<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"><DIV>Kevin.</DIV>
<DIV> </DIV>
<DIV>Under the tab of Flow Parameters, you may use Return-Cap-Ratio to specify the return air flowrate. Also, you can check the definition of this parameter to make sure that's what you want.</DIV>
<DIV> </DIV>
<DIV>Hope this helps.<BR></DIV>
<DIV> </DIV>
<DIV>Shaojie</DIV>
<H5>RETURN-CAP-RATIO</H5>
<P class=MsoBodyText>For systems that can have a return fan, specifies the ratio of the return/relief fan capacity to the supply capacity. Applies only when a return fan exists. In many buildings, the return fan is deliberately sized 10% to 20% smaller than the supply fan (RETURN-CAP-RATIO = 0.8 to 0.9) so that the building is pressurized whenever the fans run. The difference between the supply and return air flow exfiltrates from the building (or is exhausted through zone exhaust fans). The default value of 1.0 implies that no building pressurization occurs. The amount assumed to exfiltrate is</DIV>
<P class=MsoBodyTextIndent style="MARGIN: 0pt 0pt 12pt 32.15pt"><SPAN style="FONT-SIZE: 11pt; LETTER-SPACING: -0.25pt">FX = [SUPPLY-FLOW] * (1.0 - [RETURN-CAP-RATIO])</SPAN></DIV>
<P class=MsoBodyText>In other words, the amount exfiltrated due to building pressurization (or zone exhaust) is assumed to be constant all hours of operation. In the hourly simulation, the return/relief fan operates only when the actual return air flow is greater than (FX - zonal exhaust). The return/relief fan moves only the amount of return air greater than FX. If FX is greater than the outside air ventilation requirements, as defined through other keywords, then FX will override any other outside air requirements including those specified through scheduled values. If you have specified the return fan size, a check will be made to see if any building pressurization is occurring. The difference between the supply flow and return flow is compared to the zonal exhaust quantity. If the zonal exhaust quantity is less than this difference, then the balance is assumed to exfiltrate. Note that infiltration is still assumed to occur, as infiltration is
calculated in the LOADS module. For this reason, the infiltration schedules in LOADS should be coordinated with the fan schedules in SYSTEMS. </DIV>
<DIV> </DIV>
<DIV><BR><BR>--- On <B>Mon, 5/11/09, Kevin Kyte <I><kkyte@robsonwoese.com></I></B> wrote:<BR></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(16,16,255) 2px solid">From: Kevin Kyte <kkyte@robsonwoese.com><BR>Subject: [Equest-users] sizing return air flow for an autosized supply air flow<BR>To: "equest-users@lists.onebuilding.org" <equest-users@lists.onebuilding.org><BR>Date: Monday, May 11, 2009, 2:39 PM<BR><BR>
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<P class=MsoNormal>I have seen that something like local(“Supply-Flow”)* .9 will work if the supply air flow is already entered as an input. </DIV>
<P class=MsoNormal>If supply air is autosized, I want return air to be supply air minus outdoor air or 90% of supply air whichever is larger.</DIV>
<P class=MsoNormal> </DIV>
<P class=MsoNormal>Is eQuest capable of generating a return air flow number that is a percentage based on an autosized supply air flow?</DIV>
<P class=MsoNormal> </DIV>
<P class=MsoNormal>Thank You.</DIV>
<P class=MsoNormal> </DIV>
<P class=MsoNormal> </DIV>
<P class=MsoNormal> </DIV>
<P class=MsoNormal><SPAN style="FONT-SIZE: 10.5pt">Kevin Kyte, EIT, </SPAN><SPAN lang=EN style="FONT-SIZE: 10.5pt">LEED®</SPAN></DIV>
<P class=MsoNormal><SPAN lang=EN style="FONT-SIZE: 10.5pt">Jr. Mechanical Engineer</SPAN></DIV>
<P class=MsoNormal><SPAN lang=EN style="FONT-SIZE: 10.5pt">RobsonWoese, Inc.</SPAN></DIV>
<P class=MsoNormal><SPAN lang=EN style="FONT-SIZE: 10.5pt">D: 716.636.1800 x211</SPAN><SPAN style="FONT-SIZE: 10.5pt"></SPAN></DIV>
<P class=MsoNormal> </DIV></DIV><BR>
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