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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Aru,<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 don’t think the intention of G3.1.2.2 is met by oversizing only the plant and not the systems. The 90.1 User’s Manual does not specify what is to be oversized either, although it does describe a chiller when discussing the differences in equipment sizing between the ECB and PRM:<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>“For instance, if a chiller in the proposed building is 50% oversized, then the chiller in the budget building is also 50% oversized. However with the building performance rating method, equipment in the baseline building is oversized by a fixed amount in all cases.”<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 eQUEST, setting the system Cool Sizing Ratio to 1.15 and Heat Sizing Ratio to 1.25 will also increase the autosized capacities of the plant. I believe this is how most Appendix G modelers (including myself) address the G3.1.2.2 requirement.<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'>Note that you could also achieve the same cooling and heating capacity oversizing by setting the overall system Sizing Ratio to 1.15, the Cool Sizing ratio to 1.00 and the Heat Sizing Ratio to 1.087. (1.15x1.087—1.25). However, this oversizes the system airflow by 15%, and G3.1.2.8, which specifies how design airflow rates are determined, does not mention oversizing. I have had models where unmet heating/cooling hours could only be reduced sufficiently by increasing the system airflow as a last resort.<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'>Regards,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Bill<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 width=486 height=116 id="Picture_x0020_1" src="cid:image001.jpg@01CC4B74.11DA23E0" alt="Senior Energy Engineer"><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"'> equest-users-bounces@lists.onebuilding.org [mailto:equest-users-bounces@lists.onebuilding.org] <b>On Behalf Of </b>Arunabha Sau<br><b>Sent:</b> Monday, July 25, 2011 7:47 PM<br><b>To:</b> equest-users@lists.onebuilding.org<br><b>Subject:</b> [Equest-users] Oversizing..AHU or Plant?<o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'>Howdy!</span><o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'>So, I just saw a project which has applied its oversizing factors (1.15 for cooling and 1.25 for heating) to the plant rather than the air handlers. ASHRAE 90.1 Appendix G <span class=apple-style-span>page 180, G3.1.2.2 Equipment capacities does not specify where the oversizing should occur. Have you seen this method used before? Is it an acceptable and accurate way of meeting the baseline modeling requirements?</span></span><o:p></o:p></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'>I appreciate your help.<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'><o:p> </o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'>Much thanks,<o:p></o:p></span></p></div><div><p class=MsoNormal><span style='font-family:"Tahoma","sans-serif"'>Aru<o:p></o:p></span></p></div></div></body></html>