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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'>From your question, I assume you are setting your System Type as one of the “Constant Volume…” system types.<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'>If you’ve selected “Constant Volume – Single Zone” as your system type, then in the System Inputs, “System Components/Supply Fan” input, there is a “Fan Control” option that specifies 1-speed or multiple speed fans. You need to have the “1-speed fan cooling and heating” selected. Otherwise, HAP looks at a lot of other settings and calculates the supply air flow from there.<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'>If you have any of the other “Constant Volume” systems types, then the “Fan Control” options are not available and you are back to having HAP calculate the supply air flows differently for heating and cooling based on things like space temperature, supply air temperature setpoint, heating and cooling loads, etc.<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'>If you have one of the other Constant Volume system types, you may be able to force a constant supply air flow by adjusting the minimum airflows under the “Zone Component/Supply Terminal/Minimum Airflow” settings. I haven’t played with that setting for this application though.<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'>Good luck.<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:"Arial","sans-serif";color:black'>Michael L. Hardy, PE, F.NSPE</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> <br></span><span style='font-size:11.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>Black Oak Engineering, Inc.<br></span><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:black'>Cell 503.314.5244</span><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"'> Hap-users [mailto:hap-users-bounces@lists.onebuilding.org] <b>On Behalf Of </b>Ahmed Kamel<br><b>Sent:</b> Thursday, October 30, 2014 3:14 PM<br><b>To:</b> hap-users@lists.onebuilding.org<br><b>Subject:</b> [Hap-users] Central Heating Question<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>Hello,<br><br>I have a question regarding designing a central heating system and I would like your help.<br><br>Why does my central heating system has less cfm than my central cooling? Shouldn't they be the same since it's the same fan?<br><br>Also, I want to condition my rooms at 70 f during the winter season. Is it okay to set the "design temperature" of the central heating system to 72 f and let the heating loads bring it down to 70 f?<o:p></o:p></span></p></div></div></body></html>