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<TITLE>eQuest Default f(PLR) Skepticism</TITLE>
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<P><FONT SIZE=2 FACE="Arial">eQuest models boiler and chiller plants with default part load curves that I think may be incorrect. As I understand it, the f(PLR) curves are used as a direct multiplier on the HIR for boilers and EIR for chillers, with full load (1.0 PLR) corresponding to a 1.0 multiplier. If this is true, the f(PLR) curve should increase at part load for atmospheric boilers (atmospheric boilers become somewhat less efficient at part load). The default atmospheric boiler curve decreases almost linearly down to zero! I am having a tough time wrapping my head around this.</FONT></P>
<P><FONT SIZE=2 FACE="Arial">On the chiller side, the default f(PLR) is a bi-quadratic function using both dT and PLR as variables, so it is f(PLR,dT). Since I never have this dual function information in my general chiller selections, I have been using a standard f(PLR) function quoted at a fixed dT from the manufacturer. The curve I get from a McQuay 400-ton chiller selection is quadratic, with decreasing EIR down to 50% load and increasing EIR below 50% load. I seriously doubt that the eQuest default corresponds with this entry because changing the function produces a huge change in performance.</FONT></P>
<P><FONT SIZE=2 FACE="Arial">Do any of you have any thoughts or suggestions about the accuracy of default f(PLR) curves? Should I scrap my "improved," real curves - they are drastically changing the model performance?!?!</FONT></P>
<P><FONT SIZE=2 FACE="Arial">Taylor</FONT>
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<P><FONT SIZE=2 FACE="Arial">________________________________________________________</FONT>
<BR><FONT SIZE=2 FACE="Arial">Taylor Keep</FONT>
<BR><FONT SIZE=2 FACE="Arial">Mechanical, LEED® AP</FONT>
<BR><FONT SIZE=2 FACE="Arial"><U> </U></FONT>
<BR><FONT SIZE=2 FACE="Arial">Arup </FONT>
<BR><FONT SIZE=2 FACE="Arial">901 Market Street Suite 260</FONT>
<BR><FONT SIZE=2 FACE="Arial">San Francisco, CA 94103</FONT>
<BR><FONT SIZE=2 FACE="Arial">tel: 415 946 0279</FONT>
<BR><FONT SIZE=2 FACE="Arial">fax: 415 957 9096</FONT>
<BR><FONT SIZE=2 FACE="Arial">taylor.keep@arup.com</FONT>
<BR><A HREF="file://www.arup.com"><U><FONT COLOR="#0000FF" SIZE=2 FACE="Arial">www.arup.com</FONT></U></A>
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