct 913 344.0036<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>fax 913 345.0617<o:p></o:p></span></p>
<p class=MsoNormal><i><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#2D4D5E'>Check out our new web-site @ </span></i><span style='font-size:
11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><a
href="www.smithboucher.com" title="blocked::www.smithboucher.com"><span
style='font-size:10.0pt'>www.smithboucher.com</span></a></span><u><span
style='font-size:10.0pt;font-family:"Calibri","sans-serif";color:blue'> </span></u><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Carol Gardner
[mailto:cmg750@gmail.com] <br>
<b>Sent:</b> Tuesday, November 02, 2010 10:04 PM<br>
<b>To:</b> Nick Caton<br>
<b>Cc:</b> equest-users@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Equest-users] Chiller Curves (oh boy!)<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'>Let me take a crack at this. If
by design capacity you mean the chiller running at 100% load, you would create
the curve(s) by normalizing around your ARI design conditions i.e. the PLR
curve would be 1.0 at this point, call it ARI Cap and the other points would be
90% Cap/ARI Cap, 80% Cap/ARI Cap, etc. The same would go for your temp curves.
If, however, your chiller is operating at 120%, or some such other level, I
would normalize the curve around the ARI design conditions of the chiller at
120%. I had to do this for a VRV hp that was selected at the 120% design
condition.<br>
<br>
I find this from the DOE2 manual the most helpful:<o:p></o:p></p>
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<p class=MsoNormal><a href="volume2dictionary.htm">Volume 2: Dictionary</a><span
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<h5>INDEPENDENT-2<o:p></o:p></h5>
<p class=MsoBodyText>Used for all <span style='color:white;background:#316AC5'>curves</span>
having two independent variables. A list of up to twenty values of the second
independent variable. The number of values should be the same as for DEPENDENT.<o:p></o:p></p>
<p class=MsoBodyText><b><span style='font-family:"Arial","sans-serif"'>Example
1</span></b>: defining a <span style='color:white;background:#316AC5'>curve</span>
by inputting a set of data points.<o:p></o:p></p>
<p class=MsoBodyText>A packaged system (PZS) has cooling performance
significantly different from that used in the default model. The
manufacturer lists the data shown in Table 46, for cooling capacity, at 2000
cfm design air flow rate, as a function of outside dry-bulb temperature and
entering wet-bulb temperature.<o:p></o:p></p>
<p class=MsoCaption><a name="_Ref490744859"></a><a name="_Ref490744804"></a>Table
46 Cooling capacity (kBtu/hr) vs. temperature<o:p></o:p></p>
<div style='margin-top:2.0pt;margin-bottom:2.0pt'>
<div align=center>
<table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0
style='border-collapse:collapse'>
<tr style='page-break-inside:avoid'>
<td width=96 rowspan=2 valign=top style='width:1.0in;border:solid windowtext 1.0pt;
background:aqua;padding:0in 5.4pt 0in 5.4pt;background-position-x:0%;
background-position-y:0%;background-attachment:scroll'>
<p class=tabledata align=center style='margin-top:0in;text-align:center'><b>Outside<br>
Dry-bulb</b><o:p></o:p></p>
</td>
<td width=288 colspan=3 valign=top style='width:3.0in;border-top:solid windowtext 1.0pt;
border-left:none;border-bottom:none;border-right:solid windowtext 1.0pt;
background:aqua;padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color -moz-use-text-color;
background-position-x:0%;background-position-y:
0%;background-attachment:
scroll'>
<p class=tabledata align=center style='text-align:center'><b>Entering
Wet-bulb</b><o:p></o:p></p>
</td>
</tr>
<tr style='page-break-inside:avoid'>
<td width=96 valign=top style='width:1.0in;border:none;border-bottom:solid windowtext 1.0pt;
background:aqua;padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color -moz-use-text-color windowtext;
background-position-x:0%;background-position-y:
0%;background-attachment:
scroll'>
<p class=tabledata align=center style='text-align:center'><b>72F</b><o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-bottom:solid windowtext 1.0pt;
background:aqua;padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color -moz-use-text-color windowtext;
background-position-x:0%;background-position-y:
0%;background-attachment:
scroll'>
<p class=tabledata align=center style='text-align:center'><b>67F</b><o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border-top:none;border-left:none;
border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
background:aqua;padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext windowtext -moz-use-text-color;
background-position-x:0%;background-position-y:
0%;background-attachment:
scroll'>
<p class=tabledata align=center style='text-align:center'><b>62F</b><o:p></o:p></p>
</td>
</tr>
<tr>
<td width=96 valign=top style='width:1.0in;border-top:none;border-left:solid windowtext 1.0pt;
border-bottom:none;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;
border-color:-moz-use-text-color windowtext'>
<p class=tabledata align=center style='text-align:center'>85F<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>69<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>65<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-right:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext -moz-use-text-color -moz-use-text-color'>
<p class=tabledata align=center style='text-align:center'>60<o:p></o:p></p>
</td>
</tr>
<tr>
<td width=96 valign=top style='width:1.0in;border-top:none;border-left:solid windowtext 1.0pt;
border-bottom:none;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;
border-color:-moz-use-text-color windowtext'>
<p class=tabledata align=center style='text-align:center'>95F<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>68<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>63 (ARI)<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-right:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext -moz-use-text-color -moz-use-text-color'>
<p class=tabledata align=center style='text-align:center'>57<o:p></o:p></p>
</td>
</tr>
<tr>
<td width=96 valign=top style='width:1.0in;border-top:none;border-left:solid windowtext 1.0pt;
border-bottom:none;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;
border-color:-moz-use-text-color windowtext'>
<p class=tabledata align=center style='text-align:center'>105F<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>65<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>60<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-right:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext -moz-use-text-color -moz-use-text-color'>
<p class=tabledata align=center style='text-align:center'>53<o:p></o:p></p>
</td>
</tr>
<tr>
<td width=96 valign=top style='width:1.0in;border:solid windowtext 1.0pt;
border-top:none;padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext windowtext'>
<p class=tabledata align=center style='text-align:center'>115F<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-bottom:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color -moz-use-text-color windowtext'>
<p class=tabledata align=center style='text-align:center'>62<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-bottom:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color -moz-use-text-color windowtext'>
<p class=tabledata align=center style='text-align:center'>55<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border-top:none;border-left:none;
border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext windowtext -moz-use-text-color'>
<p class=tabledata align=center style='margin-bottom:0in;margin-bottom:.0001pt;
text-align:center'>49<o:p></o:p></p>
</td>
</tr>
</table>
</div>
</div>
<p class=MsoBodyText> <o:p></o:p></p>
<p class=MsoBodyText>In this example the independent variables are the entering
wet-bulb temperature and the outside dry-bulb temperature. Because there are
two independent variables and they have units of temperature, we input a <span
style='color:white;background:#316AC5'>curve</span> of TYPE BI-QUADRATIC-T
using the given data points. The dependent variable is not the cooling capacity
listed in the table but rather the cooling capacity divided by the cooling
capacity at the ARI rating point (95 F outside dry-bulb and 67 F entering
wet-bulb). In other words, the capacities should be normalized to the ARI
rating point., as shown in Table 47<o:p></o:p></p>
<p class=MsoCaption><a name="_Ref490745029">Table </a>47 Normalized
capacity vs. temperature<o:p></o:p></p>
<div style='margin-top:2.0pt;margin-bottom:2.0pt'>
<div align=center>
<table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0
style='border-collapse:collapse'>
<tr style='page-break-inside:avoid'>
<td width=96 rowspan=2 valign=top style='width:1.0in;border:solid windowtext 1.0pt;
background:aqua;padding:0in 5.4pt 0in 5.4pt;background-position-x:0%;
background-position-y:0%;background-attachment:scroll'>
<p class=tabledata align=center style='margin-top:0in;text-align:center'><b>Outside<br>
Dry-bulb</b><o:p></o:p></p>
</td>
<td width=288 colspan=3 valign=top style='width:3.0in;border-top:solid windowtext 1.0pt;
border-left:none;border-bottom:none;border-right:solid windowtext 1.0pt;
background:aqua;padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color -moz-use-text-color;
background-position-x:0%;background-position-y:
0%;background-attachment:
scroll'>
<p class=tabledata align=center style='text-align:center'><b>Entering
Wet-bulb</b><o:p></o:p></p>
</td>
</tr>
<tr style='page-break-inside:avoid'>
<td width=96 valign=top style='width:1.0in;border:none;border-bottom:solid windowtext 1.0pt;
background:aqua;padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color -moz-use-text-color windowtext;
background-position-x:0%;background-position-y:
0%;background-attachment:
scroll'>
<p class=tabledata align=center style='text-align:center'><b>72F</b><o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-bottom:solid windowtext 1.0pt;
background:aqua;padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color -moz-use-text-color windowtext;
background-position-x:0%;background-position-y:
0%;background-attachment:
scroll'>
<p class=tabledata align=center style='text-align:center'><b>67F</b><o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border-top:none;border-left:none;
border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
background:aqua;padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext windowtext -moz-use-text-color;
background-position-x:0%;background-position-y:
0%;background-attachment:
scroll'>
<p class=tabledata align=center style='text-align:center'><b>62F</b><o:p></o:p></p>
</td>
</tr>
<tr>
<td width=96 valign=top style='width:1.0in;border-top:none;border-left:solid windowtext 1.0pt;
border-bottom:none;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;
border-color:-moz-use-text-color windowtext'>
<p class=tabledata align=center style='text-align:center'>85F<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>1.095<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>1.032<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-right:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext -moz-use-text-color -moz-use-text-color'>
<p class=tabledata align=center style='text-align:center'>0.952<o:p></o:p></p>
</td>
</tr>
<tr>
<td width=96 valign=top style='width:1.0in;border-top:none;border-left:solid windowtext 1.0pt;
border-bottom:none;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;
border-color:-moz-use-text-color windowtext'>
<p class=tabledata align=center style='text-align:center'>95F<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>1.079<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>1.0 (ARI)<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-right:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext -moz-use-text-color -moz-use-text-color'>
<p class=tabledata align=center style='text-align:center'>0.905<o:p></o:p></p>
</td>
</tr>
<tr>
<td width=96 valign=top style='width:1.0in;border-top:none;border-left:solid windowtext 1.0pt;
border-bottom:none;border-right:solid windowtext 1.0pt;padding:0in 5.4pt 0in 5.4pt;
border-color:-moz-use-text-color windowtext'>
<p class=tabledata align=center style='text-align:center'>105F<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>1.032<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;padding:0in 5.4pt 0in 5.4pt'>
<p class=tabledata align=center style='text-align:center'>0.952<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-right:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext -moz-use-text-color -moz-use-text-color'>
<p class=tabledata align=center style='text-align:center'>0.841<o:p></o:p></p>
</td>
</tr>
<tr>
<td width=96 valign=top style='width:1.0in;border:solid windowtext 1.0pt;
border-top:none;padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext windowtext'>
<p class=tabledata align=center style='text-align:center'>115F<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-bottom:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color -moz-use-text-color windowtext'>
<p class=tabledata align=center style='text-align:center'>0.984<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border:none;border-bottom:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color -moz-use-text-color windowtext'>
<p class=tabledata align=center style='text-align:center'>0.873<o:p></o:p></p>
</td>
<td width=96 valign=top style='width:1.0in;border-top:none;border-left:none;
border-bottom:solid windowtext 1.0pt;border-right:solid windowtext 1.0pt;
padding:0in 5.4pt 0in 5.4pt;border-color:-moz-use-text-color windowtext windowtext -moz-use-text-color'>
<p class=tabledata align=center style='margin-bottom:0in;margin-bottom:.0001pt;
text-align:center'>0.778<o:p></o:p></p>
</td>
</tr>
</table>
</div>
</div>
<p class=MsoBodyText> <o:p></o:p></p>
<p class=MsoBodyText>The <span style='color:white;background:#316AC5'>CURVE</span>-<span
style='color:white;background:#316AC5'>FIT</span> input will look like the
following:<o:p></o:p></p>
<p class=doe-2input>CAP-<span style='color:white;background:#316AC5'>CURVE</span>-1
= <span style='color:white;background:#316AC5'>CURVE</span>-<span
style='color:white;background:#316AC5'>FIT</span><br>
TYPE
= BI-QUADRATIC-T<br>
INPUT-TYPE = DATA<br>
DEPENDENT =
(1.000,1.079,0.905,1.032,0.952,0.841,<br>
0.984,0.873,0.778,1.095,1.032,0.952) ..<br>
IN-TEMP1 =
( 67, 72, 62, 72,
67, 62,<br>
72, 67, 62,
72, 67, 62) ..<br>
IN-TEMP2 =
( 95, 95, 95, 105, 105,
105,<br>
115, 115, 115,
85 85, 85) ..<o:p></o:p></p>
<p class=MsoBodyText><b><span style='font-family:"Arial","sans-serif"'>Example
2:</span></b> Defining a <span style='color:white;background:#316AC5'>curve</span>
by inputting coefficients<o:p></o:p></p>
<p class=MsoBodyText>We want a furnace to have a constant efficiency as a
function of part load. To do this we must replace the default FURNACE-HIR-FPLR
with a <span style='color:white;background:#316AC5'>curve</span> that will give
a constant efficiency. The <span style='color:white;background:#316AC5'>curve</span>
TYPE is QUADRATIC in the part load ratio (PLR). PLR correction <span
style='color:white;background:#316AC5'>curves</span> are always multiplied by
the unit capacity, not the load, to obtain the energy (fuel or electricity)
use. Thus the <span style='color:white;background:#316AC5'>curve</span> we want
is: 0.0 + 1.0*PLR + 0.0*PLR*PLR. The input will look like:<o:p></o:p></p>
<p class=doe-2input>New-Furnace-HIR-fPLR = <span style='color:white;background:
#316AC5'>CURVE</span>-<span style='color:white;background:#316AC5'>FIT</span><br>
TYPE
= QUADRATIC<br>
INPUT-TYPE = COEFFICIENTS<br>
COEFFICIENTS = (0.0,1.0,0.0) ..<o:p></o:p></p>
<p class=MsoBodyText>Then in the SYSTEM command we include:<o:p></o:p></p>
<p class=doe-2input> FURNACE-HIR-FPLR = New-Furnace-HIR-fPLR<o:p></o:p></p>
</div>
<p class=MsoNormal style='margin-bottom:12.0pt'><o:p> </o:p></p>
<div>
<p class=MsoNormal>On Tue, Nov 2, 2010 at 3:21 PM, Nick Caton <<a
href="mailto:ncaton@smithboucher.com">ncaton@smithboucher.com</a>> wrote:<o:p></o:p></p>
<div>
<div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'>Hi everyone!</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'>I think I have <u>finally</u> wrapped my mind completely
around custom chiller performance curves for a centrifugal VSD chiller.
I’ve got a few specific questions now that I’m on the other side of the fence:</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'> </span><o:p></o:p></p>
<p><span style='color:#1F497D'>1.</span><span style='font-size:7.0pt;
color:#1F497D'> </span><span
style='color:#1F497D'>Is it necessary for the data points of a part load
efficiency curve (EIR-FPLR&dT in my case) to originate from data with a 1.0
(100%) PLR ratio corresponding to a maximum vs. a design load capacity?
From what I gather in <a
href="http://www.energydesignresources.com/Portals/0/documents/DesignGuidelines/EDR_DesignGuidelines_%20HVAC_Simulation.pdf"
target="_blank">the EDR reference</a> (re: “Method 2” on PDF page 32/65), this
curve can be generated using part-load readings assuming a <u>design</u>
capacity at the 100% loading mark… but the DOE2 help entry for “EIR-FPLR” seems
to suggest otherwise (copied below – see highlighted line).</span><o:p></o:p></p>
<p><span style='color:#1F497D'>2.</span><span style='font-size:7.0pt;
color:#1F497D'> </span><span
style='color:#1F497D'>If the above part load efficiency curve is created based
on data where the 100% loading point corresponds to the maximum (not design)
capacity, should “DESIGN-PLR” (the ratio of design to maximum capacity) be set
to 1.00 and the capacity of the chiller be specified at its maximum (not
design) for the design/rated conditions? As I write this question it
sounds like I’m chasing my tail – someone straighten me out =)!</span><o:p></o:p></p>
<p><span style='color:#1F497D'>3.</span><span style='font-size:7.0pt;
color:#1F497D'> </span><span
style='color:#1F497D'>When you veterans finish a project with sets of custom
performance curves, do you have any suggestions for a naming scheme for future
reference/re-use? I’m currently thinking to keep the curves grouped in an
.inp snippet I for importing along with an equipment cutsheet… but I’m certain
I’ll forget the all the details as quickly as humanly possible when this
project is behind me…</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.25in'><span style='color:#1F497D'> ~Nick</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'> </span><o:p></o:p></p>
<div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='color:#1F497D'><img border=0 width=119 height=37 id="_x0000_i1026"
src="cid:image001.jpg@01CB7B43.D7448B90" alt="cid:489575314@22072009-0ABB"></span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
style='color:#2D4D5E'> </span></b><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
style='color:#2D4D5E'>NICK CATON, E.I.T.</span></b><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:7.5pt;color:#CC9900'>PROJECT ENGINEER</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:10.0pt;color:#2D4D5E'>25501 west valley parkway</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:10.0pt;color:#2D4D5E'>olathe ks 66061</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:10.0pt;color:#2D4D5E'>direct 913 344.0036</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:10.0pt;color:#2D4D5E'>fax 913 345.0617</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><i><span
style='font-size:10.0pt;color:#2D4D5E'>Check out our new web-site @ </span></i><span
style='color:#1F497D'><a href="http://www.smithboucher.com" target="_blank"
title="blocked::www.smithboucher.com"><span style='font-size:10.0pt'>www.smithboucher.com</span></a></span><u><span
style='font-size:10.0pt;color:blue'> </span></u><o:p></o:p></p>
</div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
style='font-size:10.0pt'>EIR-FPLR</span></b><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Takes
the U-name of a curve that adjusts the electric input ratio as a function of<o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-family:Symbol'>· </span><u>The part load
ratio (PLR)</u> – The PLR is defined as the ratio of the hourly load to
the hourly capacity; Load / Cap<sub>hour</sub><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:.5in'><span style='font-family:Symbol'>· </span><u>The
evaporator/condenser dT</u> - The temperature differential between the
condenser and leaving chilled-water. The meaning of the condenser
temperature varies according to condenser type. <o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;
margin-left:2.7pt'>For most chillers, the dT has a relatively small effect on
part-load performance. However, for variable-speed centrifugal chillers, the
effect of dT is as important as the PLR. This is because the pressure
rise across the impeller is proportional to the square of the impeller’s speed.
Unless some form on condenser temperature relief is employed to reduce the
temperature (and pressure) differential across the chiller at part load, the
performance of a variable-speed chiller may not be significantly different than
that of a constant-speed chiller.<o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>To
model power consumption as a function of the PLR only, use a CURVE-FIT of TYPE
= QUADRATIC or CUBIC. To model as a function of both PLR and dT, use a
BI-QUADRATIC-RATIO&DT curve. <b><span style='color:red'>The curve must be
normalized to 1.0 at full load and the rated temperature differential. <o:p></o:p></span></b></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
style='color:red'>Note that, for centrifugal chillers, ‘full load’ is defined
as the ‘maximum capacity’, not the ‘design capacity’.</span></b> Refer to the
DESIGN-PLR keyword for more information.<o:p></o:p></p>
<p style='margin-bottom:12.0pt'> <o:p></o:p></p>
</div>
</div>
<p class=MsoNormal style='margin-bottom:12.0pt'><br>
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</div>
<p class=MsoNormal><br>
<br clear=all>
<br>
-- <br>
Carol Gardner PE<o:p></o:p></p>
</div>
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