<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"><meta name="Generator" content="Microsoft Word 12 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style></head><body lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal">Hello All,</p><p class="MsoNormal"> </p><p class="MsoNormal">I’ve come across an unexpected result and thought I’d share… maybe someone here can shed some light. I am modeling a VAV air handler with supply and <u>relief</u> fans. </p>
<p class="MsoNormal"> </p><p class="MsoNormal">When I try to enter the design flow of the relief fan (RETURN-FLOW keyword), which is about 90% of the design supply flow, the model forces outside air to be at least 10% (the leftover from 90%) * [supply flow] for all hours that the fans are running, including night cycle hours when I force outside air to 0 using the MIN-AIR-SCH keyword. I believe this behavior is intended for return fans, and I’ve indicated that I want to model a relief fan using the RETURN-FAN-LOC keyword. The increased outside air, affecting all of the night cycle hours and sometimes interfering with DCV control, has a significant effect on simulation results.</p>
<p class="MsoNormal"> </p><p class="MsoNormal">For the project I’m working on, I’ve restored the RETURN-FLOW keyword to default, since I don’t think the effect on the results will be significant. But I’m curious whether anyone else has noticed this, or has any thoughts on the issue?</p>
<p class="MsoNormal"> </p><p class="MsoNormal">Regards,</p><p class="MsoNormal">Mike</p><p class="MsoNormal"> </p><p class="MsoNormal">Mike Karpman</p><p class="MsoNormal"><b><span style="color:#006600">Karpman Consulting</span></b></p>
<p class="MsoNormal">(860) 430-9110</p><p class="MsoNormal">41C New London Turnpike</p><p class="MsoNormal">Glastonbury, CT 06033</p><p class="MsoNormal"> </p></div></body></html>